[PATCH 0/2] xtensa: cache aliasing fixes

[PATCH 0/2] xtensa: cache aliasing fixes

[Max Filippov]

Hello,

this series changes TLBTEMP region placement and disables preemption
around all cache alias management calls. This fixes TLB miss and
multihit issues in the TLBTEMP area seen on cores with aliasing cache.

Max Filippov (2):
  xtensa: fix TLBTEMP area placement
  xtensa: disable preemption around cache alias management calls

 Documentation/xtensa/mmu.rst      |  9 ++++++---
 arch/xtensa/include/asm/pgtable.h |  2 +-
 arch/xtensa/mm/cache.c            | 14 ++++++++++++++
 3 files changed, 21 insertions(+), 4 deletions(-)

-- 
2.20.1

[PATCH 1/2] xtensa: fix TLBTEMP area placement

[Max Filippov]

fast_second_level_miss handler for the TLBTEMP area has an assumption
that page table directory entry for the TLBTEMP address range is 0. For
it to be true the TLBTEMP area must be aligned to 4MB boundary and not
share its 4MB region with anything that may use a page table. This is
not true currently: TLBTEMP shares space with vmalloc space which
results in the following kinds of runtime errors when
fast_second_level_miss loads page table directory entry for the vmalloc
space instead of fixing up the TLBTEMP area:

 Unable to handle kernel paging request at virtual address c7ff0e00
  pc = d0009275, ra = 90009478
 Oops: sig: 9 [#1] PREEMPT
 CPU: 1 PID: 61 Comm: kworker/u9:2 Not tainted 5.10.0-rc3-next-20201110-00007-g1fe4962fa983-dirty #58
 Workqueue: xprtiod xs_stream_data_receive_workfn
 a00: 90009478 d11e1dc0 c7ff0e00 00000020 c7ff0000 00000001 7f8b8107 00000000
 a08: 900c5992 d11e1d90 d0cc88b8 5506e97c 00000000 5506e97c d06c8074 d11e1d90
 pc: d0009275, ps: 00060310, depc: 00000014, excvaddr: c7ff0e00
 lbeg: d0009275, lend: d0009287 lcount: 00000003, sar: 00000010
 Call Trace:
   xs_stream_data_receive_workfn+0x43c/0x770
   process_one_work+0x1a1/0x324
   worker_thread+0x1cc/0x3c0
   kthread+0x10d/0x124
   ret_from_kernel_thread+0xc/0x18

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
 Documentation/xtensa/mmu.rst      | 9 ++++++---
 arch/xtensa/include/asm/pgtable.h | 2 +-
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/Documentation/xtensa/mmu.rst b/Documentation/xtensa/mmu.rst
index e52a12960fdc..450573afa31a 100644
--- a/Documentation/xtensa/mmu.rst
+++ b/Documentation/xtensa/mmu.rst
@@ -82,7 +82,8 @@ Default MMUv2-compatible layout::
   +------------------+
   | VMALLOC area     |  VMALLOC_START            0xc0000000  128MB - 64KB
   +------------------+  VMALLOC_END
-  | Cache aliasing   |  TLBTEMP_BASE_1           0xc7ff0000  DCACHE_WAY_SIZE
+  +------------------+
+  | Cache aliasing   |  TLBTEMP_BASE_1           0xc8000000  DCACHE_WAY_SIZE
   | remap area 1     |
   +------------------+
   | Cache aliasing   |  TLBTEMP_BASE_2                       DCACHE_WAY_SIZE
@@ -124,7 +125,8 @@ Default MMUv2-compatible layout::
   +------------------+
   | VMALLOC area     |  VMALLOC_START            0xa0000000  128MB - 64KB
   +------------------+  VMALLOC_END
-  | Cache aliasing   |  TLBTEMP_BASE_1           0xa7ff0000  DCACHE_WAY_SIZE
+  +------------------+
+  | Cache aliasing   |  TLBTEMP_BASE_1           0xa8000000  DCACHE_WAY_SIZE
   | remap area 1     |
   +------------------+
   | Cache aliasing   |  TLBTEMP_BASE_2                       DCACHE_WAY_SIZE
@@ -167,7 +169,8 @@ Default MMUv2-compatible layout::
   +------------------+
   | VMALLOC area     |  VMALLOC_START            0x90000000  128MB - 64KB
   +------------------+  VMALLOC_END
-  | Cache aliasing   |  TLBTEMP_BASE_1           0x97ff0000  DCACHE_WAY_SIZE
+  +------------------+
+  | Cache aliasing   |  TLBTEMP_BASE_1           0x98000000  DCACHE_WAY_SIZE
   | remap area 1     |
   +------------------+
   | Cache aliasing   |  TLBTEMP_BASE_2                       DCACHE_WAY_SIZE
diff --git a/arch/xtensa/include/asm/pgtable.h b/arch/xtensa/include/asm/pgtable.h
index fa054a1772e1..4dc04e6c01d7 100644
--- a/arch/xtensa/include/asm/pgtable.h
+++ b/arch/xtensa/include/asm/pgtable.h
@@ -69,7 +69,7 @@
  */
 #define VMALLOC_START		(XCHAL_KSEG_CACHED_VADDR - 0x10000000)
 #define VMALLOC_END		(VMALLOC_START + 0x07FEFFFF)
-#define TLBTEMP_BASE_1		(VMALLOC_END + 1)
+#define TLBTEMP_BASE_1		(VMALLOC_START + 0x08000000)
 #define TLBTEMP_BASE_2		(TLBTEMP_BASE_1 + DCACHE_WAY_SIZE)
 #if 2 * DCACHE_WAY_SIZE > ICACHE_WAY_SIZE
 #define TLBTEMP_SIZE		(2 * DCACHE_WAY_SIZE)
-- 
2.20.1

[PATCH 2/2] xtensa: disable preemption around cache alias management calls

[Max Filippov]

Although cache alias management calls set up and tear down TLB entries
and fast_second_level_miss is able to restore TLB entry should it be
evicted they absolutely cannot preempt each other because they use the
same TLBTEMP area for different purposes.
Disable preemption around all cache alias management calls to enforce
that.

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
 arch/xtensa/mm/cache.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/xtensa/mm/cache.c b/arch/xtensa/mm/cache.c
index 5835406b3cec..085b8c77b9d9 100644
--- a/arch/xtensa/mm/cache.c
+++ b/arch/xtensa/mm/cache.c
@@ -70,8 +70,10 @@ static inline void kmap_invalidate_coherent(struct page *page,
 			kvaddr = TLBTEMP_BASE_1 +
 				(page_to_phys(page) & DCACHE_ALIAS_MASK);
 
+			preempt_disable();
 			__invalidate_dcache_page_alias(kvaddr,
 						       page_to_phys(page));
+			preempt_enable();
 		}
 	}
 }
@@ -156,6 +158,7 @@ void flush_dcache_page(struct page *page)
 		if (!alias && !mapping)
 			return;
 
+		preempt_disable();
 		virt = TLBTEMP_BASE_1 + (phys & DCACHE_ALIAS_MASK);
 		__flush_invalidate_dcache_page_alias(virt, phys);
 
@@ -166,6 +169,7 @@ void flush_dcache_page(struct page *page)
 
 		if (mapping)
 			__invalidate_icache_page_alias(virt, phys);
+		preempt_enable();
 	}
 
 	/* There shouldn't be an entry in the cache for this page anymore. */
@@ -199,8 +203,10 @@ void local_flush_cache_page(struct vm_area_struct *vma, unsigned long address,
 	unsigned long phys = page_to_phys(pfn_to_page(pfn));
 	unsigned long virt = TLBTEMP_BASE_1 + (address & DCACHE_ALIAS_MASK);
 
+	preempt_disable();
 	__flush_invalidate_dcache_page_alias(virt, phys);
 	__invalidate_icache_page_alias(virt, phys);
+	preempt_enable();
 }
 EXPORT_SYMBOL(local_flush_cache_page);
 
@@ -227,11 +233,13 @@ update_mmu_cache(struct vm_area_struct * vma, unsigned long addr, pte_t *ptep)
 		unsigned long phys = page_to_phys(page);
 		unsigned long tmp;
 
+		preempt_disable();
 		tmp = TLBTEMP_BASE_1 + (phys & DCACHE_ALIAS_MASK);
 		__flush_invalidate_dcache_page_alias(tmp, phys);
 		tmp = TLBTEMP_BASE_1 + (addr & DCACHE_ALIAS_MASK);
 		__flush_invalidate_dcache_page_alias(tmp, phys);
 		__invalidate_icache_page_alias(tmp, phys);
+		preempt_enable();
 
 		clear_bit(PG_arch_1, &page->flags);
 	}
@@ -265,7 +273,9 @@ void copy_to_user_page(struct vm_area_struct *vma, struct page *page,
 
 	if (alias) {
 		unsigned long t = TLBTEMP_BASE_1 + (vaddr & DCACHE_ALIAS_MASK);
+		preempt_disable();
 		__flush_invalidate_dcache_page_alias(t, phys);
+		preempt_enable();
 	}
 
 	/* Copy data */
@@ -280,9 +290,11 @@ void copy_to_user_page(struct vm_area_struct *vma, struct page *page,
 	if (alias) {
 		unsigned long t = TLBTEMP_BASE_1 + (vaddr & DCACHE_ALIAS_MASK);
 
+		preempt_disable();
 		__flush_invalidate_dcache_range((unsigned long) dst, len);
 		if ((vma->vm_flags & VM_EXEC) != 0)
 			__invalidate_icache_page_alias(t, phys);
+		preempt_enable();
 
 	} else if ((vma->vm_flags & VM_EXEC) != 0) {
 		__flush_dcache_range((unsigned long)dst,len);
@@ -304,7 +316,9 @@ extern void copy_from_user_page(struct vm_area_struct *vma, struct page *page,
 
 	if (alias) {
 		unsigned long t = TLBTEMP_BASE_1 + (vaddr & DCACHE_ALIAS_MASK);
+		preempt_disable();
 		__flush_invalidate_dcache_page_alias(t, phys);
+		preempt_enable();
 	}
 
 	memcpy(dst, src, len);
-- 
2.20.1