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Tsirkin" To: Yishai Hadas Cc: alex.williamson@redhat.com, jasowang@redhat.com, jgg@nvidia.com, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, parav@nvidia.com, feliu@nvidia.com, jiri@nvidia.com, kevin.tian@intel.com, joao.m.martins@oracle.com, si-wei.liu@oracle.com, leonro@nvidia.com, maorg@nvidia.com Subject: Re: [PATCH V2 vfio 5/9] virtio-pci: Initialize the supported admin commands Message-ID: <20231030192904-mutt-send-email-mst@kernel.org> References: <20231029155952.67686-1-yishaih@nvidia.com> <20231029155952.67686-6-yishaih@nvidia.com> <20231029160750-mutt-send-email-mst@kernel.org> <20231030115541-mutt-send-email-mst@kernel.org> <4e95d66c-c382-4612-8d4b-7ff2b0acd3fb@nvidia.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4e95d66c-c382-4612-8d4b-7ff2b0acd3fb@nvidia.com> On Mon, Oct 30, 2023 at 06:06:45PM +0200, Yishai Hadas wrote: > On 30/10/2023 17:57, Michael S. Tsirkin wrote: > > On Mon, Oct 30, 2023 at 05:27:50PM +0200, Yishai Hadas wrote: > > > On 29/10/2023 22:17, Michael S. Tsirkin wrote: > > > > On Sun, Oct 29, 2023 at 05:59:48PM +0200, Yishai Hadas wrote: > > > > > Initialize the supported admin commands upon activating the admin queue. > > > > > > > > > > The supported commands are saved as part of the admin queue context, it > > > > > will be used by the next patches from this series. > > > > > > > > > > Note: > > > > > As we don't want to let upper layers to execute admin commands before > > > > > that this initialization step was completed, we set ref count to 1 only > > > > > post of that flow and use a non ref counted version command for this > > > > > internal flow. > > > > > > > > > > Signed-off-by: Yishai Hadas > > > > > --- > > > > > drivers/virtio/virtio_pci_common.h | 1 + > > > > > drivers/virtio/virtio_pci_modern.c | 77 +++++++++++++++++++++++++++++- > > > > > 2 files changed, 77 insertions(+), 1 deletion(-) > > > > > > > > > > diff --git a/drivers/virtio/virtio_pci_common.h b/drivers/virtio/virtio_pci_common.h > > > > > index a21b9ba01a60..9e07e556a51a 100644 > > > > > --- a/drivers/virtio/virtio_pci_common.h > > > > > +++ b/drivers/virtio/virtio_pci_common.h > > > > > @@ -46,6 +46,7 @@ struct virtio_pci_admin_vq { > > > > > struct virtio_pci_vq_info info; > > > > > struct completion flush_done; > > > > > refcount_t refcount; > > > > > + u64 supported_cmds; > > > > > /* Name of the admin queue: avq.$index. */ > > > > > char name[10]; > > > > > u16 vq_index; > > > > > diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c > > > > > index ccd7a4d9f57f..25e27aa79cab 100644 > > > > > --- a/drivers/virtio/virtio_pci_modern.c > > > > > +++ b/drivers/virtio/virtio_pci_modern.c > > > > > @@ -19,6 +19,9 @@ > > > > > #define VIRTIO_RING_NO_LEGACY > > > > > #include "virtio_pci_common.h" > > > > > +static int vp_modern_admin_cmd_exec(struct virtio_device *vdev, > > > > > + struct virtio_admin_cmd *cmd); > > > > > + > > > > I don't much like forward declarations. Just order functions sensibly > > > > and they will not be needed. > > > OK, will be part of V3. > > > > > > > > static u64 vp_get_features(struct virtio_device *vdev) > > > > > { > > > > > struct virtio_pci_device *vp_dev = to_vp_device(vdev); > > > > > @@ -59,6 +62,42 @@ vp_modern_avq_set_abort(struct virtio_pci_admin_vq *admin_vq, bool abort) > > > > > WRITE_ONCE(admin_vq->abort, abort); > > > > > } > > > > > +static void virtio_pci_admin_init_cmd_list(struct virtio_device *virtio_dev) > > > > > +{ > > > > > + struct virtio_pci_device *vp_dev = to_vp_device(virtio_dev); > > > > > + struct virtio_admin_cmd cmd = {}; > > > > > + struct scatterlist result_sg; > > > > > + struct scatterlist data_sg; > > > > > + __le64 *data; > > > > > + int ret; > > > > > + > > > > > + data = kzalloc(sizeof(*data), GFP_KERNEL); > > > > > + if (!data) > > > > > + return; > > > > > + > > > > > + sg_init_one(&result_sg, data, sizeof(*data)); > > > > > + cmd.opcode = cpu_to_le16(VIRTIO_ADMIN_CMD_LIST_QUERY); > > > > > + cmd.group_type = cpu_to_le16(VIRTIO_ADMIN_GROUP_TYPE_SRIOV); > > > > > + cmd.result_sg = &result_sg; > > > > > + > > > > > + ret = vp_modern_admin_cmd_exec(virtio_dev, &cmd); > > > > > + if (ret) > > > > > + goto end; > > > > > + > > > > > + sg_init_one(&data_sg, data, sizeof(*data)); > > > > > + cmd.opcode = cpu_to_le16(VIRTIO_ADMIN_CMD_LIST_USE); > > > > > + cmd.data_sg = &data_sg; > > > > > + cmd.result_sg = NULL; > > > > > + > > > > > + ret = vp_modern_admin_cmd_exec(virtio_dev, &cmd); > > > > > + if (ret) > > > > > + goto end; > > > > > + > > > > > + vp_dev->admin_vq.supported_cmds = le64_to_cpu(*data); > > > > > +end: > > > > > + kfree(data); > > > > > +} > > > > > + > > > > > static void vp_modern_avq_activate(struct virtio_device *vdev) > > > > > { > > > > > struct virtio_pci_device *vp_dev = to_vp_device(vdev); > > > > > @@ -67,6 +106,7 @@ static void vp_modern_avq_activate(struct virtio_device *vdev) > > > > > if (!virtio_has_feature(vdev, VIRTIO_F_ADMIN_VQ)) > > > > > return; > > > > > + virtio_pci_admin_init_cmd_list(vdev); > > > > > init_completion(&admin_vq->flush_done); > > > > > refcount_set(&admin_vq->refcount, 1); > > > > > vp_modern_avq_set_abort(admin_vq, false); > > > > > @@ -562,6 +602,35 @@ static bool vp_get_shm_region(struct virtio_device *vdev, > > > > > return true; > > > > > } > > > > > +static int __virtqueue_exec_admin_cmd(struct virtio_pci_admin_vq *admin_vq, > > > > > + struct scatterlist **sgs, > > > > > + unsigned int out_num, > > > > > + unsigned int in_num, > > > > > + void *data, > > > > > + gfp_t gfp) > > > > > +{ > > > > > + struct virtqueue *vq; > > > > > + int ret, len; > > > > > + > > > > > + vq = admin_vq->info.vq; > > > > > + > > > > > + ret = virtqueue_add_sgs(vq, sgs, out_num, in_num, data, gfp); > > > > > + if (ret < 0) > > > > > + return ret; > > > > > + > > > > > + if (unlikely(!virtqueue_kick(vq))) > > > > > + return -EIO; > > > > > + > > > > > + while (!virtqueue_get_buf(vq, &len) && > > > > > + !virtqueue_is_broken(vq)) > > > > > + cpu_relax(); > > > > > + > > > > > + if (virtqueue_is_broken(vq)) > > > > > + return -EIO; > > > > > + > > > > > + return 0; > > > > > +} > > > > > + > > > > This is tolerable I guess but it might pin the CPU for a long time. > > > > The difficulty is handling suprize removal well which we currently > > > > don't do with interrupts. I would say it's ok as is but add > > > > a TODO comments along the lines of /* TODO: use interrupts once these virtqueue_is_broken */ > > > I assume that you asked for adding the below comment before the while loop: > > > /* TODO use interrupts to reduce cpu cycles in the future */ > > > > > > Right ? > > > > > > Yishai > > Well I wrote what I meant. in the future is redundant - everyone knows > > we can't change the past. > > I agree, no need for 'in the future'. > > However, in your suggestion you mentioned  "once these virtqueue_is_broken". > > What does that mean in current polling mode ? > > Yishai Maye better: /* TODO: use vq callback once it supports virtqueue_is_broken */ > > > > > > > static int virtqueue_exec_admin_cmd(struct virtio_pci_admin_vq *admin_vq, > > > > > struct scatterlist **sgs, > > > > > unsigned int out_num, > > > > > @@ -653,7 +722,13 @@ static int vp_modern_admin_cmd_exec(struct virtio_device *vdev, > > > > > in_num++; > > > > > } > > > > > - ret = virtqueue_exec_admin_cmd(&vp_dev->admin_vq, sgs, > > > > > + if (cmd->opcode == VIRTIO_ADMIN_CMD_LIST_QUERY || > > > > > + cmd->opcode == VIRTIO_ADMIN_CMD_LIST_USE) > > > > > + ret = __virtqueue_exec_admin_cmd(&vp_dev->admin_vq, sgs, > > > > > + out_num, in_num, > > > > > + sgs, GFP_KERNEL); > > > > > + else > > > > > + ret = virtqueue_exec_admin_cmd(&vp_dev->admin_vq, sgs, > > > > > out_num, in_num, > > > > > sgs, GFP_KERNEL); > > > > > if (ret) { > > > > > -- > > > > > 2.27.0 >