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([223.233.82.156]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fed7fcd252sm28201655ad.285.2024.07.26.02.58.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Jul 2024 02:58:36 -0700 (PDT) From: Sahil Siddiq X-Google-Original-From: Sahil Siddiq To: eperezma@redhat.com, sgarzare@redhat.com Cc: mst@redhat.com, qemu-devel@nongnu.org, Sahil Siddiq Subject: [RFC v2 0/3] Add packed virtqueue to shadow virtqueue Date: Fri, 26 Jul 2024 15:28:19 +0530 Message-ID: <20240726095822.104017-1-sahilcdq@proton.me> X-Mailer: git-send-email 2.45.2 MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::52b; envelope-from=icegambit91@gmail.com; helo=mail-pg1-x52b.google.com X-Spam_score_int: 15 X-Spam_score: 1.5 X-Spam_bar: + X-Spam_report: (1.5 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no 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 Hi, I have made some progress in this project and thought I would send these changes first before continuing. I split patch v1 [1] into two commits (#1 and #2) to make it easy to review. There are very few changes in the first commit. The second commit has not changes. There are a few things that I am not entirely sure of in commit #3. Q1. In virtio_ring.h [2], new aliases with memory alignment enforcement such as "vring_desc_t" have been created. I am not sure if this is required for the packed vq descriptor ring (vring_packed_desc) as well. I don't see a type alias that enforces memory alignment for "vring_packed_desc" in the linux kernel. I haven't used any alias either. Q2. I see that parts of the "vhost-vdpa" implementation is based on the assumption that SVQ uses the split vq format. For example, "vhost_vdpa_svq_map_rings" [3], calls "vhost_svq_device_area_size" which is specific to split vqs. The "vhost_vring_addr" [4] struct is also specific to split vqs. My idea is to have a generic "vhost_vring_addr" structure that wraps around split and packed vq specific structures, rather than using them directly in if-else conditions wherever the vhost-vdpa functions require their usage. However, this will involve checking their impact in several other places where this struct is currently being used (eg.: "vhost-user", "vhost-backend", "libvhost-user"). Is this approach alright or is there a better alternative? I would like to get your thoughts on this before working on this portion of the project. Thanks, Sahil [1] https://lists.nongnu.org/archive/html/qemu-devel/2024-06/msg03417.html [2] https://gitlab.com/qemu-project/qemu/-/blob/master/include/standard-headers/linux/virtio_ring.h#L149 [3] https://gitlab.com/qemu-project/qemu/-/blob/master/hw/virtio/vhost-vdpa.c#L1178 [4] https://gitlab.com/qemu-project/qemu/-/blob/master/include/standard-headers/linux/vhost_types.h#L30 Changes v1 -> v2: * Split commit from RFC v1 into two commits. * vhost-shadow-virtqueue.c (vhost_svq_add_packed): - Merge with "vhost_svq_vring_write_descs_packed()" - Remove "num == 0" check (vhost_svq_add): Use "is_packed" to check vq format. (vhost_svq_get_vring_addr): Rename function. (vhost_svq_get_vring_addr_packed): New function but is yet to be implemented. (vhost_svq_memory_packed): New function. (vhost_svq_start): Support packed vq format. * vhost-shadow-virtqueue.h (struct VhostShadowVirtqueue): New member "is_packed" (vhost_svq_get_vring_addr): Renamed function. (vhost_svq_get_vring_addr_packed): New function. (vhost_svq_memory_packed): Likewise. * vhost-vdpa.c (vhost_svq_get_vring_addr): Rename function. Sahil Siddiq (3): vhost: Introduce packed vq and add buffer elements vhost: Data structure changes to support packed vqs vhost: Allocate memory for packed vring. hw/virtio/vhost-shadow-virtqueue.c | 161 ++++++++++++++++++++++++++--- hw/virtio/vhost-shadow-virtqueue.h | 76 +++++++++----- hw/virtio/vhost-vdpa.c | 4 +- 3 files changed, 198 insertions(+), 43 deletions(-)