Re: [PATCH v3 3/6] vduse: add vq group support

Jason Wang
2025-09-22T01:16:04Z

On Fri, Sep 19, 2025 at 5:34 PM Eugenio Pérez <eperezma@redhat.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@redhat.com>
> ---
> v3:
> * Make the default group an invalid group as long as VDUSE device does
> not set it to some valid u32 value. Modify the vdpa core to take that
> into account (Jason).
> * Create the VDUSE_DEV_MAX_GROUPS instead of using a magic number
>
> v2:
> * Now the vq group is in vduse_vq_config struct instead of issuing one
> VDUSE message per vq.
>
> 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/ifcvf/ifcvf_main.c | 2 +-
> drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
> drivers/vdpa/vdpa_sim/vdpa_sim.c | 2 +-
> drivers/vdpa/vdpa_user/vduse_dev.c | 51 +++++++++++++++++++++++++++---
> drivers/vhost/vdpa.c | 11 +++++--
> include/linux/vdpa.h | 5 +--
> include/uapi/linux/vduse.h | 12 +++++--
> 7 files changed, 69 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c b/drivers/vdpa/ifcvf/ifcvf_main.c
> index 6658dc74d915..ea6643760fb7 100644
> --- a/drivers/vdpa/ifcvf/ifcvf_main.c
> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
> @@ -559,7 +559,7 @@ static size_t ifcvf_vdpa_get_config_size(struct vdpa_device *vdpa_dev)
> return vf->config_size;
> }
>
> -static u32 ifcvf_vdpa_get_vq_group(struct vdpa_device *vdpa, u16 idx)
> +static s64 ifcvf_vdpa_get_vq_group(struct vdpa_device *vdpa, u16 idx)
> {
> return 0;
> }
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 82034efb74fc..daab0ccb78b2 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -2640,7 +2640,7 @@ static u32 mlx5_vdpa_get_vq_align(struct vdpa_device *vdev)
> return PAGE_SIZE;
> }
>
> -static u32 mlx5_vdpa_get_vq_group(struct vdpa_device *vdev, u16 idx)
> +static s64 mlx5_vdpa_get_vq_group(struct vdpa_device *vdev, u16 idx)
> {
> struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
>
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> index c1c6431950e1..fe4d65aaf6aa 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> @@ -412,7 +412,7 @@ static u32 vdpasim_get_vq_align(struct vdpa_device *vdpa)
> return VDPASIM_QUEUE_ALIGN;
> }
>
> -static u32 vdpasim_get_vq_group(struct vdpa_device *vdpa, u16 idx)
> +static s64 vdpasim_get_vq_group(struct vdpa_device *vdpa, u16 idx)
> {
> /* RX and TX belongs to group 0, CVQ belongs to group 1 */
> if (idx == 2)
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index 2b6a8958ffe0..7ddd81456f7b 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -40,6 +40,7 @@
> #define DRV_LICENSE "GPL v2"
>
> #define VDUSE_DEV_MAX (1U << MINORBITS)
> +#define VDUSE_DEV_MAX_GROUPS 0xffff
> #define VDUSE_MAX_BOUNCE_SIZE (1024 * 1024 * 1024)
> #define VDUSE_MIN_BOUNCE_SIZE (1024 * 1024)
> #define VDUSE_BOUNCE_SIZE (64 * 1024 * 1024)
> @@ -49,6 +50,8 @@
>
> #define IRQ_UNBOUND -1
>
> +#define VQ_GROUP_INVALID -1
> +
> struct vduse_virtqueue {
> u16 index;
> u16 num_max;
> @@ -59,6 +62,7 @@ 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;
> @@ -115,6 +119,7 @@ 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;
> @@ -456,6 +461,7 @@ static void vduse_dev_reset(struct vduse_dev *dev)
> vq->driver_addr = 0;
> vq->device_addr = 0;
> vq->num = 0;
> + vq->vq_group = VQ_GROUP_INVALID;
> memset(&vq->state, 0, sizeof(vq->state));
>
> spin_lock(&vq->kick_lock);
> @@ -593,6 +599,19 @@ static int vduse_vdpa_set_vq_state(struct vdpa_device *vdpa, u16 idx,
> return 0;
> }
>
> +static s64 vduse_get_vq_group(struct vdpa_device *vdpa, u16 idx)
> +{
> + struct vduse_dev *dev = vdpa_to_vduse(vdpa);
> +
> + if (dev->api_version < VDUSE_API_VERSION_1)
> + return 0;
> +
> + if (dev->vqs[idx]->vq_group == VQ_GROUP_INVALID)
> + return -EINVAL;
> +
> + return dev->vqs[idx]->vq_group;
> +}
> +
> static int vduse_vdpa_get_vq_state(struct vdpa_device *vdpa, u16 idx,
> struct vdpa_vq_state *state)
> {
> @@ -790,6 +809,7 @@ 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,
> @@ -1253,12 +1273,24 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> if (config.index >= dev->vq_num)
> break;
>
> - if (!is_mem_zero((const char *)config.reserved,
> - sizeof(config.reserved)))
> + if (dev->api_version < VDUSE_API_VERSION_1 && config.group)
> + break;
> +
> + if (dev->api_version >= VDUSE_API_VERSION_1) {
> + if (config.group > dev->ngroups)
> + break;
> + if (dev->status & VIRTIO_CONFIG_S_DRIVER_OK)
> + break;

This seems to be a new requirement for V1. Please explain why.

> + }
> +
> + if (config.reserved1 ||
> + !is_mem_zero((const char *)config.reserved2,
> + sizeof(config.reserved2)))
> break;
>
> index = array_index_nospec(config.index, dev->vq_num);
> dev->vqs[index]->num_max = config.max_size;
> + dev->vqs[index]->vq_group = config.group;
> ret = 0;
> break;
> }
> @@ -1738,12 +1770,20 @@ 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 > VDUSE_DEV_MAX_GROUPS)
> + return false;
> +
> if (config->vq_align > PAGE_SIZE)
> return false;
>
> @@ -1859,6 +1899,7 @@ 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);

Should we fail if config->ngroups is zero when version is 1?

> dev->name = kstrdup(config->name, GFP_KERNEL);
> if (!dev->name)
> goto err_str;
> @@ -1937,7 +1978,7 @@ 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);
> @@ -2018,7 +2059,7 @@ 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/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 05a481e4c385..6305382eacbb 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -22,6 +22,7 @@
> #include <linux/vdpa.h>
> #include <linux/nospec.h>
> #include <linux/vhost.h>
> +#include <linux/types.h>
>
> #include "vhost.h"
>
> @@ -657,16 +658,20 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
> return -EFAULT;
> ops->set_vq_ready(vdpa, idx, s.num);
> return 0;
> - case VHOST_VDPA_GET_VRING_GROUP:
> + case VHOST_VDPA_GET_VRING_GROUP: {
> + u64 group;
> +
> if (!ops->get_vq_group)
> return -EOPNOTSUPP;
> s.index = idx;
> - s.num = ops->get_vq_group(vdpa, idx);
> - if (s.num >= vdpa->ngroups)
> + group = ops->get_vq_group(vdpa, idx);
> + if (group >= vdpa->ngroups || group > U32_MAX || group < 0)
> return -EIO;
> else if (copy_to_user(argp, &s, sizeof(s)))
> return -EFAULT;
> + s.num = group;
> return 0;
> + }
> case VHOST_VDPA_GET_VRING_DESC_GROUP:
> if (!vhost_vdpa_has_desc_group(v))
> return -EOPNOTSUPP;
> diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
> index 4cf21d6e9cfd..76a673ef7deb 100644
> --- a/include/linux/vdpa.h
> +++ b/include/linux/vdpa.h
> @@ -211,7 +211,8 @@ struct vdpa_map_file {
> * virtqueue (optional)
> * @vdev: vdpa device
> * @idx: virtqueue index
> - * Returns u32: group id for this virtqueue
> + * Returns i64: (32 bits wide) group id for this

Let's separate the u32->s64 changes. And maybe it's fine to say
returns s64 and explain U32_MAX is the maximum value allowed.

> + * virtqueue if >0. If <0, errno.
> * @get_vq_desc_group: Get the group id for the descriptor table of
> * a specific virtqueue (optional)
> * @vdev: vdpa device
> @@ -398,7 +399,7 @@ struct vdpa_config_ops {
>
> /* Device ops */
> u32 (*get_vq_align)(struct vdpa_device *vdev);
> - u32 (*get_vq_group)(struct vdpa_device *vdev, u16 idx);
> + s64 (*get_vq_group)(struct vdpa_device *vdev, u16 idx);
> u32 (*get_vq_desc_group)(struct vdpa_device *vdev, u16 idx);
> u64 (*get_device_features)(struct vdpa_device *vdev);
> u64 (*get_backend_features)(const struct vdpa_device *vdev);
> diff --git a/include/uapi/linux/vduse.h b/include/uapi/linux/vduse.h
> index ccb92a1efce0..a3d51cf6df3a 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[];
> };
> @@ -122,14 +124,18 @@ struct vduse_config_data {
> * struct vduse_vq_config - basic configuration of a virtqueue
> * @index: virtqueue index
> * @max_size: the max size of virtqueue
> - * @reserved: for future use, needs to be initialized to zero
> + * @reserved1: for future use, needs to be initialized to zero
> + * @group: virtqueue group
> + * @reserved2: for future use, needs to be initialized to zero
> *
> * Structure used by VDUSE_VQ_SETUP ioctl to setup a virtqueue.
> */
> struct vduse_vq_config {
> __u32 index;
> __u16 max_size;
> - __u16 reserved[13];
> + __u16 reserved1;
> + __u32 group;
> + __u16 reserved2[10];
> };
>
> /*
> --
> 2.51.0
>

Thanks