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(e.d.c.5.4.7.0.e.f.a.2.f.e.2.0.1.4.d.3.1.6.b.8.0.0.b.8.0.1.0.0.2.ip6.arpa. [2001:8b0:8b6:13d4:102e:f2af:e074:5cde]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-488f585cea1sm52398755e9.15.2026.04.16.06.05.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 16 Apr 2026 06:05:31 -0700 (PDT) Message-ID: <2ea075f9-c80c-41e9-9f93-9b0a2858f68f@meta.com> Date: Thu, 16 Apr 2026 14:05:30 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] vfio/pci: Don't export DMABUFs for unmappable BARs Content-Language: en-GB To: Leon Romanovsky Cc: Alex Williamson , Jason Gunthorpe , Kevin Tian , Vivek Kasireddy , Ankit Agrawal , kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260415181623.1021090-1-mattev@meta.com> <20260416081138.GE361495@unreal> From: Matt Evans In-Reply-To: <20260416081138.GE361495@unreal> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDE2MDEyNSBTYWx0ZWRfX32ca+i2f1NcL vI7CXdeHbI/O3Y4OII18y0hqTy2Rkgzo6+TqbXAY/9tUGxilwuq/BQ/ibpxjwxwrSAsLz2rOEyX M/LOrQcu27TXdkXrHV+ZTt+J6jFCvOCoCkZxYPCpug5z5bMfEHsnAXBPnPFLVIaM89oR2oM6eWC jZjqzdxalltXvl9tCdKdfX5SyLQJIAkZuzkYGxiXeodXYodRuGYxLX3ZEUM1tJNG5NmUx1nv12B egHv4qEzeF2RaSwltS9ibiPd2L5GiHrPc7FlxPEx45YwWPlr9vntN/Nc6YQnDvm71JM+TfrUAnT f+OD9bHyBPYOFirfqWhVj1WsOjmVH+gqxxQq6DABW7oXhnlbedfgIE4RamOQdEVebM0rV+EED9Q vwbFfn1UGBesK9N/x7fqnchYB9RYkFidlj+l3G4zKm1L4x3xVbGegB6Wo5s0oXE7sV4AvmH6Lw8 IlolZa7/w8uWscZe40g== X-Proofpoint-ORIG-GUID: 6nRqHR_0vAfAu-zPYwLvuB5Jp7rkoUPK X-Proofpoint-GUID: 6nRqHR_0vAfAu-zPYwLvuB5Jp7rkoUPK X-Authority-Analysis: v=2.4 cv=cf7iaHDM c=1 sm=1 tr=0 ts=69e0de9d cx=c_pps a=IwH782EDBk/vqbJ9rM8UFw==:117 a=xqWC_Br6kY4A:10 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=7x6HtfJdh03M6CCDgxCd:22 a=jCddH8ec0KUNCymVuxII:22 a=c92rfblmAAAA:8 a=VabnemYjAAAA:8 a=OifCM7uklORgZM6vcRMA:9 a=QEXdDO2ut3YA:10 a=Ng9YvVcppn9CIdWre3nD:22 a=GvGzcOZaWPEFPQC_NcjD:22 a=gKebqoRLp9LExxC7YDUY:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-16_03,2026-04-16_02,2025-10-01_01 Hi Leon, On 16/04/2026 09:11, Leon Romanovsky wrote: > >=20 > On Wed, Apr 15, 2026 at 11:16:23AM -0700, Matt Evans wrote: >> Although vfio_pci_core_feature_dma_buf() validates that both requested >> DMABUF ranges and the PCI resources being referenced are page-aligned, >> there may be reasons other than alignment that cause a BAR to be >> unmappable. >> >> Add a check for vdev->bar_mmap_supported[index], similar to the VFIO >> mmap path. >> >> Fixes: 5d74781ebc86c ("vfio/pci: Add dma-buf export support for MMIO reg= ions") >> Signed-off-by: Matt Evans >> --- >> drivers/vfio/pci/vfio_pci_dmabuf.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c b/drivers/vfio/pci/vfio_= pci_dmabuf.c >> index f87fd32e4a01..4ccaf3531e02 100644 >> --- a/drivers/vfio/pci/vfio_pci_dmabuf.c >> +++ b/drivers/vfio/pci/vfio_pci_dmabuf.c >> @@ -249,6 +249,9 @@ int vfio_pci_core_feature_dma_buf(struct vfio_pci_co= re_device *vdev, u32 flags, >> if (get_dma_buf.region_index >=3D VFIO_PCI_ROM_REGION_INDEX) >> return -ENODEV; >> =20 >> + if (!vdev->bar_mmap_supported[get_dma_buf.region_index]) >> + return -EINVAL; >> + >=20 > And it looks like AI has valid concern about this line too. > https://urldefense.com/v3/__https://sashiko.dev/*/patchset/20260415181623= .1021090-1-mattev@meta.com__;Iw!!Bt8RZUm9aw!5DxsN8cDUviPIZqEjG0pZ_VYYbl_Rdm= WucTGdTZ3ZzlVP_Ysb0n7ykr0eXwFXdpuqvZH2FK3$ Ah, Sashiko has a point, and I think its suggestion of checking lower=20 down in the default .get_dmabuf_phys (vfio_pci_core_get_dmabuf_phys())=20 and preserving driver overrides is decent. Will revisit. To your other question: > I noticed this check in vfio_pci_core_mmap(). Isn't that sufficient? The scenario in mind is doing a DMABUF-export for BARs that you haven't=20 necessarily noticed can't be mmap()ed, and both paths should be checking. Cheers, Matt >=20 > Thanks >=20 >> dma_ranges =3D memdup_array_user(&arg->dma_ranges, get_dma_buf.nr_ran= ges, >> sizeof(*dma_ranges)); >> if (IS_ERR(dma_ranges)) >> --=20 >> 2.47.3 >>