[PATCH 1/1] iommu/arm-smmu-v3: eliminate a potential memory corruption on Hi16xx soc
From: Andrew Murray <hidden>
Date: 2018-10-16 09:48:52
Also in:
linux-iommu, lkml
Hi Zhen, On Mon, Oct 15, 2018 at 04:36:16PM +0800, Zhen Lei wrote:
ITS translation register map: 0x0000-0x003C Reserved 0x0040 GITS_TRANSLATER 0x0044-0xFFFC Reserved The standard GITS_TRANSLATER register in ITS is only 4 bytes, but Hisilicon expands the next 4 bytes to carry some IMPDEF information. That means, 8 bytes data will be written to MSIAddress each time. MSIAddr: |----4bytes----|----4bytes----| | MSIData | IMPDEF | There is no problem for ITS, because the next 4 bytes space is reserved in ITS. But it will overwrite the 4 bytes memory following "sync_count". It's very luckly that the previous and the next neighbour of "sync_count" are both aligned by 8 bytes, so no problem is met now.
My understanding is that MSI's are 32bit memory writes and as such the SMMU performs a 32bit write in response to the MSI. If so then what is different with the Hi16xx that causes a problem? Have you been able to able to adjust the layout of the arm_smmu_device struct to demonstrate this? Thanks, Andrew Murray
quoted hunk ↗ jump to hunk
It's good to explicitly add a workaround: 1. Add gcc __attribute__((aligned(8))) to make sure that "sync_count" is always aligned by 8 bytes. 2. Add a "u64" union member to make sure the 4 bytes padding is always exist. There is no functional change. Signed-off-by: Zhen Lei <redacted> --- drivers/iommu/arm-smmu-v3.c | 3 +++ 1 file changed, 3 insertions(+)diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index 5059d09..a07bc0d 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c@@ -586,7 +586,10 @@ struct arm_smmu_device { struct arm_smmu_strtab_cfg strtab_cfg; + union { + u64 padding; /* workaround for Hisilicon */ u32 sync_count; + } __attribute__((aligned(8))); /* IOMMU core code handle */ struct iommu_device iommu;-- 1.8.3 _______________________________________________ iommu mailing list iommu at lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu