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([2a01:e0a:280:24f0:576b:abc6:6396:ed4a]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4255d8a6b77sm19720721f8f.6.2025.10.06.01.24.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Oct 2025 01:24:06 -0700 (PDT) Message-ID: <9f3e4af2-aa60-434b-8269-706696431882@redhat.com> Date: Mon, 6 Oct 2025 10:24:05 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 6/7] vfio/device: Add support for VFIO_DEVICE_FEATURE_DMA_BUF To: Vivek Kasireddy , qemu-devel@nongnu.org Cc: Alex Williamson References: <20251003234138.85820-1-vivek.kasireddy@intel.com> <20251003234138.85820-7-vivek.kasireddy@intel.com> From: =?UTF-8?Q?C=C3=A9dric_Le_Goater?= 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: <20251003234138.85820-7-vivek.kasireddy@intel.com> 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=-0.43, 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=-0.01, RCVD_IN_MSPIKE_WL=-0.01, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_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 Hello Vivek, On 10/4/25 01:35, Vivek Kasireddy wrote: > In order to implement VFIO_DEVICE_FEATURE_DMA_BUF, we first need > to identify the VFIO region and index the buffer (represented by > iovec) belongs to and then translate its addresses to offsets > within that region. > > The qemu_ram_block_from_host() API gives us both the region and the > offset info we need to populate the dma ranges in order to invoke > this feature. > > Cc: Alex Williamson > Cc: Cédric Le Goater > Signed-off-by: Vivek Kasireddy > --- > hw/vfio/device.c | 43 +++++++++++++++++++++++++++++++++++ > include/hw/vfio/vfio-device.h | 3 +++ > 2 files changed, 46 insertions(+) > > diff --git a/hw/vfio/device.c b/hw/vfio/device.c > index 64f8750389..49070929ac 100644 > --- a/hw/vfio/device.c > +++ b/hw/vfio/device.c > @@ -21,6 +21,7 @@ > #include "qemu/osdep.h" > #include > > +#include "system/ramblock.h" > #include "hw/vfio/vfio-device.h" > #include "hw/vfio/pci.h" > #include "hw/hw.h" > @@ -592,3 +593,45 @@ static VFIODeviceIOOps vfio_device_io_ops_ioctl = { > .region_read = vfio_device_io_region_read, > .region_write = vfio_device_io_region_write, > }; > + > +int vfio_device_create_dmabuf(VFIODevice *vdev, a 'vbasedev' name is preferred for VFIODevice variables/parameters. > + struct iovec *iov, unsigned int iov_cnt) > +{ > + g_autofree struct vfio_device_feature *feature; g_autofree variables should be set: 'feature = NULL' > + struct vfio_device_feature_dma_buf *dma_buf; > + ram_addr_t offset; > + RAMBlock *rb; > + size_t argsz; > + int i, index; > + > + argsz = sizeof(*feature) + sizeof (*dma_buf) + > + sizeof(struct vfio_region_dma_range) * iov_cnt; > + feature = g_malloc0(argsz); > + dma_buf = (struct vfio_device_feature_dma_buf *)feature->data; > + > + for (i = 0; i < iov_cnt; i++) { > + rcu_read_lock(); Is it needed ? > + rb = qemu_ram_block_from_host(iov[i].iov_base, false, &offset); > + rcu_read_unlock(); > + > + if (!rb) { > + return -1; wouldn't an errno be more appropriate ? > + } > + > + index = vfio_get_region_index_from_mr(rb->mr); > + if (index < 0) { > + return -1; > + } > + > + dma_buf->region_index = index; > + dma_buf->dma_ranges[i].offset = offset; > + dma_buf->dma_ranges[i].length = iov[i].iov_len; > + } > + > + dma_buf->nr_ranges = iov_cnt; > + dma_buf->open_flags = O_RDONLY | O_CLOEXEC; > + feature->argsz = argsz; > + feature->flags = VFIO_DEVICE_FEATURE_GET | VFIO_DEVICE_FEATURE_DMA_BUF; > + > + return ioctl(vdev->fd, VFIO_DEVICE_FEATURE, feature); Please use : return vbasedev->io_ops->device_feature(vbasedev, feature); This would be returning an errno. Callers should be aware. > +} > diff --git a/include/hw/vfio/vfio-device.h b/include/hw/vfio/vfio-device.h > index bdb106c937..74b3c4eef7 100644 > --- a/include/hw/vfio/vfio-device.h > +++ b/include/hw/vfio/vfio-device.h > @@ -279,6 +279,9 @@ int vfio_device_get_irq_info(VFIODevice *vbasedev, int index, > struct vfio_irq_info *info); > > int vfio_get_region_index_from_mr(MemoryRegion *mr); > + > +int vfio_device_create_dmabuf(VFIODevice *vbasedev, > + struct iovec *iov, unsigned int iov_cnt); Since this is an external routine, please add documentation. Thanks, C. > #endif > > /* Returns 0 on success, or a negative errno. */