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iommu/arm-smmu-v3: Avoid memory corruption from Hisilicon MSI payloads

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The GITS_TRANSLATER MMIO doorbell register in the ITS hardware is
architected to be 4 bytes in size, yet on hi1620 and earlier, Hisilicon
have allocated the adjacent 4 bytes to carry some IMPDEF sideband
information which results in an 8-byte MSI payload being delivered when
signalling an interrupt:

MSIAddr:
	 |----4bytes----|----4bytes----|
	 |    MSIData   |    IMPDEF    |

This poses no problem for the ITS hardware because the adjacent 4 bytes
are reserved in the memory map. However, when delivering MSIs to memory,
as we do in the SMMUv3 driver for signalling the completion of a SYNC
command, the extended payload will corrupt the 4 bytes adjacent to the
"sync_count" member in struct arm_smmu_device. Fortunately, the current
layout allocates these bytes to padding, but this is fragile and we
should make this explicit.

Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
[will: Rewrote commit message and comment]
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Zhen Lei 2018-10-31 12:02:07 +08:00 committed by Will Deacon
parent 3cd508a8c1
commit 84a9a75774
1 changed files with 5 additions and 1 deletions
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6
drivers/iommu/arm-smmu-v3.c
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@ -576,7 +576,11 @@ struct arm_smmu_device {
struct arm_smmu_strtab_cfg strtab_cfg;
u32 sync_count;
/* Hi16xx adds an extra 32 bits of goodness to its MSI payload */
union {
u32 sync_count;
u64 padding;
};
/* IOMMU core code handle */
struct iommu_device iommu;