linux-kernel - Re: [PATCH v7 7/8] vfio: Permit VFIO to work with pinned importers

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Message-Id: <1b7ee5ad-6dde-415a-8e06-93daddc9bcef@app.fastmail.com>
Date: Thu, 05 Feb 2026 07:41:11 -0700
From: "Alex Williamson" <alex@...zbot.org>
To: Christian König <christian.koenig@....com>,
 "Jason Gunthorpe" <jgg@...pe.ca>, "Leon Romanovsky" <leon@...nel.org>
Cc: "Simona Vetter" <simona@...ll.ch>, "Jani Nikula" <jani.nikula@...el.com>,
 "Lucas De Marchi" <lucas.demarchi@...el.com>,
 "Sumit Semwal" <sumit.semwal@...aro.org>,
 "Alex Deucher" <alexander.deucher@....com>,
 "David Airlie" <airlied@...il.com>, "Gerd Hoffmann" <kraxel@...hat.com>,
 "Dmitry Osipenko" <dmitry.osipenko@...labora.com>,
 "Gurchetan Singh" <gurchetansingh@...omium.org>,
 "Chia-I Wu" <olvaffe@...il.com>,
 "Maarten Lankhorst" <maarten.lankhorst@...ux.intel.com>,
 "Maxime Ripard" <mripard@...nel.org>,
 "Thomas Zimmermann" <tzimmermann@...e.de>,
 Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
 "Rodrigo Vivi" <rodrigo.vivi@...el.com>,
 "Kevin Tian" <kevin.tian@...el.com>, "Joerg Roedel" <joro@...tes.org>,
 "Will Deacon" <will@...nel.org>, "Robin Murphy" <robin.murphy@....com>,
 "Felix Kuehling" <Felix.Kuehling@....com>,
 "Ankit Agrawal" <ankita@...dia.com>,
 "Vivek Kasireddy" <vivek.kasireddy@...el.com>,
 linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org,
 amd-gfx@...ts.freedesktop.org, virtualization@...ts.linux.dev,
 intel-xe@...ts.freedesktop.org, linux-rdma@...r.kernel.org,
 iommu@...ts.linux.dev, kvm@...r.kernel.org
Subject: Re: [PATCH v7 7/8] vfio: Permit VFIO to work with pinned importers



On Thu, Feb 5, 2026, at 7:28 AM, Christian König wrote:
> On 2/5/26 15:21, Jason Gunthorpe wrote:
>> On Thu, Feb 05, 2026 at 02:19:45PM +0200, Leon Romanovsky wrote:
>>> You don't need any backmerge, SHA-1 version of vfio-v6.19-rc8 tag is the
>>> same as in Linus's tree, so the flow is:
>> 
>> I'm confused what is the problem here?
>> 
>> From https://anongit.freedesktop.org/git/drm/drm-misc
>>  * branch                          drm-misc-next -> FETCH_HEAD
>> 
>> $ git show FETCH_HEAD
>> commit 779ec12c85c9e4547519e3903a371a3b26a289de
>> Author: Alexander Konyukhov <Alexander.Konyukhov@...persky.com>
>> Date:   Tue Feb 3 16:48:46 2026 +0300
>> 
>>     drm/komeda: fix integer overflow in AFBC framebuffer size check
>> 
>> $ git merge-base  FETCH_HEAD 61ceaf236115f20f4fdd7cf60f883ada1063349a
>> 24d479d26b25bce5faea3ddd9fa8f3a6c3129ea7
>> $ git describe --contains 24d479d26b25bce5faea3ddd9fa8f3a6c3129ea7
>> v6.19-rc6^0
>> 
>> $ git log --oneline 61ceaf236115f20f4fdd7cf60f883ada1063349a ^FETCH_HEAD
>> 61ceaf236115f2 vfio: Prevent from pinned DMABUF importers to attach to VFIO DMABUF
>> 
>> Just pull Alex's tree, the drm-misc-next tree already has v6.19-rc6,
>> so all they will see is one extra patch from Alex in your PR.
>> 
>> No need to backmerge, this is normal git stuff and there won't be
>> conflicts when they merge a later Linus tag.
>
> Correct, but that would merge the same patch through two different 
> trees. That is usually a pretty big no-go.

Applying the patch through two different trees is a no-go, but merging the same commit from a shared branch or tag is very common and acceptable.  It's the same commit after all, there is no conflict, no duplicate commit.  When the trees are merged, the commit will exist once in the log.  Thanks,

Alex