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Message-ID: <CACGkMEv+FxECjhxfEKjZJcqXKc=c7RogAk6wdptBymTvL0fz1Q@mail.gmail.com>
Date: Wed, 17 Sep 2025 16:36:46 +0800
From: Jason Wang <jasowang@...hat.com>
To: Eugenio Pérez <eperezma@...hat.com>
Cc: "Michael S . Tsirkin" <mst@...hat.com>, Stefano Garzarella <sgarzare@...hat.com>,
Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, linux-kernel@...r.kernel.org,
Maxime Coquelin <mcoqueli@...hat.com>, Yongji Xie <xieyongji@...edance.com>,
Cindy Lu <lulu@...hat.com>, Laurent Vivier <lvivier@...hat.com>, virtualization@...ts.linux.dev
Subject: Re: [PATCH v2 3/7] vduse: add vq group support
On Tue, Sep 16, 2025 at 9:08 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>
> ---
> 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 | 37 ++++++++++++++++++++++++++----
> include/uapi/linux/vduse.h | 12 +++++++---
> 2 files changed, 41 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index 2b6a8958ffe0..42f8807911d4 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -59,6 +59,7 @@ 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 +116,7 @@ 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;
> @@ -593,6 +595,13 @@ 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;
I wonder if we should fail if VDUSE_VQ_SETUP is not set by userspace?
> +}
> +
> static int vduse_vdpa_get_vq_state(struct vdpa_device *vdpa, u16 idx,
> struct vdpa_vq_state *state)
> {
> @@ -790,6 +799,7 @@ 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 +1263,21 @@ 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 &&
> + config.group > dev->ngroups)
> + break;
> +
> + if (config.reserved1 ||
> + !is_mem_zero((const char *)config.reserved2,
> + sizeof(config.reserved2)))
> break;
What's the reason for having this check? I mean if we don't check this
since the day0, it might be too late to do that.
>
> 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 +1757,19 @@ 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;
Better with ngroups > 1?
> +
> + if (api_version >= VDUSE_API_VERSION_1 && config->ngroups > 0xffff)
> + return false;
> +
> if (config->vq_align > PAGE_SIZE)
> return false;
>
> @@ -1859,6 +1885,7 @@ 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;
> @@ -1937,7 +1964,7 @@ 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 +2045,7 @@ 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 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;
This makes me think if u16 is sufficient as I see:
u32 (*get_vq_group)(struct vdpa_device *vdev, u16 idx);
The index is u16 but the group is u32 ...
> + __u16 reserved2[10];
> };
>
> /*
> --
> 2.51.0
>
Thanks
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