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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 ffacd0b85a97d-4541282046esm408713f8f.8.2026.05.07.10.17.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 07 May 2026 10:17:54 -0700 (PDT) Message-ID: Date: Thu, 7 May 2026 18:17:53 +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 5/9] vfio/pci: Provide a user-facing name for BAR mappings From: Matt Evans To: Alex Williamson Cc: Leon Romanovsky , Jason Gunthorpe , Alex Mastro , =?UTF-8?Q?Christian_K=C3=B6nig?= , Mahmoud Adam , David Matlack , =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , Sumit Semwal , Kevin Tian , Ankit Agrawal , Pranjal Shrivastava , Alistair Popple , Vivek Kasireddy , linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, kvm@vger.kernel.org References: <20260416131815.2729131-1-mattev@meta.com> <20260416131815.2729131-6-mattev@meta.com> <20260501164430.5d3ea683@shazbot.org> <7d370a5d-3730-42f0-8656-14ad9c0da682@meta.com> Content-Language: en-GB In-Reply-To: <7d370a5d-3730-42f0-8656-14ad9c0da682@meta.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Authority-Analysis: v=2.4 cv=Vc3H+lp9 c=1 sm=1 tr=0 ts=69fcc945 cx=c_pps a=CsXZvLRfiTx/ye2xXAwb9g==:117 a=xqWC_Br6kY4A:10 a=IkcTkHD0fZMA:10 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=7x6HtfJdh03M6CCDgxCd:22 a=03ozwUkBphtHgyqjj1sw:22 a=VwQbUJbxAAAA:8 a=VabnemYjAAAA:8 a=gEb6E3g4VIbv0AVgNvMA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=F7q00xkr9EfWfQvbdVXI:22 a=gKebqoRLp9LExxC7YDUY:22 X-Proofpoint-GUID: mdUlmyAxTe_MEhJQFM-wc1XZktPiy1Dg X-Proofpoint-ORIG-GUID: mdUlmyAxTe_MEhJQFM-wc1XZktPiy1Dg X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTA3MDE3MyBTYWx0ZWRfX3Yh/imo9QatI DfWFtb6+PRiOuRGYk9CeZyCx09NJdRvoTUZh5nVRtRKGX8oP7QQ0pWEpfWEPUbG+uzlIyFJJPbB vnxnnceZe15qEkmZ4CAWfkSBCFs4pljQL3pOcKihyMqRlWMrYwrUcRAA4whZA7bVqgVxcl66Ml0 3r4ipiB2Xg08emwq6MBzXCfmVMLo4BNFah50d95649O6XFedOstrJXplB2do8/oSIlud2m+pJZF l/KZxN8SY6MtqRLqWK41nECRLBjEWdb8sp3Zx40ZAfklnBmhqMipLaZp/WDGxFMZPWxyBPl+Ed6 RavxKwtiYJYsYwIGsciDPn4Fgt8HA/K2X2r8ca13rSW4tx+TA1QNu/WKyEbKk608HmQ0hX3f0Is ncZYNhL4igwqz+A4Uv+B8zFEHcMjBV9TtRtfYLgDJWgiSJLbWBL6FoTxJVsKvzY7qocKpKyPgqQ H7w19gBz1+BooSE34Lg== 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=2026-05-07_02,2026-05-06_01,2025-10-01_01 Sent too soon, :| On 07/05/2026 17:56, Matt Evans wrote: > Hi Alex, > > On 01/05/2026 23:44, Alex Williamson wrote: >> >> On Thu, 16 Apr 2026 06:17:48 -0700 >> Matt Evans wrote: >> >>> Since converting BAR mmap()s to using DMABUFs, we lose the original >>> device path in /proc//maps, lsof, etc.  Generate a debug-oriented >>> synthetic 'filename' based on the cdev, plus BDF, plus resource index. >>> >>> This applies only to BAR mappings via the VFIO device fd, as >>> explicitly-exported DMABUFs are named by userspace via the >>> DMA_BUF_SET_NAME ioctl. >>> >>> Signed-off-by: Matt Evans >>> --- >>>   drivers/vfio/pci/vfio_pci_dmabuf.c | 27 +++++++++++++++++++++++++-- >>>   1 file changed, 25 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c b/drivers/vfio/pci/ >>> vfio_pci_dmabuf.c >>> index a12432825e5e..04c7733fe712 100644 >>> --- a/drivers/vfio/pci/vfio_pci_dmabuf.c >>> +++ b/drivers/vfio/pci/vfio_pci_dmabuf.c >>> @@ -4,6 +4,7 @@ >>>   #include >>>   #include >>>   #include >>> +#include >>>   #include "vfio_pci_priv.h" >>> @@ -467,6 +468,7 @@ int vfio_pci_core_mmap_prep_dmabuf(struct >>> vfio_pci_core_device *vdev, >>>   { >>>       struct vfio_pci_dma_buf *priv; >>>       const unsigned int nr_ranges = 1; >>> +    char *bufname; >>>       int ret; >>>       priv = kzalloc_obj(*priv); >>> @@ -479,6 +481,20 @@ int vfio_pci_core_mmap_prep_dmabuf(struct >>> vfio_pci_core_device *vdev, >>>           goto err_free_priv; >>>       } >>> +    bufname = kzalloc(DMA_BUF_NAME_LEN, GFP_KERNEL); >>> +    if (!bufname) { >>> +        ret = -ENOMEM; >>> +        goto err_free_phys; >>> +    } >>> + >>> +    /* >>> +     * Maximum size of the friendly debug name is >>> +     * vfio1234567890:ffff:ff:3f.7-9 = 30, which fits within >>> +     * DMA_BUF_NAME_LEN. >>> +     */ >>> +    snprintf(bufname, DMA_BUF_NAME_LEN, "%s:%s/%x", >>> +         dev_name(&vdev->vdev.device), pci_name(vdev->pdev), >>> res_index); >> >> Comment suggests 9 is the max res_index that can be printed, but mmap >> only directly supports standard BARs 0-5.  Comment also uses a '-' >> while the code uses a '/'.  Thanks, > > Right you are.  Fixed, but, since... > https://lore.kernel.org/kvm/52162da4-e1cc-4f90-a95a-218d6089cd71@meta.com/ > > ...I'm keeping the resource index encoded in the vm_pgoffs and as that's > in /proc//maps it doesn't need to be in the name. I.e., an example > mapping of BAR 2 looks like: > > ffffa9330000-ffffad300000 rw-s 20000030000 00:0b 12 / > dmabuf:vfio0:0000:00:03.0 BUT, the name's visible via paths other than just /proc//maps, e.g. /sys/kernel/debug/dma_buf/bufinfo or /proc//map_files which don't have the vm_offs, and so back to plan A. Just made the comment consistent. Matt