4.20-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 84a9a75774961612d0c7dd34a1777e8f98a65abd ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/iommu/arm-smmu-v3.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index 71eda422c926..62ef4afc9ee5 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c @@ -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;