[PATCH v6 0/8] dma: swiotlb: Centralize default pool policy and sizing

[PATCH v6 0/8] dma: swiotlb: Centralize default pool policy and sizing

[Aneesh Kumar K.V (Arm)]

Hi,

This series centralizes swiotlb default-pool selection and sizing, and
simplifies the initialization flags used to describe pool placement.

The first patch replaces the addressing-limit argument with initialization
flags and introduces explicit policies for the different reasons a default
pool may be needed. Architectures now report DMA addressing constraints with
SWIOTLB_INIT_ADDRESSING_LIMIT, while the core selects the corresponding pool
policy.

The second patch moves the reduced sizing used when the pool is needed only
for unaligned kmalloc bouncing from arm64 and RISC-V into the swiotlb core.

The third patch centralizes swiotlb sizing for memory-encrypted systems. It
moves the existing x86 guest-sizing policy into the core. Host memory
encryption retains the normal pool size, and a shared default pool is not
selected solely for guest memory encryption when a restricted DMA pool is
present.

The fourth patch removes SWIOTLB_ANY. Pool placement is derived directly from
SWIOTLB_INIT_ADDRESSING_LIMIT: pools required for limited DMA addressing are
allocated below the architecture's low address limit, while other pools may
be allocated anywhere in directly mapped memory. Xen continues to request a
pool explicitly with SWIOTLB_INIT_REMAP without imposing a low-address
constraint.

Changes from v5:
https://lore.kernel.org/all/20260921063628.362078-1-aneesh.kumar@kernel.org
* Collect Reviewed-by tags.
* Drop the x86 crash changes
* Add two new patches:
  "dma: swiotlb: Consolidate slab rounding"
  "dma: swiotlb: Rename swiotlb_size_or_default()"
* Drop the swiotlb_default_size_changed() helper.
* Simplify swiotlb_adjust_pool_size().

Changes from v4:
https://lore.kernel.org/all/20260914070135.313337-1-aneesh.kumar@kernel.org
* Collect Reviewed-by tags.
* Add a new patch, "dma: swiotlb: Track whether the pool size was explicitly set".
* Retain SWIOTLB_ANY usage for RISC-V until patch 6.
* Rename SWIOTLB_INIT_FORCE_DISABLE to SWIOTLB_INIT_DEFAULT_OFF.

Changes from v3:
https://lore.kernel.org/all/20260904101810.1193505-1-aneesh.kumar@kernel.org
* Add a new patch, "dma: swiotlb: Add an overridable architecture pool opt-out".
* Clarify the change in default behavior with the removal of SWIOTLB_ANY.

Changes from v2:
https://lore.kernel.org/all/20260813102521.1367737-1-aneesh.kumar@kernel.org
* Rebase to latest tree.
* Drop SWIOTLB_ANY and derive that based on SWIOTLB_INIT_ADDRESSING_LIMIT
* Add SWIOTLB_INIT_REMAP.

v1:
https://lore.kernel.org/all/20260811134056.756015-1-aneesh.kumar@kernel.org

Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Suzuki K Poulose <Suzuki.Poulose@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Mostafa Saleh <smostafa@google.com>
Cc: Petr Tesarik <ptesarik@suse.com>
Cc: Alexey Kardashevskiy <aik@amd.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Xu Yilun <yilun.xu@linux.intel.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: "Christophe Leroy (CS GROUP)" <chleroy@kernel.org>
Cc: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
Cc: Shrikanth Hegde <sshegde@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: Paul Walmsley <pjw@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: loongarch@lists.linux.dev
Cc: linux-mips@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-riscv@lists.infradead.org
Cc: linux-s390@vger.kernel.org
Cc: x86@kernel.org

Aneesh Kumar K.V (Arm) (8):
  dma: swiotlb: Rename swiotlb_size_or_default()
  dma: swiotlb: Consolidate slab rounding
  dma: swiotlb: Track whether the pool size was explicitly set
  dma: swiotlb: Centralize default pool policy selection
  dma: swiotlb: Centralize minimal pool sizing
  dma: swiotlb: Centralize memory-encryption pool sizing
  dma: swiotlb: Add an overridable architecture pool opt-out
  dma: swiotlb: Remove SWIOTLB_ANY

 Documentation/core-api/swiotlb.rst   |   8 +-
 arch/arm/mm/init.c                   |   6 +-
 arch/arm/xen/mm.c                    |   2 +-
 arch/arm64/mm/init.c                 |  14 +-
 arch/loongarch/kernel/setup.c        |   2 +-
 arch/mips/cavium-octeon/dma-octeon.c |   2 +-
 arch/mips/loongson64/dma.c           |   2 +-
 arch/mips/sibyte/common/dma.c        |   2 +-
 arch/powerpc/kernel/dma-swiotlb.c    |   4 +-
 arch/powerpc/mm/mem.c                |  17 ++-
 arch/powerpc/platforms/pseries/svm.c |  10 --
 arch/powerpc/sysdev/fsl_pci.c        |   1 +
 arch/riscv/mm/init.c                 |  24 +---
 arch/s390/mm/init.c                  |   2 +-
 arch/x86/include/asm/crash_reserve.h |   4 +-
 arch/x86/kernel/pci-dma.c            |  23 +++-
 arch/x86/mm/mem_encrypt.c            |  24 ----
 include/linux/swiotlb.h              |  17 ++-
 kernel/dma/swiotlb.c                 | 193 +++++++++++++++++++--------
 19 files changed, 210 insertions(+), 147 deletions(-)


base-commit: 704340f1cd0dcef829eb62f5b48ae95a2ce17bdf
-- 
2.43.0

[PATCH v6 1/8] dma: swiotlb: Rename swiotlb_size_or_default()

[Aneesh Kumar K.V (Arm)]

Rename swiotlb_size_or_default() to swiotlb_default_pool_size() to make
clear that it returns the current size of the default SWIOTLB pool.
This includes changes made by command-line options or sizing heuristics,
not just the compiled-in default.

No functional change.

Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Paul Walmsley <pjw@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Thomas Gleixner <tglx@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
 arch/arm/xen/mm.c                    | 2 +-
 arch/arm64/mm/init.c                 | 2 +-
 arch/riscv/mm/init.c                 | 2 +-
 arch/x86/include/asm/crash_reserve.h | 4 ++--
 include/linux/swiotlb.h              | 2 +-
 kernel/dma/swiotlb.c                 | 2 +-
 6 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
index 882cd70c7a2f..a6cf55c6fd55 100644
--- a/arch/arm/xen/mm.c
+++ b/arch/arm/xen/mm.c
@@ -125,7 +125,7 @@ static int __init xen_mm_init(void)
 		return 0;
 
 	/* we can work with the default swiotlb */
-	rc = swiotlb_init_late(swiotlb_size_or_default(),
+	rc = swiotlb_init_late(swiotlb_default_pool_size(),
 			       xen_swiotlb_gfp(), NULL);
 	if (rc < 0)
 		return rc;
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index fbf215ecc7d0..0842098a279b 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -348,7 +348,7 @@ void __init arch_mm_preinit(void)
 		unsigned long size =
 			DIV_ROUND_UP(memblock_phys_mem_size(), 1024);
 
-		swiotlb_adjust_size(min(swiotlb_size_or_default(), size));
+		swiotlb_adjust_size(min(swiotlb_default_pool_size(), size));
 	}
 
 	swiotlb_init(true, flags);
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index fb37b0b67efe..5fa392021717 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -185,7 +185,7 @@ void __init arch_mm_preinit(void)
 		 */
 		unsigned long size =
 			DIV_ROUND_UP(memblock_phys_mem_size(), 1024);
-		swiotlb_adjust_size(min(swiotlb_size_or_default(), size));
+		swiotlb_adjust_size(min(swiotlb_default_pool_size(), size));
 		swiotlb = true;
 		swiotlb_flags |= SWIOTLB_ANY;
 	}
diff --git a/arch/x86/include/asm/crash_reserve.h b/arch/x86/include/asm/crash_reserve.h
index 7835b2cdff04..047f638a766d 100644
--- a/arch/x86/include/asm/crash_reserve.h
+++ b/arch/x86/include/asm/crash_reserve.h
@@ -18,7 +18,7 @@
  * no good way to detect the paging mode of the target kernel which will be
  * loaded for dumping.
  */
-extern unsigned long swiotlb_size_or_default(void);
+extern unsigned long swiotlb_default_pool_size(void);
 
 #ifdef CONFIG_X86_32
 # define CRASH_ADDR_LOW_MAX     SZ_512M
@@ -33,7 +33,7 @@ extern unsigned long swiotlb_size_or_default(void);
 static inline unsigned long crash_low_size_default(void)
 {
 #ifdef CONFIG_X86_64
-	return max(swiotlb_size_or_default() + (8UL << 20), 256UL << 20);
+	return max(swiotlb_default_pool_size() + (8UL << 20), 256UL << 20);
 #else
 	return 0;
 #endif
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 2a421241b980..5f24edf47b68 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -38,7 +38,7 @@ struct scatterlist;
 #define IO_TLB_DEFAULT_SIZE (64UL << 20)
 #endif
 
-unsigned long swiotlb_size_or_default(void);
+unsigned long swiotlb_default_pool_size(void);
 void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags,
 	int (*remap)(void *tlb, unsigned long nslabs));
 int swiotlb_init_late(size_t size, gfp_t gfp_mask,
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index ded7016a46a7..42c51fb57e12 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -285,7 +285,7 @@ setup_io_tlb_npages(char *str)
 }
 early_param("swiotlb", setup_io_tlb_npages);
 
-unsigned long swiotlb_size_or_default(void)
+unsigned long swiotlb_default_pool_size(void)
 {
 	return default_nslabs << IO_TLB_SHIFT;
 }
-- 
2.43.0

[PATCH v6 2/8] dma: swiotlb: Consolidate slab rounding

[Aneesh Kumar K.V (Arm)]

Pass the area count explicitly to swiotlb_calc_nslabs() and keep the
calculation separate from updates to the default_nslabs . Move the
default_nslabs update into swiotlb_adjust_nareas().

Round slabs to a power of two even before the area count is initialized.
For early swiotlb_adjust_size() calls, this moves rounding from area
initialization to size adjustment, so early queries see the rounded
size.

Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
 kernel/dma/swiotlb.c | 44 ++++++++++++++++++++------------------------
 1 file changed, 20 insertions(+), 24 deletions(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 42c51fb57e12..b59dd2a5984e 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -117,27 +117,20 @@ struct io_tlb_area {
 	spinlock_t lock;
 };
 
-/*
- * Round up number of slabs to the next power of 2. The last area is going
- * be smaller than the rest if default_nslabs is not power of two.
- * The number of slot in an area should be a multiple of IO_TLB_SEGSIZE,
- * otherwise a segment may span two or more areas. It conflicts with free
- * contiguous slots tracking: free slots are treated contiguous no matter
- * whether they cross an area boundary.
- *
- * Return true if default_nslabs is rounded up.
- */
-static bool round_up_default_nslabs(void)
+/* Return a power-of-two number of slabs that can be split between areas. */
+static unsigned long swiotlb_calc_nslabs(unsigned long size,
+		unsigned long nareas)
 {
-	if (!default_nareas)
-		return false;
+	unsigned long nslabs;
 
-	if (default_nslabs < IO_TLB_SEGSIZE * default_nareas)
-		default_nslabs = IO_TLB_SEGSIZE * default_nareas;
-	else if (is_power_of_2(default_nslabs))
-		return false;
-	default_nslabs = roundup_pow_of_two(default_nslabs);
-	return true;
+	nslabs = ALIGN(DIV_ROUND_UP(size, IO_TLB_SIZE), IO_TLB_SEGSIZE);
+	if (nareas && nslabs < IO_TLB_SEGSIZE * nareas)
+		nslabs = IO_TLB_SEGSIZE * nareas;
+
+	if (!is_power_of_2(nslabs))
+		nslabs = roundup_pow_of_two(nslabs);
+
+	return nslabs;
 }
 
 /**
@@ -150,6 +143,8 @@ static bool round_up_default_nslabs(void)
  */
 static void swiotlb_adjust_nareas(unsigned int nareas)
 {
+	unsigned long nslabs;
+
 	if (!nareas)
 		nareas = 1;
 	else if (!is_power_of_2(nareas))
@@ -158,9 +153,12 @@ static void swiotlb_adjust_nareas(unsigned int nareas)
 	default_nareas = nareas;
 
 	pr_info("area num %d.\n", nareas);
-	if (round_up_default_nslabs())
+	nslabs = swiotlb_calc_nslabs(default_nslabs << IO_TLB_SHIFT, nareas);
+	if (nslabs != default_nslabs) {
+		default_nslabs = nslabs;
 		pr_info("SWIOTLB bounce buffer size roundup to %luMB",
 			(default_nslabs << IO_TLB_SHIFT) >> 20);
+	}
 }
 
 /**
@@ -300,10 +298,8 @@ void __init swiotlb_adjust_size(unsigned long size)
 	if (default_nslabs != IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT)
 		return;
 
-	size = ALIGN(size, IO_TLB_SIZE);
-	default_nslabs = ALIGN(size >> IO_TLB_SHIFT, IO_TLB_SEGSIZE);
-	if (round_up_default_nslabs())
-		size = default_nslabs << IO_TLB_SHIFT;
+	default_nslabs = swiotlb_calc_nslabs(size, default_nareas);
+	size = default_nslabs << IO_TLB_SHIFT;
 	pr_info("SWIOTLB bounce buffer size adjusted to %luMB", size >> 20);
 }
 
-- 
2.43.0

[PATCH v6 3/8] dma: swiotlb: Track whether the pool size was explicitly set

[Aneesh Kumar K.V (Arm)]

swiotlb_adjust_size() must not override a pool size supplied through the
swiotlb= command-line parameter.

Currently, it determines whether a size was supplied by comparing
default_nslabs with IO_TLB_DEFAULT_SIZE. This fails when the user
explicitly requests the compiled-in default size, allowing the request
to be overwritten by automatic pool sizing.

Record whether swiotlb= supplied a numeric size in swiotlb_cmdline_size_set
and check that flag directly before adjusting the pool size.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
 kernel/dma/swiotlb.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index b59dd2a5984e..61efa3244daa 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -100,6 +100,7 @@ static struct io_tlb_mem io_tlb_default_mem;
 
 static unsigned long default_nslabs = IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT;
 static unsigned long default_nareas;
+static bool swiotlb_cmdline_size_set __initdata;
 
 /**
  * struct io_tlb_area - IO TLB memory area descriptor
@@ -253,6 +254,7 @@ setup_io_tlb_npages(char *str)
 		/* avoid tail segment of size < IO_TLB_SEGSIZE */
 		default_nslabs =
 			ALIGN(simple_strtoul(str, &str, 0), IO_TLB_SEGSIZE);
+		swiotlb_cmdline_size_set = true;
 	}
 	if (*str == ',')
 		++str;
@@ -295,7 +297,7 @@ void __init swiotlb_adjust_size(unsigned long size)
 	 * architectures such as those supporting memory encryption to
 	 * adjust/expand SWIOTLB size for their use.
 	 */
-	if (default_nslabs != IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT)
+	if (swiotlb_cmdline_size_set)
 		return;
 
 	default_nslabs = swiotlb_calc_nslabs(size, default_nareas);
-- 
2.43.0

[PATCH v6 4/8] dma: swiotlb: Centralize default pool policy selection

[Aneesh Kumar K.V (Arm)]

The addressing_limited argument to swiotlb_init() describes only one
reason for allocating a default SWIOTLB pool. A pool may also be needed
for memory encryption, unaligned kmalloc bouncing, or swiotlb=force.

Replace the boolean argument with the SWIOTLB_INIT_ADDRESSING_LIMIT flag
and have architectures report their DMA addressing constraints through
the initialization flags.

Introduce SWIOTLB pool policies and select the policy in the core before
allocating the default pool. This separates the decision to allocate a
pool from the policy used to size it, allowing subsequent changes to
centralize minimal and confidential-guest sizing.

Set the shared-pool state before memory attributes are updated. Also move
the pseries secure-guest setup before swiotlb_init() so its initialization
flags are available when the policy is selected.

Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: "Christophe Leroy (CS GROUP)" <chleroy@kernel.org>
Cc: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
Cc: Shrikanth Hegde <sshegde@linux.ibm.com>
Cc: Paul Walmsley <pjw@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Thomas Gleixner <tglx@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
 arch/arm/mm/init.c                   |  6 +-
 arch/arm64/mm/init.c                 |  5 +-
 arch/loongarch/kernel/setup.c        |  2 +-
 arch/mips/cavium-octeon/dma-octeon.c |  2 +-
 arch/mips/loongson64/dma.c           |  2 +-
 arch/mips/sibyte/common/dma.c        |  2 +-
 arch/powerpc/kernel/dma-swiotlb.c    |  4 +-
 arch/powerpc/mm/mem.c                | 15 ++++-
 arch/powerpc/platforms/pseries/svm.c | 10 ----
 arch/powerpc/sysdev/fsl_pci.c        |  1 +
 arch/riscv/mm/init.c                 |  6 +-
 arch/s390/mm/init.c                  |  2 +-
 arch/x86/kernel/pci-dma.c            | 16 +++--
 include/linux/swiotlb.h              | 12 ++--
 kernel/dma/swiotlb.c                 | 90 ++++++++++++++++++++++------
 15 files changed, 128 insertions(+), 47 deletions(-)

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 0cc1bf04686d..aca97a4e5dcd 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -223,7 +223,11 @@ static inline void poison_init_mem(void *s, size_t count)
 void __init arch_mm_preinit(void)
 {
 #ifdef CONFIG_ARM_LPAE
-	swiotlb_init(max_pfn > arm_dma_pfn_limit, SWIOTLB_VERBOSE);
+	unsigned int flags = SWIOTLB_VERBOSE;
+
+	if (max_pfn > arm_dma_pfn_limit)
+		flags |= SWIOTLB_INIT_ADDRESSING_LIMIT;
+	swiotlb_init(flags);
 #endif
 
 #ifdef CONFIG_SA1111
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 0842098a279b..f55ebe57b8e1 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -351,7 +351,10 @@ void __init arch_mm_preinit(void)
 		swiotlb_adjust_size(min(swiotlb_default_pool_size(), size));
 	}
 
-	swiotlb_init(true, flags);
+	if (max_pfn > PFN_DOWN(arm64_dma_phys_limit))
+		flags |= SWIOTLB_INIT_ADDRESSING_LIMIT;
+
+	swiotlb_init(flags);
 
 	/*
 	 * Check boundaries twice: Some fundamental inconsistencies can be
diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
index 6fa4a22a58fd..02f52f6b2747 100644
--- a/arch/loongarch/kernel/setup.c
+++ b/arch/loongarch/kernel/setup.c
@@ -404,7 +404,7 @@ static void __init arch_mem_init(char **cmdline_p)
 
 	memblock_set_bottom_up(true);
 
-	swiotlb_init(true, SWIOTLB_VERBOSE);
+	swiotlb_init(SWIOTLB_VERBOSE | SWIOTLB_INIT_ADDRESSING_LIMIT);
 
 	dma_contiguous_reserve(PFN_PHYS(max_low_pfn));
 
diff --git a/arch/mips/cavium-octeon/dma-octeon.c b/arch/mips/cavium-octeon/dma-octeon.c
index 9fbba6a8fa4c..ca7c37bc070f 100644
--- a/arch/mips/cavium-octeon/dma-octeon.c
+++ b/arch/mips/cavium-octeon/dma-octeon.c
@@ -235,5 +235,5 @@ void __init plat_swiotlb_setup(void)
 #endif
 
 	swiotlb_adjust_size(swiotlbsize);
-	swiotlb_init(true, SWIOTLB_VERBOSE);
+	swiotlb_init(SWIOTLB_VERBOSE | SWIOTLB_INIT_ADDRESSING_LIMIT);
 }
diff --git a/arch/mips/loongson64/dma.c b/arch/mips/loongson64/dma.c
index 52801442ea86..5b8056e6c5a8 100644
--- a/arch/mips/loongson64/dma.c
+++ b/arch/mips/loongson64/dma.c
@@ -25,5 +25,5 @@ phys_addr_t dma_to_phys(struct device *dev, dma_addr_t daddr)
 
 void __init plat_swiotlb_setup(void)
 {
-	swiotlb_init(true, SWIOTLB_VERBOSE);
+	swiotlb_init(SWIOTLB_VERBOSE | SWIOTLB_INIT_ADDRESSING_LIMIT);
 }
diff --git a/arch/mips/sibyte/common/dma.c b/arch/mips/sibyte/common/dma.c
index c5c2c782aff6..3835fee21489 100644
--- a/arch/mips/sibyte/common/dma.c
+++ b/arch/mips/sibyte/common/dma.c
@@ -10,5 +10,5 @@
 
 void __init plat_swiotlb_setup(void)
 {
-	swiotlb_init(true, SWIOTLB_VERBOSE);
+	swiotlb_init(SWIOTLB_VERBOSE | SWIOTLB_INIT_ADDRESSING_LIMIT);
 }
diff --git a/arch/powerpc/kernel/dma-swiotlb.c b/arch/powerpc/kernel/dma-swiotlb.c
index ba256c37bcc0..97fffa46f05a 100644
--- a/arch/powerpc/kernel/dma-swiotlb.c
+++ b/arch/powerpc/kernel/dma-swiotlb.c
@@ -14,8 +14,10 @@ unsigned int ppc_swiotlb_flags;
 
 void __init swiotlb_detect_4g(void)
 {
-	if ((memblock_end_of_DRAM() - 1) > 0xffffffff)
+	if ((memblock_end_of_DRAM() - 1) > 0xffffffff) {
 		ppc_swiotlb_enable = 1;
+		ppc_swiotlb_flags |= SWIOTLB_INIT_ADDRESSING_LIMIT;
+	}
 }
 
 static int __init check_swiotlb_enabled(void)
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index b617b69452cd..006ed41097e9 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -287,6 +287,19 @@ void __init arch_mm_preinit(void)
 	BUILD_BUG_ON(MMU_PAGE_COUNT > 16);
 
 #ifdef CONFIG_SWIOTLB
+	if (is_secure_guest()) {
+
+		/* Don't release the SWIOTLB buffer. */
+		ppc_swiotlb_enable = 1;
+
+		/*
+		 * Since the guest memory is inaccessible to the host,
+		 * devices always need to use the SWIOTLB buffer for DMA
+		 * even if dma_capable() says otherwise.
+		 */
+		ppc_swiotlb_flags |= SWIOTLB_ANY;
+	}
+
 	/*
 	 * Some platforms (e.g. 85xx) limit DMA-able memory way below
 	 * 4G. We force memblock to bottom-up mode to ensure that the
@@ -295,7 +308,7 @@ void __init arch_mm_preinit(void)
 	 * back to to-down.
 	 */
 	memblock_set_bottom_up(true);
-	swiotlb_init(ppc_swiotlb_enable, ppc_swiotlb_flags);
+	swiotlb_init(ppc_swiotlb_flags);
 #endif
 
 	kasan_late_init();
diff --git a/arch/powerpc/platforms/pseries/svm.c b/arch/powerpc/platforms/pseries/svm.c
index 7a403dbd35ee..4a0be631dc6d 100644
--- a/arch/powerpc/platforms/pseries/svm.c
+++ b/arch/powerpc/platforms/pseries/svm.c
@@ -21,16 +21,6 @@ static int __init init_svm(void)
 	if (!is_secure_guest())
 		return 0;
 
-	/* Don't release the SWIOTLB buffer. */
-	ppc_swiotlb_enable = 1;
-
-	/*
-	 * Since the guest memory is inaccessible to the host, devices always
-	 * need to use the SWIOTLB buffer for DMA even if dma_capable() says
-	 * otherwise.
-	 */
-	ppc_swiotlb_flags |= SWIOTLB_ANY;
-
 	/* Share the SWIOTLB buffer with the host. */
 	swiotlb_update_mem_attributes();
 
diff --git a/arch/powerpc/sysdev/fsl_pci.c b/arch/powerpc/sysdev/fsl_pci.c
index 600f83cea1cd..49264e25108b 100644
--- a/arch/powerpc/sysdev/fsl_pci.c
+++ b/arch/powerpc/sysdev/fsl_pci.c
@@ -444,6 +444,7 @@ static void setup_pci_atmu(struct pci_controller *hose)
 	if (hose->dma_window_size < mem) {
 #ifdef CONFIG_SWIOTLB
 		ppc_swiotlb_enable = 1;
+		ppc_swiotlb_flags |= SWIOTLB_INIT_ADDRESSING_LIMIT;
 #else
 		pr_err("%pOF: ERROR: Memory size exceeds PCI ATMU ability to "
 			"map - enable CONFIG_SWIOTLB to avoid dma errors.\n",
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 5fa392021717..2562cf45a8f2 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -190,7 +190,11 @@ void __init arch_mm_preinit(void)
 		swiotlb_flags |= SWIOTLB_ANY;
 	}
 
-	swiotlb_init(swiotlb, swiotlb_flags);
+	if ((max_pfn > PFN_DOWN(dma32_phys_limit)) &&
+	     (memblock_start_of_DRAM() < dma32_phys_limit))
+		swiotlb_flags |= SWIOTLB_INIT_ADDRESSING_LIMIT;
+
+	swiotlb_init(swiotlb_flags);
 
 	print_vm_layout();
 }
diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index be7e009e7b59..78f507e24ceb 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -166,7 +166,7 @@ static void __init pv_init(void)
 	virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
 
 	/* make sure bounce buffers are shared */
-	swiotlb_init(true, SWIOTLB_VERBOSE | SWIOTLB_ANY);
+	swiotlb_init(SWIOTLB_VERBOSE | SWIOTLB_ANY);
 	swiotlb_update_mem_attributes();
 }
 
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 75cf8f6ae8cd..0cff255827ba 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -44,8 +44,10 @@ static unsigned int x86_swiotlb_flags;
 static void __init pci_swiotlb_detect(void)
 {
 	/* don't initialize swiotlb if iommu=off (no_iommu=1) */
-	if (!no_iommu && max_possible_pfn > MAX_DMA32_PFN)
+	if (!no_iommu && max_possible_pfn > MAX_DMA32_PFN) {
 		x86_swiotlb_enable = true;
+		x86_swiotlb_flags |= SWIOTLB_INIT_ADDRESSING_LIMIT;
+	}
 
 	/*
 	 * Set swiotlb to 1 so that bounce buffers are allocated and used for
@@ -81,8 +83,10 @@ static void __init pci_xen_swiotlb_init(void)
 	if (!xen_swiotlb_enabled())
 		return;
 	x86_swiotlb_enable = true;
-	x86_swiotlb_flags |= SWIOTLB_ANY;
-	swiotlb_init_remap(true, x86_swiotlb_flags, xen_swiotlb_fixup);
+	/* Xen can use a SWIOTLB pool anywhere in directly mapped memory. */
+	x86_swiotlb_flags &= ~SWIOTLB_INIT_ADDRESSING_LIMIT;
+	x86_swiotlb_flags |= SWIOTLB_INIT_REMAP | SWIOTLB_ANY;
+	swiotlb_init_remap(x86_swiotlb_flags, xen_swiotlb_fixup);
 	dma_ops = &xen_swiotlb_dma_ops;
 	if (IS_ENABLED(CONFIG_PCI))
 		pci_request_acs();
@@ -103,7 +107,7 @@ void __init pci_iommu_alloc(void)
 	gart_iommu_hole_init();
 	amd_iommu_detect();
 	detect_intel_iommu();
-	swiotlb_init(x86_swiotlb_enable, x86_swiotlb_flags);
+	swiotlb_init(x86_swiotlb_flags);
 }
 
 static __init int iommu_setup(char *p)
@@ -149,8 +153,10 @@ static __init int iommu_setup(char *p)
 			return 1;
 		}
 #ifdef CONFIG_SWIOTLB
-		if (!strncmp(p, "soft", 4))
+		if (!strncmp(p, "soft", 4)) {
 			x86_swiotlb_enable = true;
+			x86_swiotlb_flags |= SWIOTLB_INIT_ADDRESSING_LIMIT;
+		}
 #endif
 		if (!strncmp(p, "pt", 2))
 			iommu_set_default_passthrough(true);
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 5f24edf47b68..6386536a5ec6 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -16,6 +16,10 @@ struct scatterlist;
 
 #define SWIOTLB_VERBOSE	(1 << 0) /* verbose initialization */
 #define SWIOTLB_ANY	(1 << 1) /* allow any memory for the buffer */
+/* Initialize a default-sized pool for devices with limited DMA addressing. */
+#define SWIOTLB_INIT_ADDRESSING_LIMIT	(1 << 2)
+/* Initialize a default-sized pool that requires architecture remapping. */
+#define SWIOTLB_INIT_REMAP		(1 << 3)
 
 /*
  * Maximum allowable number of contiguous slabs to map,
@@ -39,8 +43,8 @@ struct scatterlist;
 #endif
 
 unsigned long swiotlb_default_pool_size(void);
-void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags,
-	int (*remap)(void *tlb, unsigned long nslabs));
+void __init swiotlb_init_remap(unsigned int flags,
+			       int (*remap)(void *tlb, unsigned long nslabs));
 int swiotlb_init_late(size_t size, gfp_t gfp_mask,
 	int (*remap)(void *tlb, unsigned long nslabs));
 extern void __init swiotlb_update_mem_attributes(void);
@@ -183,7 +187,7 @@ static inline bool is_swiotlb_force_bounce(struct device *dev)
 	return mem && mem->force_bounce;
 }
 
-void swiotlb_init(bool addressing_limited, unsigned int flags);
+void swiotlb_init(unsigned int flags);
 void __init swiotlb_exit(void);
 void swiotlb_dev_init(struct device *dev);
 size_t swiotlb_max_mapping_size(struct device *dev);
@@ -193,7 +197,7 @@ void __init swiotlb_adjust_size(unsigned long size);
 phys_addr_t default_swiotlb_base(void);
 phys_addr_t default_swiotlb_limit(void);
 #else
-static inline void swiotlb_init(bool addressing_limited, unsigned int flags)
+static inline void swiotlb_init(unsigned int flags)
 {
 }
 
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 61efa3244daa..8ae315b2d0e7 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -81,6 +81,13 @@ struct io_tlb_slot {
 static bool swiotlb_force_bounce;
 static bool swiotlb_force_disable;
 
+enum swiotlb_pool_policy {
+	SWIOTLB_POOL_NONE,
+	SWIOTLB_POOL_MINIMAL,
+	SWIOTLB_POOL_DEFAULT,
+	SWIOTLB_POOL_CC_GUEST,
+};
+
 #ifdef CONFIG_SWIOTLB_DYNAMIC
 
 static void swiotlb_dyn_alloc(struct work_struct *work);
@@ -354,24 +361,15 @@ static void swiotlb_mark_pool_used(struct io_tlb_pool *pool)
 void __init swiotlb_update_mem_attributes(void)
 {
 	struct io_tlb_pool *mem = &io_tlb_default_mem.defpool;
-	unsigned long bytes;
-
-	/*
-	 * if platform support memory encryption, swiotlb buffers are
-	 * shared by default.
-	 */
-	if (cc_platform_has(CC_ATTR_MEM_ENCRYPT))
-		io_tlb_default_mem.cc_shared = true;
-	else
-		io_tlb_default_mem.cc_shared = false;
 
 	if (!mem->nslabs || mem->late_alloc)
 		return;
-	bytes = PAGE_ALIGN(mem->nslabs << IO_TLB_SHIFT);
 
 	if (io_tlb_default_mem.cc_shared) {
 		int ret;
+		unsigned long bytes;
 
+		bytes = PAGE_ALIGN(mem->nslabs << IO_TLB_SHIFT);
 		ret = set_memory_decrypted((unsigned long)mem->vaddr,
 					   bytes >> PAGE_SHIFT);
 		if (ret) {
@@ -462,22 +460,72 @@ static void __init *swiotlb_memblock_alloc(unsigned long nslabs,
 	return tlb;
 }
 
+static bool __init swiotlb_kmalloc_needs_bounce(void)
+{
+	return IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) &&
+	       (dma_get_cache_alignment() > 1);
+}
+
+static void __init
+swiotlb_adjust_pool_size(enum swiotlb_pool_policy policy)
+{
+	switch (policy) {
+	case SWIOTLB_POOL_MINIMAL:
+		return;
+	case SWIOTLB_POOL_CC_GUEST:
+		return;
+	case SWIOTLB_POOL_NONE:
+		WARN(true, "Cannot adjust SWIOTLB size without a pool\n");
+		return;
+	case SWIOTLB_POOL_DEFAULT:
+	default:
+		return;
+	}
+}
+
+static enum swiotlb_pool_policy __init
+swiotlb_select_pool_policy(unsigned int flags)
+{
+	if (swiotlb_force_disable)
+		return SWIOTLB_POOL_NONE;
+
+	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
+		return SWIOTLB_POOL_CC_GUEST;
+
+	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))
+		return SWIOTLB_POOL_DEFAULT;
+
+	if (flags & SWIOTLB_INIT_REMAP)
+		return SWIOTLB_POOL_DEFAULT;
+
+	if (flags & SWIOTLB_INIT_ADDRESSING_LIMIT)
+		return SWIOTLB_POOL_DEFAULT;
+
+	if (swiotlb_force_bounce)
+		return SWIOTLB_POOL_DEFAULT;
+
+	if (swiotlb_kmalloc_needs_bounce())
+		return SWIOTLB_POOL_MINIMAL;
+
+	return SWIOTLB_POOL_NONE;
+}
+
 /*
  * Statically reserve bounce buffer space and initialize bounce buffer data
  * structures for the software IO TLB used to implement the DMA API.
  */
-void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags,
-		int (*remap)(void *tlb, unsigned long nslabs))
+void __init swiotlb_init_remap(unsigned int flags,
+			       int (*remap)(void *tlb, unsigned long nslabs))
 {
 	struct io_tlb_pool *mem = &io_tlb_default_mem.defpool;
+	enum swiotlb_pool_policy policy;
 	unsigned long nslabs;
 	unsigned int nareas;
 	size_t alloc_size;
 	void *tlb;
 
-	if (!addressing_limit && !swiotlb_force_bounce)
-		return;
-	if (swiotlb_force_disable)
+	policy = swiotlb_select_pool_policy(flags);
+	if (policy == SWIOTLB_POOL_NONE)
 		return;
 
 	io_tlb_default_mem.force_bounce = swiotlb_force_bounce;
@@ -491,6 +539,12 @@ void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags,
 		io_tlb_default_mem.phys_limit = ARCH_LOW_ADDRESS_LIMIT;
 #endif
 
+	/* if we have host or guest memory encryption */
+	if (cc_platform_has(CC_ATTR_MEM_ENCRYPT))
+		io_tlb_default_mem.cc_shared = true;
+
+	swiotlb_adjust_pool_size(policy);
+
 	if (!default_nareas)
 		swiotlb_adjust_nareas(num_possible_cpus());
 
@@ -531,9 +585,9 @@ void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags,
 		swiotlb_print_info();
 }
 
-void __init swiotlb_init(bool addressing_limit, unsigned int flags)
+void __init swiotlb_init(unsigned int flags)
 {
-	swiotlb_init_remap(addressing_limit, flags, NULL);
+	swiotlb_init_remap(flags, NULL);
 }
 
 /*
-- 
2.43.0

[PATCH v6 5/8] dma: swiotlb: Centralize minimal pool sizing

[Aneesh Kumar K.V (Arm)]

A default SWIOTLB pool used only for unaligned kmalloc bouncing can be
smaller than one required for limited DMA addressing. Arm64 and RISC-V
currently implement this sizing independently, using 1 MiB of SWIOTLB
space per GiB of RAM.

The SWIOTLB core now identifies this case with SWIOTLB_POOL_MINIMAL.
Size that policy in swiotlb_adjust_pool_size() and remove the
architecture-specific adjustments.

Explicit swiotlb= sizing remains unchanged because swiotlb_adjust_size()
preserves a user-configured size.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Paul Walmsley <pjw@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
 arch/arm64/mm/init.c | 11 -----------
 arch/riscv/mm/init.c |  4 ----
 kernel/dma/swiotlb.c |  9 ++++++++-
 3 files changed, 8 insertions(+), 16 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index f55ebe57b8e1..95075b5c8207 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -340,17 +340,6 @@ void __init arch_mm_preinit(void)
 {
 	unsigned int flags = SWIOTLB_VERBOSE;
 
-	if (max_pfn <= PFN_DOWN(arm64_dma_phys_limit)) {
-		/*
-		 * If no bouncing needed for ZONE_DMA, reduce the swiotlb
-		 * buffer for kmalloc() bouncing to 1MB per 1GB of RAM.
-		 */
-		unsigned long size =
-			DIV_ROUND_UP(memblock_phys_mem_size(), 1024);
-
-		swiotlb_adjust_size(min(swiotlb_default_pool_size(), size));
-	}
-
 	if (max_pfn > PFN_DOWN(arm64_dma_phys_limit))
 		flags |= SWIOTLB_INIT_ADDRESSING_LIMIT;
 
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 2562cf45a8f2..96856114b387 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -183,10 +183,6 @@ void __init arch_mm_preinit(void)
 		 * memory when DRAM starts above dma32_phys_limit.  Allocate
 		 * ~1 MB per 1 GB of RAM.
 		 */
-		unsigned long size =
-			DIV_ROUND_UP(memblock_phys_mem_size(), 1024);
-		swiotlb_adjust_size(min(swiotlb_default_pool_size(), size));
-		swiotlb = true;
 		swiotlb_flags |= SWIOTLB_ANY;
 	}
 
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 8ae315b2d0e7..75ee63cd354e 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -469,9 +469,14 @@ static bool __init swiotlb_kmalloc_needs_bounce(void)
 static void __init
 swiotlb_adjust_pool_size(enum swiotlb_pool_policy policy)
 {
+	unsigned long size;
+
 	switch (policy) {
 	case SWIOTLB_POOL_MINIMAL:
-		return;
+		/* Use 1MB per 1GB of RAM for kmalloc() bouncing. */
+		size = DIV_ROUND_UP(memblock_phys_mem_size(), 1024);
+		size = min(swiotlb_default_pool_size(), size);
+		break;
 	case SWIOTLB_POOL_CC_GUEST:
 		return;
 	case SWIOTLB_POOL_NONE:
@@ -481,6 +486,8 @@ swiotlb_adjust_pool_size(enum swiotlb_pool_policy policy)
 	default:
 		return;
 	}
+
+	swiotlb_adjust_size(size);
 }
 
 static enum swiotlb_pool_policy __init
-- 
2.43.0

[PATCH v6 6/8] dma: swiotlb: Centralize memory-encryption pool sizing

[Aneesh Kumar K.V (Arm)]

Memory-encrypted guests use shared or unencrypted memory for DMA and may
route all DMA through SWIOTLB. The default pool can therefore be too
small for I/O-intensive workloads.

Move the existing x86 guest-sizing policy into the SWIOTLB core. For
SWIOTLB_POOL_CC_GUEST, size the pool to 6% of guest memory, clamped
between the normal default and 1 GiB. Preserve an explicit swiotlb=
size.

Host memory encryption still selects a normal-sized shared pool and
does not use the guest-sizing policy.

A restricted DMA pool already provides shared bounce buffers for its
devices. Record its presence during reserved-memory initialization and
do not select the confidential-guest default-pool policy solely because
guest memory encryption is active.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
 arch/x86/mm/mem_encrypt.c | 24 ------------------------
 kernel/dma/swiotlb.c      | 27 +++++++++++++++++++++++++--
 2 files changed, 25 insertions(+), 26 deletions(-)

diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index 95bae74fdab2..912f22ca838f 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -101,9 +101,6 @@ void __init mem_encrypt_init(void)
 
 void __init mem_encrypt_setup_arch(void)
 {
-	phys_addr_t total_mem = memblock_phys_mem_size();
-	unsigned long size;
-
 	/*
 	 * Do RMP table fixups after the e820 tables have been setup by
 	 * e820__memory_setup().
@@ -114,27 +111,6 @@ void __init mem_encrypt_setup_arch(void)
 	if (!cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
 		return;
 
-	/*
-	 * For SEV and TDX, all DMA has to occur via shared/unencrypted pages.
-	 * Kernel uses SWIOTLB to make this happen without changing device
-	 * drivers. However, depending on the workload being run, the
-	 * default 64MB of SWIOTLB may not be enough and SWIOTLB may
-	 * run out of buffers for DMA, resulting in I/O errors and/or
-	 * performance degradation especially with high I/O workloads.
-	 *
-	 * Adjust the default size of SWIOTLB using a percentage of guest
-	 * memory for SWIOTLB buffers. Also, as the SWIOTLB bounce buffer
-	 * memory is allocated from low memory, ensure that the adjusted size
-	 * is within the limits of low available memory.
-	 *
-	 * The percentage of guest memory used here for SWIOTLB buffers
-	 * is more of an approximation of the static adjustment which
-	 * 64MB for <1G, and ~128M to 256M for 1G-to-4G, i.e., the 6%
-	 */
-	size = total_mem * 6 / 100;
-	size = clamp_val(size, IO_TLB_DEFAULT_SIZE, SZ_1G);
-	swiotlb_adjust_size(size);
-
 	/* Set restricted memory access for virtio. */
 	virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
 }
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 75ee63cd354e..e626cca63ad1 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -33,6 +33,7 @@
 #include <linux/kmsan-checks.h>
 #include <linux/iommu-helper.h>
 #include <linux/init.h>
+#include <linux/math64.h>
 #include <linux/memblock.h>
 #include <linux/mm.h>
 #include <linux/pfn.h>
@@ -80,6 +81,7 @@ struct io_tlb_slot {
 
 static bool swiotlb_force_bounce;
 static bool swiotlb_force_disable;
+static bool restricted_dma_pool_present __initdata;
 
 enum swiotlb_pool_policy {
 	SWIOTLB_POOL_NONE,
@@ -478,7 +480,25 @@ swiotlb_adjust_pool_size(enum swiotlb_pool_policy policy)
 		size = min(swiotlb_default_pool_size(), size);
 		break;
 	case SWIOTLB_POOL_CC_GUEST:
-		return;
+		/*
+		 * For SEV and TDX and CCA, all DMA has to occur via
+		 * shared/unencrypted pages. Kernel uses SWIOTLB to make this
+		 * happen without changing device drivers. However, depending on
+		 * the workload being run, the default 64MB of SWIOTLB may not be
+		 * enough and SWIOTLB may run out of buffers for DMA, resulting in
+		 * I/O errors and/or performance degradation especially with high
+		 * I/O workloads.
+		 *
+		 * Adjust the default size of SWIOTLB using a percentage of guest
+		 * memory for SWIOTLB buffers.
+		 *
+		 * The percentage of guest memory used here for SWIOTLB buffers is
+		 * more of an approximation of the static adjustment which 64MB for
+		 * <1G, and ~128M to 256M for 1G-to-4G, i.e., the 6%
+		 */
+		size = div_u64((u64)memblock_phys_mem_size() * 6, 100);
+		size = clamp_val(size, IO_TLB_DEFAULT_SIZE, SZ_1G);
+		break;
 	case SWIOTLB_POOL_NONE:
 		WARN(true, "Cannot adjust SWIOTLB size without a pool\n");
 		return;
@@ -496,7 +516,8 @@ swiotlb_select_pool_policy(unsigned int flags)
 	if (swiotlb_force_disable)
 		return SWIOTLB_POOL_NONE;
 
-	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
+	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT) &&
+	    !restricted_dma_pool_present)
 		return SWIOTLB_POOL_CC_GUEST;
 
 	if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))
@@ -2142,6 +2163,8 @@ static int __init rmem_swiotlb_setup(unsigned long node,
 	    of_get_flat_dt_prop(node, "no-map", NULL))
 		return -EINVAL;
 
+	restricted_dma_pool_present = true;
+
 	pr_info("Reserved memory: created restricted DMA pool at %pa, size %ld MiB\n",
 		&rmem->base, (unsigned long)rmem->size / SZ_1M);
 	return 0;
-- 
2.43.0

[PATCH v6 7/8] dma: swiotlb: Add an overridable architecture pool opt-out

[Aneesh Kumar K.V (Arm)]

On x86, iommu=off historically prevented SWIOTLB initialization by not
setting SWIOTLB_INIT_ADDRESSING_LIMIT. This overloads that flag: it
controls both whether a pool is selected and where the pool is
allocated. If another requirement, swiotlb=force selects a pool
independently, omitting SWIOTLB_INIT_ADDRESSING_LIMIT may place it above
the addressable range of devices which need bounce buffering.

Add SWIOTLB_INIT_DEFAULT_OFF to let an architecture opt out of normal
pool initialization without discarding the pool placement constraints.

Unlike swiotlb_force_disable, which is set by swiotlb=noforce and
unconditionally prevents pool initialization, the new flag is an
architecture default. Explicit requirements such as memory encryption,
architecture remapping, or swiotlb=force take precedence over it.

iommu=soft retains SWIOTLB_INIT_ADDRESSING_LIMIT because it requests
software bounce buffering for devices whose DMA masks cannot address all
system memory. Such devices must be able to reach the bounce pool.

Clear both flags for Xen because Xen explicitly requires a remapped
swiotlb pool and may allocate it anywhere in directly mapped memory.

With no override, iommu=off disables both hardware IOMMU translation and
swiotlb bouncing. Direct DMA remains available; mappings outside a
device's addressable range fail instead of being bounced.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Thomas Gleixner <tglx@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
 arch/x86/kernel/pci-dma.c | 11 ++++++++---
 include/linux/swiotlb.h   |  2 ++
 kernel/dma/swiotlb.c      | 10 ++++++++--
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 0cff255827ba..ce257b20ea9c 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -44,9 +44,13 @@ static unsigned int x86_swiotlb_flags;
 static void __init pci_swiotlb_detect(void)
 {
 	/* don't initialize swiotlb if iommu=off (no_iommu=1) */
-	if (!no_iommu && max_possible_pfn > MAX_DMA32_PFN) {
-		x86_swiotlb_enable = true;
+	if (no_iommu)
+		x86_swiotlb_flags |= SWIOTLB_INIT_DEFAULT_OFF;
+
+	if (max_possible_pfn > MAX_DMA32_PFN) {
 		x86_swiotlb_flags |= SWIOTLB_INIT_ADDRESSING_LIMIT;
+		if (!no_iommu)
+			x86_swiotlb_enable = true;
 	}
 
 	/*
@@ -84,7 +88,8 @@ static void __init pci_xen_swiotlb_init(void)
 		return;
 	x86_swiotlb_enable = true;
 	/* Xen can use a SWIOTLB pool anywhere in directly mapped memory. */
-	x86_swiotlb_flags &= ~SWIOTLB_INIT_ADDRESSING_LIMIT;
+	x86_swiotlb_flags &= ~(SWIOTLB_INIT_ADDRESSING_LIMIT |
+			       SWIOTLB_INIT_DEFAULT_OFF);
 	x86_swiotlb_flags |= SWIOTLB_INIT_REMAP | SWIOTLB_ANY;
 	swiotlb_init_remap(x86_swiotlb_flags, xen_swiotlb_fixup);
 	dma_ops = &xen_swiotlb_dma_ops;
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 6386536a5ec6..f5ce45f2994b 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -20,6 +20,8 @@ struct scatterlist;
 #define SWIOTLB_INIT_ADDRESSING_LIMIT	(1 << 2)
 /* Initialize a default-sized pool that requires architecture remapping. */
 #define SWIOTLB_INIT_REMAP		(1 << 3)
+/* Do not initialize a pool unless SWIOTLB is explicitly required. */
+#define SWIOTLB_INIT_DEFAULT_OFF		(1 << 4)
 
 /*
  * Maximum allowable number of contiguous slabs to map,
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index e626cca63ad1..130a13eb85b0 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -526,10 +526,16 @@ swiotlb_select_pool_policy(unsigned int flags)
 	if (flags & SWIOTLB_INIT_REMAP)
 		return SWIOTLB_POOL_DEFAULT;
 
-	if (flags & SWIOTLB_INIT_ADDRESSING_LIMIT)
+	if (swiotlb_force_bounce)
 		return SWIOTLB_POOL_DEFAULT;
 
-	if (swiotlb_force_bounce)
+	/*
+	 * Explicit requirements above override an architecture's default opt-out.
+	 */
+	if (flags & SWIOTLB_INIT_DEFAULT_OFF)
+		return SWIOTLB_POOL_NONE;
+
+	if (flags & SWIOTLB_INIT_ADDRESSING_LIMIT)
 		return SWIOTLB_POOL_DEFAULT;
 
 	if (swiotlb_kmalloc_needs_bounce())
-- 
2.43.0

[PATCH v6 8/8] dma: swiotlb: Remove SWIOTLB_ANY

[Aneesh Kumar K.V (Arm)]

swiotlb pools are currently allocated below the architecture's low
address limit by default. SWIOTLB_ANY overrides this and permits
allocation anywhere in directly mapped memory.

SWIOTLB_INIT_ADDRESSING_LIMIT now explicitly identifies callers which
need a pool that is reachable by devices with limited DMA addressing.
Use it as the placement constraint and remove SWIOTLB_ANY.

This changes the default behavior for callers which do not set either
flag. Previously, omitting SWIOTLB_ANY placed the default pool below the
architecture's low address limit and also constrained dynamically
allocated pools to the same range. After this change, omitting
SWIOTLB_INIT_ADDRESSING_LIMIT permits both static and dynamic pools to
use any directly mapped memory.

Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: "Christophe Leroy (CS GROUP)" <chleroy@kernel.org>
Cc: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
Cc: Shrikanth Hegde <sshegde@linux.ibm.com>
Cc: Paul Walmsley <pjw@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Thomas Gleixner <tglx@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
 Documentation/core-api/swiotlb.rst |  8 ++++----
 arch/powerpc/mm/mem.c              |  6 ++++--
 arch/riscv/mm/init.c               | 16 ----------------
 arch/s390/mm/init.c                |  2 +-
 arch/x86/kernel/pci-dma.c          |  2 +-
 include/linux/swiotlb.h            |  7 +++----
 kernel/dma/swiotlb.c               | 17 ++++++-----------
 7 files changed, 19 insertions(+), 39 deletions(-)

diff --git a/Documentation/core-api/swiotlb.rst b/Documentation/core-api/swiotlb.rst
index 71b4e4c27eb5..06d9f88fdf7b 100644
--- a/Documentation/core-api/swiotlb.rst
+++ b/Documentation/core-api/swiotlb.rst
@@ -148,10 +148,10 @@ may also be adjusted
 due to other conditions, such as running in a CoCo VM, as described above. If
 CONFIG_SWIOTLB_DYNAMIC is enabled, additional pools may be allocated later in
 the life of the system. Each pool must be a contiguous range of physical
-memory. The default pool is allocated below the 4 GiB physical address line so
-it works for devices that can only address 32-bits of physical memory (unless
-architecture-specific code provides the SWIOTLB_ANY flag). In a CoCo VM, the
-pool memory must be decrypted before swiotlb is used.
+memory. The default pool is allocated below the architecture's low address
+limit when it is needed for devices with limited DMA addressing. Otherwise,
+it may be allocated anywhere in directly mapped memory. In a CoCo VM, the pool
+memory must be decrypted before swiotlb is used.
 
 Each pool is divided into "slots" of size IO_TLB_SIZE, which is 2 KiB with
 current definitions. IO_TLB_SEGSIZE contiguous slots (128 slots) constitute
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 006ed41097e9..1bdea6c03848 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -295,9 +295,11 @@ void __init arch_mm_preinit(void)
 		/*
 		 * Since the guest memory is inaccessible to the host,
 		 * devices always need to use the SWIOTLB buffer for DMA
-		 * even if dma_capable() says otherwise.
+		 * even if dma_capable() says otherwise. The hypervisor has
+		 * no addressing limitation, so the buffer may be allocated
+		 * anywhere.
 		 */
-		ppc_swiotlb_flags |= SWIOTLB_ANY;
+		ppc_swiotlb_flags &= ~SWIOTLB_INIT_ADDRESSING_LIMIT;
 	}
 
 	/*
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 96856114b387..734712230f35 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -165,27 +165,11 @@ static void print_vm_layout(void) { }
 
 void __init arch_mm_preinit(void)
 {
-	bool swiotlb = max_pfn > PFN_DOWN(dma32_phys_limit) &&
-		       memblock_start_of_DRAM() < dma32_phys_limit;
 	unsigned int swiotlb_flags = SWIOTLB_VERBOSE;
 #ifdef CONFIG_FLATMEM
 	BUG_ON(!mem_map);
 #endif /* CONFIG_FLATMEM */
 
-	if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) && !swiotlb &&
-	    dma_cache_alignment != 1) {
-		/*
-		 * No 32-bit DMA bouncing needed (either all DRAM is within
-		 * the 32-bit limit, or it all starts above it), but
-		 * kmalloc() buffers whose sizes are not cache-line-aligned
-		 * still require bouncing for non-coherent DMA.  Use
-		 * SWIOTLB_ANY so that the buffer can be allocated from high
-		 * memory when DRAM starts above dma32_phys_limit.  Allocate
-		 * ~1 MB per 1 GB of RAM.
-		 */
-		swiotlb_flags |= SWIOTLB_ANY;
-	}
-
 	if ((max_pfn > PFN_DOWN(dma32_phys_limit)) &&
 	     (memblock_start_of_DRAM() < dma32_phys_limit))
 		swiotlb_flags |= SWIOTLB_INIT_ADDRESSING_LIMIT;
diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 78f507e24ceb..ce10292447f1 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -166,7 +166,7 @@ static void __init pv_init(void)
 	virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc);
 
 	/* make sure bounce buffers are shared */
-	swiotlb_init(SWIOTLB_VERBOSE | SWIOTLB_ANY);
+	swiotlb_init(SWIOTLB_VERBOSE);
 	swiotlb_update_mem_attributes();
 }
 
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index ce257b20ea9c..74e92b457758 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -90,7 +90,7 @@ static void __init pci_xen_swiotlb_init(void)
 	/* Xen can use a SWIOTLB pool anywhere in directly mapped memory. */
 	x86_swiotlb_flags &= ~(SWIOTLB_INIT_ADDRESSING_LIMIT |
 			       SWIOTLB_INIT_DEFAULT_OFF);
-	x86_swiotlb_flags |= SWIOTLB_INIT_REMAP | SWIOTLB_ANY;
+	x86_swiotlb_flags |= SWIOTLB_INIT_REMAP;
 	swiotlb_init_remap(x86_swiotlb_flags, xen_swiotlb_fixup);
 	dma_ops = &xen_swiotlb_dma_ops;
 	if (IS_ENABLED(CONFIG_PCI))
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index f5ce45f2994b..3c3f9d93d400 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -15,13 +15,12 @@ struct page;
 struct scatterlist;
 
 #define SWIOTLB_VERBOSE	(1 << 0) /* verbose initialization */
-#define SWIOTLB_ANY	(1 << 1) /* allow any memory for the buffer */
 /* Initialize a default-sized pool for devices with limited DMA addressing. */
-#define SWIOTLB_INIT_ADDRESSING_LIMIT	(1 << 2)
+#define SWIOTLB_INIT_ADDRESSING_LIMIT	(1 << 1)
 /* Initialize a default-sized pool that requires architecture remapping. */
-#define SWIOTLB_INIT_REMAP		(1 << 3)
+#define SWIOTLB_INIT_REMAP		(1 << 2)
 /* Do not initialize a pool unless SWIOTLB is explicitly required. */
-#define SWIOTLB_INIT_DEFAULT_OFF		(1 << 4)
+#define SWIOTLB_INIT_DEFAULT_OFF	(1 << 3)
 
 /*
  * Maximum allowable number of contiguous slabs to map,
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 130a13eb85b0..4d13421c3901 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -437,15 +437,10 @@ static void __init *swiotlb_memblock_alloc(unsigned long nslabs,
 	size_t bytes = PAGE_ALIGN(nslabs << IO_TLB_SHIFT);
 	void *tlb;
 
-	/*
-	 * By default allocate the bounce buffer memory from low memory, but
-	 * allow to pick a location everywhere for hypervisors with guest
-	 * memory encryption.
-	 */
-	if (flags & SWIOTLB_ANY)
-		tlb = memblock_alloc(bytes, PAGE_SIZE);
-	else
+	if (flags & SWIOTLB_INIT_ADDRESSING_LIMIT)
 		tlb = memblock_alloc_low(bytes, PAGE_SIZE);
+	else
+		tlb = memblock_alloc(bytes, PAGE_SIZE);
 
 	if (!tlb) {
 		pr_warn("%s: Failed to allocate %zu bytes tlb structure\n",
@@ -567,10 +562,10 @@ void __init swiotlb_init_remap(unsigned int flags,
 #ifdef CONFIG_SWIOTLB_DYNAMIC
 	if (!remap)
 		io_tlb_default_mem.can_grow = true;
-	if (flags & SWIOTLB_ANY)
-		io_tlb_default_mem.phys_limit = virt_to_phys(high_memory - 1);
-	else
+	if (flags & SWIOTLB_INIT_ADDRESSING_LIMIT)
 		io_tlb_default_mem.phys_limit = ARCH_LOW_ADDRESS_LIMIT;
+	else
+		io_tlb_default_mem.phys_limit = virt_to_phys(high_memory - 1);
 #endif
 
 	/* if we have host or guest memory encryption */
-- 
2.43.0

Re: [PATCH v6 0/8] dma: swiotlb: Centralize default pool policy and sizing

[Marek Szyprowski]

On 24.09.2026 08:07, Aneesh Kumar K.V (Arm) wrote:
> This series centralizes swiotlb default-pool selection and sizing, and
> simplifies the initialization flags used to describe pool placement.
>
> The first patch replaces the addressing-limit argument with initialization
> flags and introduces explicit policies for the different reasons a default
> pool may be needed. Architectures now report DMA addressing constraints with
> SWIOTLB_INIT_ADDRESSING_LIMIT, while the core selects the corresponding pool
> policy.
>
> The second patch moves the reduced sizing used when the pool is needed only
> for unaligned kmalloc bouncing from arm64 and RISC-V into the swiotlb core.
>
> The third patch centralizes swiotlb sizing for memory-encrypted systems. It
> moves the existing x86 guest-sizing policy into the core. Host memory
> encryption retains the normal pool size, and a shared default pool is not
> selected solely for guest memory encryption when a restricted DMA pool is
> present.
>
> The fourth patch removes SWIOTLB_ANY. Pool placement is derived directly from
> SWIOTLB_INIT_ADDRESSING_LIMIT: pools required for limited DMA addressing are
> allocated below the architecture's low address limit, while other pools may
> be allocated anywhere in directly mapped memory. Xen continues to request a
> pool explicitly with SWIOTLB_INIT_REMAP without imposing a low-address
> constraint.


I would like to give this patchset some tests in linux-next and merge this to
v7.4-rc1, as this is important continuation of the code already merged to v7.3.


Any chance to get some more acks from arch maintainers (especially x86)?
Unfortunately I had to reduce the CC list due to my smtp limits...

> ...
>
>  Documentation/core-api/swiotlb.rst   |   8 +-
>  arch/arm/mm/init.c                   |   6 +-
>  arch/arm/xen/mm.c                    |   2 +-
>  arch/arm64/mm/init.c                 |  14 +-
>  arch/loongarch/kernel/setup.c        |   2 +-
>  arch/mips/cavium-octeon/dma-octeon.c |   2 +-
>  arch/mips/loongson64/dma.c           |   2 +-
>  arch/mips/sibyte/common/dma.c        |   2 +-
>  arch/powerpc/kernel/dma-swiotlb.c    |   4 +-
>  arch/powerpc/mm/mem.c                |  17 ++-
>  arch/powerpc/platforms/pseries/svm.c |  10 --
>  arch/powerpc/sysdev/fsl_pci.c        |   1 +
>  arch/riscv/mm/init.c                 |  24 +---
>  arch/s390/mm/init.c                  |   2 +-
>  arch/x86/include/asm/crash_reserve.h |   4 +-
>  arch/x86/kernel/pci-dma.c            |  23 +++-
>  arch/x86/mm/mem_encrypt.c            |  24 ----
>  include/linux/swiotlb.h              |  17 ++-
>  kernel/dma/swiotlb.c                 | 193 +++++++++++++++++++--------
>  19 files changed, 210 insertions(+), 147 deletions(-)

Best regards

-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland