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Tue, 18 Nov 2025 15:10:45 -0500 (EST) Date: Tue, 18 Nov 2025 13:10:38 -0700 From: Alex Williamson To: "Tian, Kevin" Cc: Leon Romanovsky , Bjorn Helgaas , Logan Gunthorpe , Jens Axboe , "Robin Murphy" , Joerg Roedel , Will Deacon , Marek Szyprowski , "Jason Gunthorpe" , Andrew Morton , Jonathan Corbet , Sumit Semwal , Christian =?UTF-8?B?S8O2bmln?= , Kees Cook , "Gustavo A. R. Silva" , "Ankit Agrawal" , Yishai Hadas , "Shameer Kolothum" , Krishnakant Jaju , Matt Ochs , "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-block@vger.kernel.org" , "iommu@lists.linux.dev" , "linux-mm@kvack.org" , "linux-doc@vger.kernel.org" , "linux-media@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , "linaro-mm-sig@lists.linaro.org" , "kvm@vger.kernel.org" , "linux-hardening@vger.kernel.org" , Alex Mastro , Nicolin Chen Subject: Re: [PATCH v8 09/11] vfio/pci: Enable peer-to-peer DMA transactions by default Message-ID: <20251118131038.32b7804d.alex@shazbot.org> In-Reply-To: References: <20251111-dmabuf-vfio-v8-0-fd9aa5df478f@nvidia.com> <20251111-dmabuf-vfio-v8-9-fd9aa5df478f@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 44AFF4000F X-Stat-Signature: 39pxunqadq43mauzrcmikiziannje1x4 X-Rspam-User: X-HE-Tag: 1763496652-160674 X-HE-Meta: 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 DYb5S0n6 dhs4t/AZd3IcM/Nz5upHZenVBauv2DOAkjfOOPzXHeNbC8PSzRElhvVbzHNoY+undL+HGlhUDdCshO6f99Lyx62o+btoegLTTh2ywquH4B0Tk0fv5h8XI3OPgYdo+UKLCs8RsG0MauVx3HikDENw7W+dHhig28ULkrvO5c7DuAJxU+axN7gbHinTDUzK1qmMYUzoxrUCqNTgGV8/WmR1n39ydv8HbZIsfv9SVz5EepXa+/ns0QcPY1dP8yuwsZCjT1m8HF8huSsB1xlMHYjQCcTBAfFDlDRHUEyfHRfYEQRLMDIYUrWqKl5P2l9YhD245ii9+jEGaoRpwrlldn0223o1mygCzJyjzdfau6AA62kbhGa06IJVcrElxSalKKVMZhyMdhmu7YVD4X504GhcYReUyxUgRmlMRZao9p0OKIbSwqeZlnRzH5JsV8Cd6DixbOIL6XZQHEKc1ihgOAaJJ8dGS4g== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 18 Nov 2025 07:18:36 +0000 "Tian, Kevin" wrote: > > From: Leon Romanovsky > > Sent: Tuesday, November 11, 2025 5:58 PM > > > > From: Leon Romanovsky > > not required with only your own s-o-b > > > @@ -2090,6 +2092,9 @@ int vfio_pci_core_init_dev(struct vfio_device > > *core_vdev) > > INIT_LIST_HEAD(&vdev->dummy_resources_list); > > INIT_LIST_HEAD(&vdev->ioeventfds_list); > > INIT_LIST_HEAD(&vdev->sriov_pfs_item); > > + ret = pcim_p2pdma_init(vdev->pdev); > > + if (ret && ret != -EOPNOTSUPP) > > + return ret; > > Reading the commit msg seems -EOPNOTSUPP is only returned for fake > PCI devices, otherwise it implies regression. better add a comment for it? I think the commit log is saying that if a device comes along that can't support this, we'd quirk the init path to return -EOPNOTSUPP for that particular device here. This path is currently used when !CONFIG_PCI_P2PDMA to make this error non-fatal to the device init. I don't see a regression if such a device comes along and while we could survive other types of failures by disabling p2pdma here, I think all such cases are sufficient rare out of memory cases to consider them catastrophic. Thanks, Alex