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

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Message-ID: <CAMC_AXXgBoRZOaDpCex+g_YeOdPQpKD3moQ8VMsqVEm2nqSrjg@mail.gmail.com>
Date:   Tue, 16 May 2023 13:59:16 -0700
From:   Jon Pan-Doh <pandoh@...gle.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        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>, stable@...r.kernel.org
Subject: Re: [PATCH] iommu/amd: Fix domain flush size when syncing iotlb

Hi Joerg,

[Cc'ing stable@...r.kernel.org per Nadav's suggestion]

This bug fix seems to have gotten the necessary reviews (AMD and
previous commit author). Is it eligible to be applied?

Thanks,
Jon

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>
> ---
>  drivers/iommu/amd/iommu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> index 5a505ba5467e..da45b1ab042d 100644
> --- a/drivers/iommu/amd/iommu.c
> +++ b/drivers/iommu/amd/iommu.c
> @@ -2378,7 +2378,7 @@ static void amd_iommu_iotlb_sync(struct iommu_domain *domain,
>         unsigned long flags;
>
>         spin_lock_irqsave(&dom->lock, flags);
> -       domain_flush_pages(dom, gather->start, gather->end - gather->start, 1);
> +       domain_flush_pages(dom, gather->start, gather->end - gather->start + 1, 1);
>         amd_iommu_domain_flush_complete(dom);
>         spin_unlock_irqrestore(&dom->lock, flags);
>  }
> --
> 2.40.0.634.g4ca3ef3211-goog
>