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([2a01:e0a:280:24f0:576b:abc6:6396:ed4a]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46fa3a0d17fsm10508495e9.4.2025.10.06.23.51.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Oct 2025 23:51:58 -0700 (PDT) Message-ID: Date: Tue, 7 Oct 2025 08:51:57 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 7/7] virtio-gpu-udmabuf: Create dmabuf for blobs associated with VFIO devices From: =?UTF-8?Q?C=C3=A9dric_Le_Goater?= To: Vivek Kasireddy , qemu-devel@nongnu.org Cc: =?UTF-8?Q?Marc-Andr=C3=A9_Lureau?= , =?UTF-8?Q?Alex_Benn=C3=A9e?= , Akihiko Odaki , Dmitry Osipenko References: <20251003234138.85820-1-vivek.kasireddy@intel.com> <20251003234138.85820-8-vivek.kasireddy@intel.com> Content-Language: en-US, fr Autocrypt: addr=clg@redhat.com; keydata= xsFNBFu8o3UBEADP+oJVJaWm5vzZa/iLgpBAuzxSmNYhURZH+guITvSySk30YWfLYGBWQgeo 8NzNXBY3cH7JX3/a0jzmhDc0U61qFxVgrPqs1PQOjp7yRSFuDAnjtRqNvWkvlnRWLFq4+U5t yzYe4SFMjFb6Oc0xkQmaK2flmiJNnnxPttYwKBPd98WfXMmjwAv7QfwW+OL3VlTPADgzkcqj 53bfZ4VblAQrq6Ctbtu7JuUGAxSIL3XqeQlAwwLTfFGrmpY7MroE7n9Rl+hy/kuIrb/TO8n0 ZxYXvvhT7OmRKvbYuc5Jze6o7op/bJHlufY+AquYQ4dPxjPPVUT/DLiUYJ3oVBWFYNbzfOrV RxEwNuRbycttMiZWxgflsQoHF06q/2l4ttS3zsV4TDZudMq0TbCH/uJFPFsbHUN91qwwaN/+ gy1j7o6aWMz+Ib3O9dK2M/j/O/Ube95mdCqN4N/uSnDlca3YDEWrV9jO1mUS/ndOkjxa34ia 70FjwiSQAsyIwqbRO3CGmiOJqDa9qNvd2TJgAaS2WCw/TlBALjVQ7AyoPEoBPj31K74Wc4GS Rm+FSch32ei61yFu6ACdZ12i5Edt+To+hkElzjt6db/UgRUeKfzlMB7PodK7o8NBD8outJGS tsL2GRX24QvvBuusJdMiLGpNz3uqyqwzC5w0Fd34E6G94806fwARAQABzSJDw6lkcmljIExl IEdvYXRlciA8Y2xnQHJlZGhhdC5jb20+wsGRBBMBCAA7FiEEoPZlSPBIlev+awtgUaNDx8/7 7KEFAmTLlVECGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgkQUaNDx8/77KG0eg// S0zIzTcxkrwJ/9XgdcvVTnXLVF9V4/tZPfB7sCp8rpDCEseU6O0TkOVFoGWM39sEMiQBSvyY lHrP7p7E/JYQNNLh441MfaX8RJ5Ul3btluLapm8oHp/vbHKV2IhLcpNCfAqaQKdfk8yazYhh EdxTBlzxPcu+78uE5fF4wusmtutK0JG0sAgq0mHFZX7qKG6LIbdLdaQalZ8CCFMKUhLptW71 xe+aNrn7hScBoOj2kTDRgf9CE7svmjGToJzUxgeh9mIkxAxTu7XU+8lmL28j2L5uNuDOq9vl hM30OT+pfHmyPLtLK8+GXfFDxjea5hZLF+2yolE/ATQFt9AmOmXC+YayrcO2ZvdnKExZS1o8 VUKpZgRnkwMUUReaF/mTauRQGLuS4lDcI4DrARPyLGNbvYlpmJWnGRWCDguQ/LBPpbG7djoy k3NlvoeA757c4DgCzggViqLm0Bae320qEc6z9o0X0ePqSU2f7vcuWN49Uhox5kM5L86DzjEQ RHXndoJkeL8LmHx8DM+kx4aZt0zVfCHwmKTkSTQoAQakLpLte7tWXIio9ZKhUGPv/eHxXEoS 0rOOAZ6np1U/xNR82QbF9qr9TrTVI3GtVe7Vxmff+qoSAxJiZQCo5kt0YlWwti2fFI4xvkOi V7lyhOA3+/3oRKpZYQ86Frlo61HU3r6d9wzOwU0EW7yjdQEQALyDNNMw/08/fsyWEWjfqVhW pOOrX2h+z4q0lOHkjxi/FRIRLfXeZjFfNQNLSoL8j1y2rQOs1j1g+NV3K5hrZYYcMs0xhmrZ KXAHjjDx7FW3sG3jcGjFW5Xk4olTrZwFsZVUcP8XZlArLmkAX3UyrrXEWPSBJCXxDIW1hzwp bV/nVbo/K9XBptT/wPd+RPiOTIIRptjypGY+S23HYBDND3mtfTz/uY0Jytaio9GETj+fFis6 TxFjjbZNUxKpwftu/4RimZ7qL+uM1rG1lLWc9SPtFxRQ8uLvLOUFB1AqHixBcx7LIXSKZEFU CSLB2AE4wXQkJbApye48qnZ09zc929df5gU6hjgqV9Gk1rIfHxvTsYltA1jWalySEScmr0iS YBZjw8Nbd7SxeomAxzBv2l1Fk8fPzR7M616dtb3Z3HLjyvwAwxtfGD7VnvINPbzyibbe9c6g LxYCr23c2Ry0UfFXh6UKD83d5ybqnXrEJ5n/t1+TLGCYGzF2erVYGkQrReJe8Mld3iGVldB7 JhuAU1+d88NS3aBpNF6TbGXqlXGF6Yua6n1cOY2Yb4lO/mDKgjXd3aviqlwVlodC8AwI0Sdu jWryzL5/AGEU2sIDQCHuv1QgzmKwhE58d475KdVX/3Vt5I9kTXpvEpfW18TjlFkdHGESM/Jx IqVsqvhAJkalABEBAAHCwV8EGAECAAkFAlu8o3UCGwwACgkQUaNDx8/77KEhwg//WqVopd5k 8hQb9VVdk6RQOCTfo6wHhEqgjbXQGlaxKHoXywEQBi8eULbeMQf5l4+tHJWBxswQ93IHBQjK yKyNr4FXseUI5O20XVNYDJZUrhA4yn0e/Af0IX25d94HXQ5sMTWr1qlSK6Zu79lbH3R57w9j hQm9emQEp785ui3A5U2Lqp6nWYWXz0eUZ0Tad2zC71Gg9VazU9MXyWn749s0nXbVLcLS0yop s302Gf3ZmtgfXTX/W+M25hiVRRKCH88yr6it+OMJBUndQVAA/fE9hYom6t/zqA248j0QAV/p LHH3hSirE1mv+7jpQnhMvatrwUpeXrOiEw1nHzWCqOJUZ4SY+HmGFW0YirWV2mYKoaGO2YBU wYF7O9TI3GEEgRMBIRT98fHa0NPwtlTktVISl73LpgVscdW8yg9Gc82oe8FzU1uHjU8b10lU XOMHpqDDEV9//r4ZhkKZ9C4O+YZcTFu+mvAY3GlqivBNkmYsHYSlFsbxc37E1HpTEaSWsGfA HQoPn9qrDJgsgcbBVc1gkUT6hnxShKPp4PlsZVMNjvPAnr5TEBgHkk54HQRhhwcYv1T2QumQ izDiU6iOrUzBThaMhZO3i927SG2DwWDVzZltKrCMD1aMPvb3NU8FOYRhNmIFR3fcalYr+9gD uVKe8BVz4atMOoktmt0GWTOC8P4= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=clg@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.441, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 10/6/25 17:59, Cédric Le Goater wrote: > On 10/4/25 01:36, Vivek Kasireddy wrote: >> In addition to memfd, a blob resource can also have its backing >> storage in a VFIO device region. Therefore, we first need to figure >> out if the blob is backed by a VFIO device region or a memfd before >> we can call the right API to get a dmabuf fd created. >> >> So, once we have the ramblock and the associated mr, we rely on >> memory_region_is_ram_device() to tell us where the backing storage >> is located. If the blob resource is VFIO backed, we try to find the >> right VFIO device that contains the blob and then invoke the API >> vfio_device_create_dmabuf(). >> >> Note that in virtio_gpu_remap_udmabuf(), we first try to test if >> the VFIO dmabuf exporter supports mmap or not. If it doesn't, we >> use the VFIO device fd directly to create the CPU mapping. >> >> Cc: Marc-André Lureau >> Cc: Alex Bennée >> Cc: Akihiko Odaki >> Cc: Dmitry Osipenko >> Signed-off-by: Vivek Kasireddy >> --- >>   hw/display/Kconfig              |   5 ++ >>   hw/display/virtio-gpu-udmabuf.c | 143 ++++++++++++++++++++++++++++++-- >>   2 files changed, 141 insertions(+), 7 deletions(-) >> >> diff --git a/hw/display/Kconfig b/hw/display/Kconfig >> index 1e95ab28ef..0d090f25f5 100644 >> --- a/hw/display/Kconfig >> +++ b/hw/display/Kconfig >> @@ -106,6 +106,11 @@ config VIRTIO_VGA >>       depends on VIRTIO_PCI >>       select VGA >> +config VIRTIO_GPU_VFIO_BLOB >> +    bool >> +    default y >> +    depends on VFIO >> + >>   config VHOST_USER_GPU >>       bool >>       default y >> diff --git a/hw/display/virtio-gpu-udmabuf.c b/hw/display/virtio-gpu-udmabuf.c >> index d804f321aa..bd06b4f300 100644 >> --- a/hw/display/virtio-gpu-udmabuf.c >> +++ b/hw/display/virtio-gpu-udmabuf.c >> @@ -18,6 +18,7 @@ >>   #include "ui/console.h" >>   #include "hw/virtio/virtio-gpu.h" >>   #include "hw/virtio/virtio-gpu-pixman.h" >> +#include "hw/vfio/vfio-device.h" >>   #include "trace.h" >>   #include "system/ramblock.h" >>   #include "system/hostmem.h" >> @@ -27,6 +28,33 @@ >>   #include "standard-headers/linux/udmabuf.h" >>   #include "standard-headers/drm/drm_fourcc.h" >> +static void vfio_create_dmabuf(VFIODevice *vdev, >> +                               struct virtio_gpu_simple_resource *res) >> +{ >> +#if defined(VIRTIO_GPU_VFIO_BLOB) >> +    res->dmabuf_fd = vfio_device_create_dmabuf(vdev, res->iov, res->iov_cnt); > > I didn't realize an fd was returned until this patch. I'd suggest > renaming vfio_device_create_dmabuf() to vfio_device_create_dmabuf_fd(), > or something explicit IMO. > >> +    if (res->dmabuf_fd < 0) { >> +        qemu_log_mask(LOG_GUEST_ERROR, >> +                      "%s: VFIO_DEVICE_FEATURE_DMA_BUF: %s\n", >> +                      __func__, strerror(errno)); >> +    } >> +#endif >> +} >> + >> +static VFIODevice *vfio_device_lookup(MemoryRegion *mr) >> +{ >> +#if defined(VIRTIO_GPU_VFIO_BLOB) >> +    VFIODevice *vdev; >> + >> +    QLIST_FOREACH(vdev, &vfio_device_list, next) { > Hmm, I'm not sure we want to expose the VFIOdevice list to other > subsystems. I understand the need, and it's faster than iterating > over QOM devices, but I’d prefer that an API be provided for this > purpose. > > I missed how much vfio_device_list has proliferated. Needs a check. > > >> +        if (vdev->dev == mr->dev) { >> +            return vdev; >> +        } >> +    } >> +#endif >> +    return NULL; >> +} >> + >>   static void virtio_gpu_create_udmabuf(struct virtio_gpu_simple_resource *res) >>   { >>       struct udmabuf_create_list *list; >> @@ -68,11 +96,73 @@ static void virtio_gpu_create_udmabuf(struct virtio_gpu_simple_resource *res) >>       g_free(list); >>   } >> -static void virtio_gpu_remap_udmabuf(struct virtio_gpu_simple_resource *res) >> +static void *vfio_dmabuf_mmap(struct virtio_gpu_simple_resource *res, >> +                              VFIODevice *vdev) >> +{ >> +    struct vfio_region_info *info; >> +    ram_addr_t offset, len = 0; >> +    void *map, *submap; >> +    int i, ret = -1; >> +    RAMBlock *rb; >> + >> +    /* >> +     * We first reserve a contiguous chunk of address space for the entire >> +     * dmabuf, then replace it with smaller mappings that correspond to the >> +     * individual segments of the dmabuf. >> +     */ >> +    map = mmap(NULL, res->blob_size, PROT_READ, MAP_SHARED, vdev->fd, 0); >> +    if (map == MAP_FAILED) { >> +        return map; >> +    } >> + >> +    for (i = 0; i < res->iov_cnt; i++) { >> +        rcu_read_lock(); >> +        rb = qemu_ram_block_from_host(res->iov[i].iov_base, false, &offset); >> +        rcu_read_unlock(); >> + >> +        if (!rb) { >> +            goto err; >> +        } >> + >> +#if defined(VIRTIO_GPU_VFIO_BLOB) >> +        ret = vfio_get_region_index_from_mr(rb->mr); >> +        if (ret < 0) { >> +            goto err; >> +        } >> + >> +        ret = vfio_device_get_region_info(vdev, ret, &info); >> +#endif >> +        if (ret < 0) { >> +            goto err; >> +        } > > "hmm" again. Not this patch fault but we lack proper documentation > for the VFIO API. Something to work on. Since this patch is using > vfio_device_get_region_info() could you please add documentation > for it ? > > > Thanks, > > C. > > > >> +        submap = mmap(map + len, res->iov[i].iov_len, PROT_READ, >> +                      MAP_SHARED | MAP_FIXED, vdev->fd, >> +                      info->offset + offset); One more thing which needs a fix : 'info' is uninitialized if !VIRTIO_GPU_VFIO_BLOB. Thanks, C. >> +        if (submap == MAP_FAILED) { >> +            goto err; >> +        } >> + >> +        len += res->iov[i].iov_len; >> +    } >> +    return map; >> +err: >> +    munmap(map, res->blob_size); >> +    return MAP_FAILED; >> +} >> + >> +static void virtio_gpu_remap_udmabuf(struct virtio_gpu_simple_resource *res, >> +                                     VFIODevice *vdev) >>   { >>       res->remapped = mmap(NULL, res->blob_size, PROT_READ, >>                            MAP_SHARED, res->dmabuf_fd, 0); >>       if (res->remapped == MAP_FAILED) { >> +        if (vdev) { >> +            res->remapped = vfio_dmabuf_mmap(res, vdev); >> +            if (res->remapped != MAP_FAILED) { >> +                return; >> +            } >> +        } >>           warn_report("%s: dmabuf mmap failed: %s", __func__, >>                       strerror(errno)); >>           res->remapped = NULL; >> @@ -130,18 +220,59 @@ bool virtio_gpu_have_udmabuf(void) >>   void virtio_gpu_init_udmabuf(struct virtio_gpu_simple_resource *res) >>   { >> +    VFIODevice *vdev = NULL; >>       void *pdata = NULL; >> +    ram_addr_t offset; >> +    RAMBlock *rb; >>       res->dmabuf_fd = -1; >>       if (res->iov_cnt == 1 && >>           res->iov[0].iov_len < 4096) { >>           pdata = res->iov[0].iov_base; >>       } else { >> -        virtio_gpu_create_udmabuf(res); >> -        if (res->dmabuf_fd < 0) { >> +        rcu_read_lock(); >> +        rb = qemu_ram_block_from_host(res->iov[0].iov_base, false, &offset); >> +        rcu_read_unlock(); >> + >> +        if (!rb) { >> +            qemu_log_mask(LOG_GUEST_ERROR, >> +                          "%s: Could not find ram block for host address\n", >> +                          __func__); >>               return; >>           } >> -        virtio_gpu_remap_udmabuf(res); >> + >> +        if (memory_region_is_ram_device(rb->mr)) { >> +            vdev = vfio_device_lookup(rb->mr); >> +            if (!vdev) { >> +                qemu_log_mask(LOG_GUEST_ERROR, >> +                              "%s: Could not find device to create dmabuf\n", >> +                              __func__); >> +                return; >> +            } >> + >> +            vfio_create_dmabuf(vdev, res); >> +            if (res->dmabuf_fd < 0) { >> +                qemu_log_mask(LOG_GUEST_ERROR, >> +                              "%s: Could not create dmabuf from vfio device\n", >> +                              __func__); >> +                return; >> +            } >> +        } else if (memory_region_is_ram(rb->mr) && virtio_gpu_have_udmabuf()) { >> +            virtio_gpu_create_udmabuf(res); >> +            if (res->dmabuf_fd < 0) { >> +                qemu_log_mask(LOG_GUEST_ERROR, >> +                              "%s: Could not create dmabuf from memfd\n", >> +                              __func__); >> +                return; >> +            } >> +        } else { >> +            qemu_log_mask(LOG_GUEST_ERROR, >> +                          "%s: memory region cannot be used to create dmabuf\n", >> +                          __func__); >> +            return; >> +        } >> + >> +        virtio_gpu_remap_udmabuf(res, vdev); >>           if (!res->remapped) { >>               return; >>           } >> @@ -153,9 +284,7 @@ void virtio_gpu_init_udmabuf(struct virtio_gpu_simple_resource *res) >>   void virtio_gpu_fini_udmabuf(struct virtio_gpu_simple_resource *res) >>   { >> -    if (res->remapped) { >> -        virtio_gpu_destroy_udmabuf(res); >> -    } >> +    virtio_gpu_destroy_udmabuf(res); >>   } >>   static void virtio_gpu_free_dmabuf(VirtIOGPU *g, VGPUDMABuf *dmabuf) >