[PATCH 0/2] arm64: retry dropping HAVE_ARCH_PFN_VALID

From: Mike Rapoport <redacted>

Hi,

This is a new attempt to drop HAVE_ARCH_PFN_VALID on arm64 and start using
the generic implementation of pfn_valid().

The first patch removes the check for pfn_valid() in dma_map_resource()
which is required to avoid false positives when there is memory map for
MMIO.

Anshuman Khandual (1):
  arm64/mm: drop HAVE_ARCH_PFN_VALID

Mike Rapoport (1):
  dma-mapping: remove bogus test for pfn_valid from dma_map_resource

 arch/arm64/Kconfig            |  1 -
 arch/arm64/include/asm/page.h |  1 -
 arch/arm64/mm/init.c          | 37 -----------------------------------
 kernel/dma/mapping.c          |  4 ----
 4 files changed, 43 deletions(-)


base-commit: 5816b3e6577eaa676ceb00a848f0fd65fe2adc29
-- 
2.28.0


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From: Mike Rapoport <redacted>

dma_map_resource() uses pfn_valid() to ensure the range is not RAM.
However, pfn_valid() only checks for availability of the memory map for a
PFN but it does not ensure that the PFN is actually backed by RAM.

As dma_map_resource() is the only method in DMA mapping APIs that has this
check, simply drop the pfn_valid() test from dma_map_resource().

Link: https://lore.kernel.org/all/20210824173741.GC623@arm.com/
Signed-off-by: Mike Rapoport <redacted>
---
 kernel/dma/mapping.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 06fec5547e7c..dda8d8b84a55 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c

@@ -296,10 +296,6 @@ dma_addr_t dma_map_resource(struct device *dev, phys_addr_t phys_addr,
 	if (WARN_ON_ONCE(!dev->dma_mask))
 		return DMA_MAPPING_ERROR;
 
-	/* Don't allow RAM to be mapped */
-	if (WARN_ON_ONCE(pfn_valid(PHYS_PFN(phys_addr))))
-		return DMA_MAPPING_ERROR;
-
 	if (dma_map_direct(dev, ops))
 		addr = dma_direct_map_resource(dev, phys_addr, size, dir, attrs);
 	else if (ops->map_resource)

-- 
2.28.0


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From: Anshuman Khandual <redacted>

CONFIG_SPARSEMEM_VMEMMAP is now the only available memory model on arm64
platforms and free_unused_memmap() would just return without creating any
holes in the memmap mapping.  There is no need for any special handling in
pfn_valid() and HAVE_ARCH_PFN_VALID can just be dropped.  This also moves
the pfn upper bits sanity check into generic pfn_valid().

[rppt: rebased on v5.15-rc3]

Link: https://lkml.kernel.org/r/1621947349-25421-1-git-send-email-anshuman.khandual@arm.com
Signed-off-by: Anshuman Khandual <redacted>
Acked-by: David Hildenbrand <redacted>
Acked-by: Mike Rapoport <redacted>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: David Hildenbrand <redacted>
Cc: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mike Rapoport <redacted>
---
 arch/arm64/Kconfig            |  1 -
 arch/arm64/include/asm/page.h |  1 -
 arch/arm64/mm/init.c          | 37 -----------------------------------
 3 files changed, 39 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 5c7ae4c3954b..53dd23f305be 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig

@@ -154,7 +154,6 @@ config ARM64
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_MMAP_RND_BITS
 	select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
-	select HAVE_ARCH_PFN_VALID
 	select HAVE_ARCH_PREL32_RELOCATIONS
 	select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
 	select HAVE_ARCH_SECCOMP_FILTER

diff --git a/arch/arm64/include/asm/page.h b/arch/arm64/include/asm/page.h
index f98c91bbd7c1..993a27ea6f54 100644
--- a/arch/arm64/include/asm/page.h
+++ b/arch/arm64/include/asm/page.h

@@ -41,7 +41,6 @@ void tag_clear_highpage(struct page *to);
 
 typedef struct page *pgtable_t;
 
-int pfn_valid(unsigned long pfn);
 int pfn_is_map_memory(unsigned long pfn);
 
 #include <asm/memory.h>

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 37a81754d9b6..e60c6eb813b7 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c

@@ -160,43 +160,6 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
 	free_area_init(max_zone_pfns);
 }
 
-int pfn_valid(unsigned long pfn)
-{
-	phys_addr_t addr = PFN_PHYS(pfn);
-	struct mem_section *ms;
-
-	/*
-	 * Ensure the upper PAGE_SHIFT bits are clear in the
-	 * pfn. Else it might lead to false positives when
-	 * some of the upper bits are set, but the lower bits
-	 * match a valid pfn.
-	 */
-	if (PHYS_PFN(addr) != pfn)
-		return 0;
-
-	if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
-		return 0;
-
-	ms = __pfn_to_section(pfn);
-	if (!valid_section(ms))
-		return 0;
-
-	/*
-	 * ZONE_DEVICE memory does not have the memblock entries.
-	 * memblock_is_map_memory() check for ZONE_DEVICE based
-	 * addresses will always fail. Even the normal hotplugged
-	 * memory will never have MEMBLOCK_NOMAP flag set in their
-	 * memblock entries. Skip memblock search for all non early
-	 * memory sections covering all of hotplug memory including
-	 * both normal and ZONE_DEVICE based.
-	 */
-	if (!early_section(ms))
-		return pfn_section_valid(ms, pfn);
-
-	return memblock_is_memory(addr);
-}
-EXPORT_SYMBOL(pfn_valid);
-
 int pfn_is_map_memory(unsigned long pfn)
 {
 	phys_addr_t addr = PFN_PHYS(pfn);

-- 
2.28.0


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On Thu, Sep 30, 2021 at 04:30:38AM +0300, Mike Rapoport wrote:

From: Mike Rapoport <redacted>

dma_map_resource() uses pfn_valid() to ensure the range is not RAM.
However, pfn_valid() only checks for availability of the memory map for a
PFN but it does not ensure that the PFN is actually backed by RAM.

As dma_map_resource() is the only method in DMA mapping APIs that has this
check, simply drop the pfn_valid() test from dma_map_resource().

Link: https://lore.kernel.org/all/20210824173741.GC623@arm.com/
Signed-off-by: Mike Rapoport <redacted>

We'll lose a bit of a sanity check with this, but given the problems it
caused:

Reviewed-by: Christoph Hellwig <hch@lst.de>

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On 30.09.21 03:30, Mike Rapoport wrote:

From: Mike Rapoport <redacted>

dma_map_resource() uses pfn_valid() to ensure the range is not RAM.
However, pfn_valid() only checks for availability of the memory map for a
PFN but it does not ensure that the PFN is actually backed by RAM.

As dma_map_resource() is the only method in DMA mapping APIs that has this
check, simply drop the pfn_valid() test from dma_map_resource().

Link: https://lore.kernel.org/all/20210824173741.GC623@arm.com/
Signed-off-by: Mike Rapoport <redacted>
---

Acked-by: David Hildenbrand <redacted>

-- 
Thanks,

David / dhildenb


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On Thu, 30 Sep 2021 04:30:37 +0300, Mike Rapoport wrote:

From: Mike Rapoport <redacted>

Hi,

This is a new attempt to drop HAVE_ARCH_PFN_VALID on arm64 and start using
the generic implementation of pfn_valid().

[...]

Applied to arm64 (for-next/pfn-valid), thanks!

[1/2] dma-mapping: remove bogus test for pfn_valid from dma_map_resource
      https://git.kernel.org/arm64/c/a9c38c5d267c
[2/2] arm64/mm: drop HAVE_ARCH_PFN_VALID
      https://git.kernel.org/arm64/c/3de360c3fdb3

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev

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