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Message-ID: <CACGkMEuGC6NQmfUgXj1YVyURQ6-S2YT2qkAuYQGLpqVaV75kJg@mail.gmail.com>
Date: Mon, 9 Jun 2025 09:55:13 +0800
From: Jason Wang <jasowang@...hat.com>
To: Eugenio Pérez <eperezma@...hat.com>
Cc: Yongji Xie <xieyongji@...edance.com>, Cindy Lu <lulu@...hat.com>,
linux-kernel@...r.kernel.org, Stefano Garzarella <sgarzare@...hat.com>,
Stefan Hajnoczi <stefanha@...hat.com>, Maxime Coquelin <mcoqueli@...hat.com>,
"Michael S. Tsirkin" <mst@...hat.com>, virtualization@...ts.linux.dev,
Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Laurent Vivier <lvivier@...hat.com>
Subject: Re: [RFC 2/6] vduse: add vq group support
On Fri, Jun 6, 2025 at 7:50 PM Eugenio Pérez <eperezma@...hat.com> wrote:
>
> The virtqueue group is the minimal set of virtqueues that must share an
> address space. And the address space identifier could only be attached
> to a specific virtqueue group. The virtqueue is attached to a
> virtqueue group for all the life of the device.
>
> During vDPA device allocation, the VDUSE device needs to report the
> number of virtqueue groups supported. At this moment only vhost_vdpa is
> able to do it.
>
> This helps to isolate the environments for the virtqueue that will not
> be assigned directly. E.g in the case of virtio-net, the control
> virtqueue will not be assigned directly to guest.
>
> As we need to back the vq groups with a struct device for the file
> operations, let's keep this number as low as possible at the moment: 2.
> We can back one VQ group with the vduse device and the other one with
> the vdpa device.
>
> Signed-off-by: Eugenio Pérez <eperezma@...hat.com>
> ---
> drivers/vdpa/vdpa_user/vduse_dev.c | 44 +++++++++++++++++++++++++++++-
> include/uapi/linux/vduse.h | 17 +++++++++++-
> 2 files changed, 59 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index 6a9a37351310..6fa687bc4912 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -46,6 +46,11 @@
> #define VDUSE_IOVA_SIZE (VDUSE_MAX_BOUNCE_SIZE + 128 * 1024 * 1024)
> #define VDUSE_MSG_DEFAULT_TIMEOUT 30
>
> +/*
> + * Let's make it 2 for simplicity.
> + */
> +#define VDUSE_MAX_VQ_GROUPS 2
> +
> #define IRQ_UNBOUND -1
>
> struct vduse_virtqueue {
> @@ -114,6 +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;
> @@ -592,6 +598,25 @@ 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);
> + struct vduse_dev_msg msg = { 0 };
> + int ret;
> +
> + if (dev->api_version < VDUSE_API_VERSION_1)
> + return 0;
> +
> + msg.req.type = VDUSE_GET_VQ_GROUP;
> + msg.req.vq_group.index = idx;
Considering there will be a set_group_asid request, could the kernel
cache the result so we don't need to bother with requests from
userspace?
> +
> + ret = vduse_dev_msg_sync(dev, &msg);
> + if (ret)
> + return ret;
> +
> + return msg.resp.vq_group.num;
> +}
> +
> static int vduse_vdpa_get_vq_state(struct vdpa_device *vdpa, u16 idx,
> struct vdpa_vq_state *state)
> {
> @@ -789,6 +814,7 @@ 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,
> @@ -1850,6 +1876,16 @@ 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;
> + if (dev->api_version >= 1) {
> + if (config->ngroups > VDUSE_MAX_VQ_GROUPS) {
> + pr_err("Not creating a VDUSE device with %u vq groups. Max: %u",
> + config->ngroups, VDUSE_MAX_VQ_GROUPS);
> + goto err_ngroups;
> + }
> + dev->ngroups = config->ngroups ?: 1;
> + } else {
> + dev->ngroups = 1;
> + }
> dev->name = kstrdup(config->name, GFP_KERNEL);
> if (!dev->name)
> goto err_str;
> @@ -1885,6 +1921,7 @@ static int vduse_create_dev(struct vduse_dev_config *config,
> idr_remove(&vduse_idr, dev->minor);
> err_idr:
> kfree(dev->name);
> +err_ngroups:
> err_str:
> vduse_dev_destroy(dev);
> err:
> @@ -2003,13 +2040,18 @@ static struct vduse_mgmt_dev *vduse_mgmt;
> static int vduse_dev_init_vdpa(struct vduse_dev *dev, const char *name)
> {
> struct vduse_vdpa *vdev;
> + __u32 ngroups = 1;
> int ret;
>
> if (dev->vdev)
> return -EEXIST;
>
> + if (vdev->dev->api_version >= VDUSE_API_VERSION_1)
> + ngroups = vdev->dev->ngroups;
> +
> vdev = vdpa_alloc_device(struct vduse_vdpa, vdpa, dev->dev,
> - &vduse_vdpa_config_ops, 1, 1, name, true);
> + &vduse_vdpa_config_ops, 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..a779bcddac58 100644
> --- a/include/uapi/linux/vduse.h
> +++ b/include/uapi/linux/vduse.h
> @@ -45,7 +45,8 @@ 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 +161,16 @@ struct vduse_vq_state_packed {
> __u16 last_used_idx;
> };
>
> +/**
> + * struct vduse_vq_group - virtqueue group
> + * @num: Index of the virtqueue group
> + * @num: Group
> + */
> +struct vduse_vq_group {
> + __u32 index;
> + __u32 num;
> +};
> +
> /**
> * struct vduse_vq_info - information of a virtqueue
> * @index: virtqueue index
> @@ -182,6 +193,7 @@ struct vduse_vq_info {
> union {
> struct vduse_vq_state_split split;
> struct vduse_vq_state_packed packed;
> + struct vduse_vq_group group;
> };
> __u8 ready;
> };
> @@ -274,6 +286,7 @@ enum vduse_req_type {
> VDUSE_GET_VQ_STATE,
> VDUSE_SET_STATUS,
> VDUSE_UPDATE_IOTLB,
> + VDUSE_GET_VQ_GROUP,
> };
>
> /**
> @@ -328,6 +341,7 @@ struct vduse_dev_request {
> struct vduse_vq_state vq_state;
> struct vduse_dev_status s;
> struct vduse_iova_range iova;
> + struct vduse_vq_group vq_group; /* Only if vduse api version >= 1 */
> __u32 padding[32];
This should be [31] otherwise we break the uAPI?
> };
> };
> @@ -350,6 +364,7 @@ struct vduse_dev_response {
> __u32 reserved[4];
> union {
> struct vduse_vq_state vq_state;
> + struct vduse_vq_group vq_group; /* Only if vduse api version >= 1 */
> __u32 padding[32];
And here?
Thanks
> };
> };
> --
> 2.49.0
>
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