linux-kernel - Re: [PATCH] iommu/amd: Fix domain flush size when syncing iotlb

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Date:   Tue, 16 May 2023 22:49:13 -0700
From:   Jon Pan-Doh <pandoh@...gle.com>
To:     Joerg Roedel <joro@...tes.org>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Cc:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Nadav Amit <namit@...are.com>, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org,
        Sudheer Dantuluri <dantuluris@...gle.com>,
        Gary Zibrat <gzibrat@...gle.com>
Subject: Re: [PATCH] iommu/amd: Fix domain flush size when syncing iotlb

On Wed, Apr 26, 2023 at 1:32 PM Jon Pan-Doh <pandoh@...gle.com> wrote:
>
> When running on an AMD vIOMMU, we observed multiple invalidations (of
> decreasing power of 2 aligned sizes) when unmapping a single page.
>
> Domain flush takes gather bounds (end-start) as size param. However,
> gather->end is defined as the last inclusive address (start + size - 1).
> This leads to an off by 1 error.
>
> With this patch, verified that 1 invalidation occurs when unmapping a
> single page.
>
> Fixes: a270be1b3fdf ("iommu/amd: Use only natural aligned flushes in a VM")
> Signed-off-by: Jon Pan-Doh <pandoh@...gle.com>
> Tested-by: Sudheer Dantuluri <dantuluris@...gle.com>
> Suggested-by: Gary Zibrat <gzibrat@...gle.com>

Cc: stable@...r.kernel.org