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

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Message-ID: <985C9735-6009-449B-BF9A-1293AFBCBDE7@vmware.com>
Date:   Wed, 26 Apr 2023 21:22:56 +0000
From:   Nadav Amit <namit@...are.com>
To:     Jon Pan-Doh <pandoh@...gle.com>
CC:     Joerg Roedel <joro@...tes.org>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <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 Apr 26, 2023, at 2:04 PM, Nadav Amit <namit@...are.com> wrote:
> 
> 
> 
>> On 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>
>> 
> 
> Sorry for that.
> 
> Acked-by: Nadav Amit <namit@...are.com>

P.S. I think it is stable-worthy.