iommu/arm-smmu-v3: Ensure queue is read after updating prod pointer

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Reading the 'prod' MMIO register in order to determine whether or not
there is valid data beyond 'cons' for a given queue does not provide
sufficient dependency ordering, as the resulting access is address
dependent only on 'cons' and can therefore be speculated ahead of time,
potentially allowing stale data to be read by the CPU.

Use readl() instead of readl_relaxed() when updating the shadow copy of
the 'prod' pointer, so that all speculated memory reads from the
corresponding queue can occur only from valid slots.

Signed-off-by: Zhou Wang <wangzhou1@hisilicon.com>
Link: https://lore.kernel.org/r/1601281922-117296-1-git-send-email-wangzhou1@hisilicon.com
[will: Use readl() instead of explicit barrier. Update 'cons' side to match.]
Signed-off-by: Will Deacon <will@kernel.org>

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Zhou Wang 2020-09-28 16:32:02 +08:00 • committed by Will Deacon

parent 1226fa0e54

commit a76a37777f

3 changed files with 11 additions and 2 deletions

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1

arch/arm64/include/asm/barrier.h

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1

arch/arm64/include/asm/io.h

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11

drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c

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