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[80.230.39.63]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-477bf3558d5sm217203125e9.1.2025.11.24.14.27.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Nov 2025 14:27:56 -0800 (PST) Date: Mon, 24 Nov 2025 17:27:53 -0500 From: "Michael S. Tsirkin" To: Dan Jurgens Cc: netdev@vger.kernel.org, jasowang@redhat.com, pabeni@redhat.com, virtualization@lists.linux.dev, parav@nvidia.com, shshitrit@nvidia.com, yohadt@nvidia.com, xuanzhuo@linux.alibaba.com, eperezma@redhat.com, jgg@ziepe.ca, kevin.tian@intel.com, kuba@kernel.org, andrew+netdev@lunn.ch, edumazet@google.com Subject: Re: [PATCH net-next v12 03/12] virtio: Expose generic device capability operations Message-ID: <20251124172646-mutt-send-email-mst@kernel.org> References: <20251119191524.4572-1-danielj@nvidia.com> <20251119191524.4572-4-danielj@nvidia.com> <20251124152548-mutt-send-email-mst@kernel.org> <29fa4996-38e3-4146-81d3-f8b188e047e9@nvidia.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <29fa4996-38e3-4146-81d3-f8b188e047e9@nvidia.com> On Mon, Nov 24, 2025 at 04:24:37PM -0600, Dan Jurgens wrote: > On 11/24/25 2:30 PM, Michael S. Tsirkin wrote: > > On Wed, Nov 19, 2025 at 01:15:14PM -0600, Daniel Jurgens wrote: > >> Currently querying and setting capabilities is restricted to a single > >> capability and contained within the virtio PCI driver. However, each > >> device type has generic and device specific capabilities, that may be > >> queried and set. In subsequent patches virtio_net will query and set > >> flow filter capabilities. > >> > >> This changes the size of virtio_admin_cmd_query_cap_id_result. It's safe > >> to do because this data is written by DMA, so a newer controller can't > >> overrun the size on an older kernel. > >> > >> Signed-off-by: Daniel Jurgens > >> Reviewed-by: Parav Pandit > >> Reviewed-by: Xuan Zhuo > >> > >> --- > >> v4: Moved this logic from virtio_pci_modern to new file > >> virtio_admin_commands. > >> > >> v12: > >> - Removed uapi virtio_pci include in virtio_admin.h. MST > >> - Added virtio_pci uapi include to virtio_admin_commands.c > >> - Put () around cap in macro. MST > >> - Removed nonsense comment above VIRTIO_ADMIN_MAX_CAP. MST > >> - +1 VIRTIO_ADMIN_MAX_CAP when calculating array size. MST > >> - Updated commit message > >> --- > >> drivers/virtio/Makefile | 2 +- > >> drivers/virtio/virtio_admin_commands.c | 91 ++++++++++++++++++++++++++ > >> include/linux/virtio_admin.h | 80 ++++++++++++++++++++++ > >> include/uapi/linux/virtio_pci.h | 6 +- > >> 4 files changed, 176 insertions(+), 3 deletions(-) > >> create mode 100644 drivers/virtio/virtio_admin_commands.c > >> create mode 100644 include/linux/virtio_admin.h > >> > >> diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile > >> index eefcfe90d6b8..2b4a204dde33 100644 > >> --- a/drivers/virtio/Makefile > >> +++ b/drivers/virtio/Makefile > >> @@ -1,5 +1,5 @@ > >> # SPDX-License-Identifier: GPL-2.0 > >> -obj-$(CONFIG_VIRTIO) += virtio.o virtio_ring.o > >> +obj-$(CONFIG_VIRTIO) += virtio.o virtio_ring.o virtio_admin_commands.o > >> obj-$(CONFIG_VIRTIO_ANCHOR) += virtio_anchor.o > >> obj-$(CONFIG_VIRTIO_PCI_LIB) += virtio_pci_modern_dev.o > >> obj-$(CONFIG_VIRTIO_PCI_LIB_LEGACY) += virtio_pci_legacy_dev.o > >> diff --git a/drivers/virtio/virtio_admin_commands.c b/drivers/virtio/virtio_admin_commands.c > >> new file mode 100644 > >> index 000000000000..a2254e71e8dc > >> --- /dev/null > >> +++ b/drivers/virtio/virtio_admin_commands.c > >> @@ -0,0 +1,91 @@ > >> +// SPDX-License-Identifier: GPL-2.0-only > >> + > >> +#include > >> +#include > >> +#include > >> +#include > >> + > >> +int virtio_admin_cap_id_list_query(struct virtio_device *vdev, > >> + struct virtio_admin_cmd_query_cap_id_result *data) > >> +{ > >> + struct virtio_admin_cmd cmd = {}; > >> + struct scatterlist result_sg; > >> + > >> + if (!vdev->config->admin_cmd_exec) > >> + return -EOPNOTSUPP; > >> + > >> + sg_init_one(&result_sg, data, sizeof(*data)); > >> + cmd.opcode = cpu_to_le16(VIRTIO_ADMIN_CMD_CAP_ID_LIST_QUERY); > >> + cmd.group_type = cpu_to_le16(VIRTIO_ADMIN_GROUP_TYPE_SELF); > >> + cmd.result_sg = &result_sg; > >> + > >> + return vdev->config->admin_cmd_exec(vdev, &cmd); > >> +} > >> +EXPORT_SYMBOL_GPL(virtio_admin_cap_id_list_query); > >> + > >> +int virtio_admin_cap_get(struct virtio_device *vdev, > >> + u16 id, > >> + void *caps, > >> + size_t cap_size) > > > > > > I still don't get why cap_size needs to be as large as size_t. > > > > if you don't care what's it size is, just say "unsigned". > > or u8 as a hint to users it's a small value. > > The size is small for net flow filters, but this is supposed to be a > generic interface for future uses as well. Why limit it? because your implementation makes assumptions - if you want it to be truly generic then you need to handle weird corner cases such as integer overflow when you add these things. > > > > >> +{ > >> + struct virtio_admin_cmd_cap_get_data *data; > >> + struct virtio_admin_cmd cmd = {}; > >> + struct scatterlist result_sg; > >> + struct scatterlist data_sg; > >> + int err; > >> + > >> + if (!vdev->config->admin_cmd_exec) > >> + return -EOPNOTSUPP; > >> + > >> + data = kzalloc(sizeof(*data), GFP_KERNEL); > > > > uses kzalloc without including linux/slab.h > > > > > > > >> + if (!data) > >> + return -ENOMEM; > >> +