linux-kernel - Re: [PATCH v3] iommu/vt-d: Add a fix for devices need extra dtlb flush

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Message-ID: <c58ff308-f53f-ce3e-aace-2aec2e6e72c1@linux.intel.com>
Date:   Thu, 1 Dec 2022 12:02:50 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>, iommu@...ts.linux.dev,
        Joerg Roedel <joro@...tes.org>
Cc:     baolu.lu@...ux.intel.com, Robin Murphy <robin.murphy@....com>,
        Will Deacon <will@...nel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Raj Ashok <ashok.raj@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        Yuzhang Luo <yuzhang.luo@...el.com>
Subject: Re: [PATCH v3] iommu/vt-d: Add a fix for devices need extra dtlb
 flush

On 2022/11/30 14:24, Jacob Pan wrote:
> QAT devices on Intel Sapphire Rapids and Emerald Rapids have a defect in
> address translation service (ATS). These devices may inadvertently issue
> ATS invalidation completion before posted writes initiated with
> translated address that utilized translations matching the invalidation
> address range, violating the invalidation completion ordering.
> 
> This patch adds an extra device TLB invalidation for the affected devices,
> it is needed to ensure no more posted writes with translated address
> following the invalidation completion. Therefore, the ordering is
> preserved and data-corruption is prevented.
> 
> Device TLBs are invalidated under the following six conditions:
> 1. Device driver does DMA API unmap IOVA
> 2. Device driver unbind a PASID from a process, sva_unbind_device()
> 3. PASID is torn down, after PASID cache is flushed. e.g. process
> exit_mmap() due to crash
> 4. Under SVA usage, called by mmu_notifier.invalidate_range() where
> VM has to free pages that were unmapped
> 5. userspace driver unmaps a DMA buffer
> 6. Cache invalidation in vSVA usage (upcoming)
> 
> For #1 and #2, device drivers are responsible for stopping DMA traffic
> before unmap/unbind. For #3, iommu driver gets mmu_notifier to
> invalidate TLB the same way as normal user unmap which will do an extra
> invalidation. The dTLB invalidation after PASID cache flush does not
> need an extra invalidation.
> 
> Therefore, we only need to deal with #4 and #5 in this patch. #1 is also
> covered by this patch due to common code path with #5.
> 
> Tested-by: Yuzhang Luo<yuzhang.luo@...el.com>
> Reviewed-by: Ashok Raj<ashok.raj@...el.com>
> Reviewed-by: Kevin Tian<kevin.tian@...el.com>
> Signed-off-by: Jacob Pan<jacob.jun.pan@...ux.intel.com>

Queued for Joerg. Thank you!

Best regards,
baolu