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Message-ID: <CACGkMEtQ7byU0+4EjvwEkHC8FLQ=vb9=k8Z=7mKvvc+MhEGLug@mail.gmail.com>
Date: Mon, 1 Sep 2025 10:31:38 +0800
From: Jason Wang <jasowang@...hat.com>
To: Eugenio Pérez <eperezma@...hat.com>
Cc: "Michael S . Tsirkin" <mst@...hat.com>, Cindy Lu <lulu@...hat.com>,
Stefano Garzarella <sgarzare@...hat.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
Laurent Vivier <lvivier@...hat.com>, virtualization@...ts.linux.dev,
linux-kernel@...r.kernel.org, Yongji Xie <xieyongji@...edance.com>,
Maxime Coquelin <mcoqueli@...hat.com>
Subject: Re: [PATCH 2/6] vduse: add vq group support
On Mon, Sep 1, 2025 at 9:59 AM Jason Wang <jasowang@...hat.com> wrote:
>
> On Tue, Aug 26, 2025 at 7:27 PM Eugenio Pérez <eperezma@...hat.com> wrote:
> >
> > This allows sepparate the different virtqueues in groups that shares the
> > same address space. Asking the VDUSE device for the groups of the vq at
> > the beginning as they're needed for the DMA API.
> >
> > Allocating 3 vq groups as net is the device that need the most groups:
> > * Dataplane (guest passthrough)
> > * CVQ
> > * Shadowed vrings.
> >
> > Future versions of the series can include dynamic allocation of the
> > groups array so VDUSE can declare more groups.
> >
> > Signed-off-by: Eugenio Pérez <eperezma@...hat.com>
> > ---
> > v1: Fix: Remove BIT_ULL(VIRTIO_S_*), as _S_ is already the bit (Maxime)
> >
> > RFC v3:
> > * Increase VDUSE_MAX_VQ_GROUPS to 0xffff (Jason). It was set to a lower
> > value to reduce memory consumption, but vqs are already limited to
> > that value and userspace VDUSE is able to allocate that many vqs.
> > * Remove the descs vq group capability as it will not be used and we can
> > add it on top.
> > * Do not ask for vq groups in number of vq groups < 2.
> > * Move the valid vq groups range check to vduse_validate_config.
> >
> > RFC v2:
> > * Cache group information in kernel, as we need to provide the vq map
> > tokens properly.
> > * Add descs vq group to optimize SVQ forwarding and support indirect
> > descriptors out of the box.
> > ---
> > drivers/vdpa/vdpa_user/vduse_dev.c | 51 ++++++++++++++++++++++++++++--
> > include/uapi/linux/vduse.h | 21 +++++++++++-
> > 2 files changed, 68 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> > index e7bced0b5542..0f4e36dd167e 100644
> > --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> > @@ -58,6 +58,7 @@ struct vduse_virtqueue {
> > struct vdpa_vq_state state;
> > bool ready;
> > bool kicked;
> > + u32 vq_group;
> > spinlock_t kick_lock;
> > spinlock_t irq_lock;
> > struct eventfd_ctx *kickfd;
> > @@ -114,6 +115,7 @@ struct vduse_dev {
> > u8 status;
> > u32 vq_num;
> > u32 vq_align;
> > + u32 ngroups;
> > struct vduse_umem *umem;
> > struct mutex mem_lock;
> > unsigned int bounce_size;
> > @@ -592,6 +594,13 @@ static int vduse_vdpa_set_vq_state(struct vdpa_device *vdpa, u16 idx,
> > return 0;
> > }
> >
> > +static u32 vduse_get_vq_group(struct vdpa_device *vdpa, u16 idx)
> > +{
> > + struct vduse_dev *dev = vdpa_to_vduse(vdpa);
> > +
> > + return dev->vqs[idx]->vq_group;
> > +}
> > +
> > static int vduse_vdpa_get_vq_state(struct vdpa_device *vdpa, u16 idx,
> > struct vdpa_vq_state *state)
> > {
> > @@ -678,6 +687,28 @@ static u8 vduse_vdpa_get_status(struct vdpa_device *vdpa)
> > return dev->status;
> > }
> >
> > +static int vduse_fill_vq_groups(struct vduse_dev *dev)
> > +{
> > + /* All vqs and descs must be in vq group 0 if ngroups < 2 */
> > + if (dev->ngroups < 2)
> > + return 0;
> > +
> > + for (int i = 0; i < dev->vdev->vdpa.nvqs; ++i) {
> > + struct vduse_dev_msg msg = { 0 };
> > + int ret;
> > +
> > + msg.req.type = VDUSE_GET_VQ_GROUP;
> > + msg.req.vq_group.index = i;
> > + ret = vduse_dev_msg_sync(dev, &msg);
> > + if (ret)
> > + return ret;
> > +
> > + dev->vqs[i]->vq_group = msg.resp.vq_group.group;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > static void vduse_vdpa_set_status(struct vdpa_device *vdpa, u8 status)
> > {
> > struct vduse_dev *dev = vdpa_to_vduse(vdpa);
> > @@ -685,6 +716,11 @@ static void vduse_vdpa_set_status(struct vdpa_device *vdpa, u8 status)
> > if (vduse_dev_set_status(dev, status))
> > return;
> >
> > + if (((dev->status ^ status) & VIRTIO_CONFIG_S_FEATURES_OK) &&
> > + (status & VIRTIO_CONFIG_S_FEATURES_OK))
> > + if (vduse_fill_vq_groups(dev))
> > + return;
>
> I may lose some context but I think we've agreed that we need to
> extend the status response for this instead of having multiple
> indepdent response.
Btw, I wonder why don't we get the vq group per .get_vq_group()
Thanks
>
> > +
> > dev->status = status;
> > }
> >
> > @@ -789,6 +825,7 @@ static const struct vdpa_config_ops vduse_vdpa_config_ops = {
> > .set_vq_cb = vduse_vdpa_set_vq_cb,
> > .set_vq_num = vduse_vdpa_set_vq_num,
> > .get_vq_size = vduse_vdpa_get_vq_size,
> > + .get_vq_group = vduse_get_vq_group,
> > .set_vq_ready = vduse_vdpa_set_vq_ready,
> > .get_vq_ready = vduse_vdpa_get_vq_ready,
> > .set_vq_state = vduse_vdpa_set_vq_state,
> > @@ -1737,12 +1774,19 @@ static bool features_is_valid(struct vduse_dev_config *config)
> > return true;
> > }
> >
> > -static bool vduse_validate_config(struct vduse_dev_config *config)
> > +static bool vduse_validate_config(struct vduse_dev_config *config,
> > + u64 api_version)
> > {
> > if (!is_mem_zero((const char *)config->reserved,
> > sizeof(config->reserved)))
> > return false;
> >
> > + if (api_version < VDUSE_API_VERSION_1 && config->ngroups)
> > + return false;
> > +
> > + if (api_version >= VDUSE_API_VERSION_1 && config->ngroups > 0xffff)
> > + return false;
>
> Let's use a macro instead of magic number.
>
> > +
> > if (config->vq_align > PAGE_SIZE)
> > return false;
> >
> > @@ -1858,6 +1902,7 @@ static int vduse_create_dev(struct vduse_dev_config *config,
> > dev->device_features = config->features;
> > dev->device_id = config->device_id;
> > dev->vendor_id = config->vendor_id;
> > + dev->ngroups = (dev->api_version < 1) ? 1 : (config->ngroups ?: 1);
> > dev->name = kstrdup(config->name, GFP_KERNEL);
> > if (!dev->name)
> > goto err_str;
> > @@ -1936,7 +1981,7 @@ static long vduse_ioctl(struct file *file, unsigned int cmd,
> > break;
> >
> > ret = -EINVAL;
> > - if (vduse_validate_config(&config) == false)
> > + if (!vduse_validate_config(&config, control->api_version))
> > break;
> >
> > buf = vmemdup_user(argp + size, config.config_size);
> > @@ -2017,7 +2062,7 @@ static int vduse_dev_init_vdpa(struct vduse_dev *dev, const char *name)
> >
> > vdev = vdpa_alloc_device(struct vduse_vdpa, vdpa, dev->dev,
> > &vduse_vdpa_config_ops, &vduse_map_ops,
> > - 1, 1, name, true);
> > + dev->ngroups, 1, name, true);
> > if (IS_ERR(vdev))
> > return PTR_ERR(vdev);
> >
> > diff --git a/include/uapi/linux/vduse.h b/include/uapi/linux/vduse.h
> > index 9a56d0416bfe..b1c0e47d71fb 100644
> > --- a/include/uapi/linux/vduse.h
> > +++ b/include/uapi/linux/vduse.h
> > @@ -31,6 +31,7 @@
> > * @features: virtio features
> > * @vq_num: the number of virtqueues
> > * @vq_align: the allocation alignment of virtqueue's metadata
> > + * @ngroups: number of vq groups that VDUSE device declares
> > * @reserved: for future use, needs to be initialized to zero
> > * @config_size: the size of the configuration space
> > * @config: the buffer of the configuration space
> > @@ -45,7 +46,8 @@ struct vduse_dev_config {
> > __u64 features;
> > __u32 vq_num;
> > __u32 vq_align;
> > - __u32 reserved[13];
> > + __u32 ngroups; /* if VDUSE_API_VERSION >= 1 */
> > + __u32 reserved[12];
> > __u32 config_size;
> > __u8 config[];
> > };
> > @@ -160,6 +162,16 @@ struct vduse_vq_state_packed {
> > __u16 last_used_idx;
> > };
> >
> > +/**
> > + * struct vduse_vq_group - virtqueue group
> > + * @index: Index of the virtqueue
> > + * @group: Virtqueue group
> > + */
> > +struct vduse_vq_group {
> > + __u32 index;
> > + __u32 group;
> > +};
> > +
> > /**
> > * struct vduse_vq_info - information of a virtqueue
> > * @index: virtqueue index
> > @@ -274,6 +286,7 @@ enum vduse_req_type {
> > VDUSE_GET_VQ_STATE,
> > VDUSE_SET_STATUS,
> > VDUSE_UPDATE_IOTLB,
> > + VDUSE_GET_VQ_GROUP,
> > };
> >
> > /**
> > @@ -316,6 +329,7 @@ struct vduse_iova_range {
> > * @vq_state: virtqueue state, only index field is available
> > * @s: device status
> > * @iova: IOVA range for updating
> > + * @vq_group: virtqueue group of a virtqueue
> > * @padding: padding
> > *
> > * Structure used by read(2) on /dev/vduse/$NAME.
> > @@ -328,6 +342,8 @@ struct vduse_dev_request {
> > struct vduse_vq_state vq_state;
> > struct vduse_dev_status s;
> > struct vduse_iova_range iova;
> > + /* Only if vduse api version >= 1 */;
> > + struct vduse_vq_group vq_group;
> > __u32 padding[32];
> > };
> > };
> > @@ -338,6 +354,7 @@ struct vduse_dev_request {
> > * @result: the result of request
> > * @reserved: for future use, needs to be initialized to zero
> > * @vq_state: virtqueue state
> > + * @vq_group: virtqueue group of a virtqueue
> > * @padding: padding
> > *
> > * Structure used by write(2) on /dev/vduse/$NAME.
> > @@ -350,6 +367,8 @@ struct vduse_dev_response {
> > __u32 reserved[4];
> > union {
> > struct vduse_vq_state vq_state;
> > + /* Only if vduse api version >= 1 */
> > + struct vduse_vq_group vq_group;
> > __u32 padding[32];
> > };
> > };
> > --
> > 2.51.0
> >
>
> Thanks
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