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Message-ID: <CAJaqyWfx8L6rt+sEeVjdPQ3y0=c_8gSi5_d1TLUopq5PmqAY9w@mail.gmail.com>
Date: Fri, 26 Sep 2025 10:15:20 +0200
From: Eugenio Perez Martin <eperezma@...hat.com>
To: Jason Wang <jasowang@...hat.com>
Cc: "Michael S . Tsirkin" <mst@...hat.com>, Yongji Xie <xieyongji@...edance.com>, Cindy Lu <lulu@...hat.com>,
linux-kernel@...r.kernel.org, Maxime Coquelin <mcoqueli@...hat.com>,
Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Laurent Vivier <lvivier@...hat.com>,
virtualization@...ts.linux.dev, Stefano Garzarella <sgarzare@...hat.com>
Subject: Re: [PATCH v4 3/6] vduse: add vq group support
On Fri, Sep 26, 2025 at 9:42 AM Jason Wang <jasowang@...hat.com> wrote:
>
> On Thu, Sep 25, 2025 at 5:14 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>
> > ---
> > v4:
> > * Revert the "invalid vq group" concept and assume 0 if not set (Jason).
> > * Make config->ngroups == 0 invalid (Jason).
> >
> > 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/vdpa_user/vduse_dev.c | 46 ++++++++++++++++++++++++++----
> > drivers/vhost/vdpa.c | 11 +++++--
> > include/uapi/linux/vduse.h | 12 ++++++--
> > 3 files changed, 58 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> > index 2b6a8958ffe0..3415217cb3a9 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)
> > @@ -59,6 +60,7 @@ 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 +117,7 @@ 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 +459,7 @@ static void vduse_dev_reset(struct vduse_dev *dev)
> > vq->driver_addr = 0;
> > vq->device_addr = 0;
> > vq->num = 0;
> > + vq->vq_group = 0;
> > memset(&vq->state, 0, sizeof(vq->state));
> >
> > spin_lock(&vq->kick_lock);
> > @@ -593,6 +597,16 @@ 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);
> > +
> > + if (dev->api_version < VDUSE_API_VERSION_1)
> > + return 0;
> > +
> > + 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 +804,7 @@ 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 +1268,24 @@ 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;
>
> This should be ">=".
>
Right, good catch!
> > + if (dev->status & VIRTIO_CONFIG_S_DRIVER_OK)
> > + break;
> > + }
> > +
> > + 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 +1765,20 @@ 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 || config->ngroups > VDUSE_DEV_MAX_GROUPS))
> > + return false;
> > +
> > if (config->vq_align > PAGE_SIZE)
> > return false;
> >
> > @@ -1859,6 +1894,7 @@ 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;
> > dev->name = kstrdup(config->name, GFP_KERNEL);
> > if (!dev->name)
> > goto err_str;
> > @@ -1937,7 +1973,7 @@ 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 +2054,7 @@ 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;
>
> I guess this won't work.
>
Right, and it has a lot of dead code from the s64 conversion. Fixing it.
Should I send the whole series again or a patch on top?
> > return 0;
> > + }
> > case VHOST_VDPA_GET_VRING_DESC_GROUP:
> > if (!vhost_vdpa_has_desc_group(v))
> > return -EOPNOTSUPP;
> > 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
>
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