[PATCH 0/2] x86/mm: Make memremap(MEMREMAP_WB) map memory as encrypted by default

[PATCH 0/2] x86/mm: Make memremap(MEMREMAP_WB) map memory as encrypted by default

[Kirill A. Shutemov]

Make memremap(MEMREMAP_WB) produce encrypted/private mapping by default
unless MEMREMAP_DEC is specified.

It fixes crash on kexec in TDX guests if CONFIG_EISA is enabled.

Kirill A. Shutemov (2):
  memremap: Pass down MEMREMAP_* flags to arch_memremap_wb()
  x86/mm: Make memremap(MEMREMAP_WB) map memory as encrypted by default

 arch/arm/include/asm/io.h   | 2 +-
 arch/arm/mm/ioremap.c       | 2 +-
 arch/arm/mm/nommu.c         | 2 +-
 arch/riscv/include/asm/io.h | 2 +-
 arch/x86/include/asm/io.h   | 3 +++
 arch/x86/mm/ioremap.c       | 8 ++++++++
 kernel/iomem.c              | 5 +++--
 7 files changed, 18 insertions(+), 6 deletions(-)

-- 
2.45.2

[PATCH 1/2] memremap: Pass down MEMREMAP_* flags to arch_memremap_wb()

[Kirill A. Shutemov]

x86 version of arch_memremap_wb() needs the flags to decide if the mapping
has be encrypted or decrypted.

Pass down the flag to arch_memremap_wb(). All current implementations
ignore the argument.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/arm/include/asm/io.h   | 2 +-
 arch/arm/mm/ioremap.c       | 2 +-
 arch/arm/mm/nommu.c         | 2 +-
 arch/riscv/include/asm/io.h | 2 +-
 kernel/iomem.c              | 5 +++--
 5 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h
index 1815748f5d2a..bae5edf348ef 100644
--- a/arch/arm/include/asm/io.h
+++ b/arch/arm/include/asm/io.h
@@ -381,7 +381,7 @@ void __iomem *ioremap_wc(resource_size_t res_cookie, size_t size);
 void iounmap(volatile void __iomem *io_addr);
 #define iounmap iounmap
 
-void *arch_memremap_wb(phys_addr_t phys_addr, size_t size);
+void *arch_memremap_wb(phys_addr_t phys_addr, size_t size, unsigned long flags);
 #define arch_memremap_wb arch_memremap_wb
 
 /*
diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c
index 794cfea9f9d4..9f7883e6db46 100644
--- a/arch/arm/mm/ioremap.c
+++ b/arch/arm/mm/ioremap.c
@@ -411,7 +411,7 @@ void __arm_iomem_set_ro(void __iomem *ptr, size_t size)
 	set_memory_ro((unsigned long)ptr, PAGE_ALIGN(size) / PAGE_SIZE);
 }
 
-void *arch_memremap_wb(phys_addr_t phys_addr, size_t size)
+void *arch_memremap_wb(phys_addr_t phys_addr, size_t size, unsigned long flags)
 {
 	return (__force void *)arch_ioremap_caller(phys_addr, size,
 						   MT_MEMORY_RW,
diff --git a/arch/arm/mm/nommu.c b/arch/arm/mm/nommu.c
index c415f3859b20..279641f0780e 100644
--- a/arch/arm/mm/nommu.c
+++ b/arch/arm/mm/nommu.c
@@ -251,7 +251,7 @@ void __iomem *pci_remap_cfgspace(resource_size_t res_cookie, size_t size)
 EXPORT_SYMBOL_GPL(pci_remap_cfgspace);
 #endif
 
-void *arch_memremap_wb(phys_addr_t phys_addr, size_t size)
+void *arch_memremap_wb(phys_addr_t phys_addr, size_t size, unsigned long flags)
 {
 	return (void *)phys_addr;
 }
diff --git a/arch/riscv/include/asm/io.h b/arch/riscv/include/asm/io.h
index 1c5c641075d2..0257f4aa7ff4 100644
--- a/arch/riscv/include/asm/io.h
+++ b/arch/riscv/include/asm/io.h
@@ -136,7 +136,7 @@ __io_writes_outs(outs, u64, q, __io_pbr(), __io_paw())
 #include <asm-generic/io.h>
 
 #ifdef CONFIG_MMU
-#define arch_memremap_wb(addr, size)	\
+#define arch_memremap_wb(addr, size, flags)	\
 	((__force void *)ioremap_prot((addr), (size), _PAGE_KERNEL))
 #endif
 
diff --git a/kernel/iomem.c b/kernel/iomem.c
index dc2120776e1c..75e61c1c6bc0 100644
--- a/kernel/iomem.c
+++ b/kernel/iomem.c
@@ -6,7 +6,8 @@
 #include <linux/ioremap.h>
 
 #ifndef arch_memremap_wb
-static void *arch_memremap_wb(resource_size_t offset, unsigned long size)
+static void *arch_memremap_wb(resource_size_t offset, unsigned long size,
+			      unsigned long flags)
 {
 #ifdef ioremap_cache
 	return (__force void *)ioremap_cache(offset, size);
@@ -91,7 +92,7 @@ void *memremap(resource_size_t offset, size_t size, unsigned long flags)
 		if (is_ram == REGION_INTERSECTS)
 			addr = try_ram_remap(offset, size, flags);
 		if (!addr)
-			addr = arch_memremap_wb(offset, size);
+			addr = arch_memremap_wb(offset, size, flags);
 	}
 
 	/*
-- 
2.45.2

[PATCH 2/2] x86/mm: Make memremap(MEMREMAP_WB) map memory as encrypted by default

[Kirill A. Shutemov]

Currently memremap(MEMREMAP_WB) produces decrypted/shared mapping:

memremap(MEMREMAP_WB)
  arch_memremap_wb()
    ioremap_cache()
      __ioremap_caller(.encrytped = false)

It is a bad default. On TDX guests, access via shared mapping can be
destructive[1].

Kernel already provides a way to request decrypted mapping explicitly
via MEMREMAP_DEC flag.

Make memremap(MEMREMAP_WB) produce encrypted/private mapping by default
unless MEMREMAP_DEC is specified.

It fixes crash on kexec in TDX guests if CONFIG_EISA is enabled.

[1] https://lore.kernel.org/all/20240822095122.736522-1-kirill.shutemov@linux.intel.com

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: "Maciej W. Rozycki" <macro@orcam.me.uk>
---
 arch/x86/include/asm/io.h | 3 +++
 arch/x86/mm/ioremap.c     | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index 1d60427379c9..1a3a34b40598 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -180,6 +180,9 @@ extern void __iomem *ioremap_prot(resource_size_t offset, unsigned long size, un
 extern void __iomem *ioremap_encrypted(resource_size_t phys_addr, unsigned long size);
 #define ioremap_encrypted ioremap_encrypted
 
+void *arch_memremap_wb(phys_addr_t phys_addr, size_t size, unsigned long flags);
+#define arch_memremap_wb arch_memremap_wb
+
 /**
  * ioremap     -   map bus memory into CPU space
  * @offset:    bus address of the memory
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 70b02fc61d93..fc65a81fd777 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -503,6 +503,14 @@ void iounmap(volatile void __iomem *addr)
 }
 EXPORT_SYMBOL(iounmap);
 
+void *arch_memremap_wb(phys_addr_t phys_addr, size_t size, unsigned long flags)
+{
+	if (flags & MEMREMAP_DEC)
+		return ioremap_cache(phys_addr, size);
+
+	return ioremap_encrypted(phys_addr, size);
+}
+
 /*
  * Convert a physical pointer to a virtual kernel pointer for /dev/mem
  * access
-- 
2.45.2

Re: [PATCH 2/2] x86/mm: Make memremap(MEMREMAP_WB) map memory as encrypted by default

[kernel test robot]

Hi Kirill,

kernel test robot noticed the following build warnings:

[auto build test WARNING on tip/master]
[also build test WARNING on tip/x86/mm linus/master tip/auto-latest tip/x86/core v6.12-rc3 next-20241018]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Kirill-A-Shutemov/memremap-Pass-down-MEMREMAP_-flags-to-arch_memremap_wb/20241018-001138
base:   tip/master
patch link:    https://lore.kernel.org/r/20241017155642.1942514-3-kirill.shutemov%40linux.intel.com
patch subject: [PATCH 2/2] x86/mm: Make memremap(MEMREMAP_WB) map memory as encrypted by default
config: i386-randconfig-061-20241019 (https://download.01.org/0day-ci/archive/20241020/202410200112.Ut6HtXKD-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241020/202410200112.Ut6HtXKD-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202410200112.Ut6HtXKD-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> arch/x86/mm/ioremap.c:509:37: sparse: sparse: incorrect type in return expression (different address spaces) @@     expected void * @@     got void [noderef] __iomem * @@
   arch/x86/mm/ioremap.c:509:37: sparse:     expected void *
   arch/x86/mm/ioremap.c:509:37: sparse:     got void [noderef] __iomem *
   arch/x86/mm/ioremap.c:511:33: sparse: sparse: incorrect type in return expression (different address spaces) @@     expected void * @@     got void [noderef] __iomem * @@
   arch/x86/mm/ioremap.c:511:33: sparse:     expected void *
   arch/x86/mm/ioremap.c:511:33: sparse:     got void [noderef] __iomem *

vim +509 arch/x86/mm/ioremap.c

   505	
   506	void *arch_memremap_wb(phys_addr_t phys_addr, size_t size, unsigned long flags)
   507	{
   508		if (flags & MEMREMAP_DEC)
 > 509			return ioremap_cache(phys_addr, size);
   510	
   511		return ioremap_encrypted(phys_addr, size);
   512	}
   513	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki