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Message-ID: <CACycT3v=_Nm6fefJGFEyoU+Xf5G=Kzi0sXhhaBHnJQZcG-4EqA@mail.gmail.com>
Date: Mon, 8 Sep 2025 20:12:20 +0800
From: Yongji Xie <xieyongji@...edance.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 <linux-kernel@...r.kernel.org>, Jason Wang <jasowang@...hat.com>,
Maxime Coquelin <mcoqueli@...hat.com>
Subject: Re: [PATCH 5/6] vduse: add vq group asid support
Hi Eugenio,
On Tue, Aug 26, 2025 at 7:27 PM Eugenio Pérez <eperezma@...hat.com> wrote:
>
> Add support for assigning Address Space Identifiers (ASIDs) to each VQ
> group. This enables mapping each group into a distinct memory space.
>
> Now that the driver can change ASID in the middle of operation, the
> domain that each vq address point is also protected by domain_lock.
>
> Signed-off-by: Eugenio Pérez <eperezma@...hat.com>
> ---
> 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 TODO about merging VDUSE_IOTLB_GET_FD ioctl with
> VDUSE_IOTLB_GET_INFO.
> * Use of array_index_nospec in VDUSE device ioctls.
> * Embed vduse_iotlb_entry into vduse_iotlb_entry_v2.
> * Move the umem mutex to asid struct so there is no contention between
> ASIDs.
>
> v2:
> * Make iotlb entry the last one of vduse_iotlb_entry_v2 so the first
> part of the struct is the same.
> ---
> drivers/vdpa/vdpa_user/vduse_dev.c | 290 +++++++++++++++++++++--------
> include/uapi/linux/vduse.h | 52 +++++-
> 2 files changed, 259 insertions(+), 83 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index 7d2a3ed77b1e..2fb227713972 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -92,6 +92,7 @@ struct vduse_as {
> };
>
> struct vduse_vq_group_int {
> + struct vduse_iova_domain *domain;
> struct vduse_dev *dev;
> };
>
> @@ -99,7 +100,7 @@ struct vduse_dev {
> struct vduse_vdpa *vdev;
> struct device *dev;
> struct vduse_virtqueue **vqs;
> - struct vduse_as as;
> + struct vduse_as *as;
> char *name;
> struct mutex lock;
> spinlock_t msg_lock;
> @@ -127,6 +128,7 @@ struct vduse_dev {
> u32 vq_num;
> u32 vq_align;
> u32 ngroups;
> + u32 nas;
> struct vduse_vq_group_int *groups;
> unsigned int bounce_size;
> struct mutex domain_lock;
> @@ -317,7 +319,7 @@ static int vduse_dev_set_status(struct vduse_dev *dev, u8 status)
> return vduse_dev_msg_sync(dev, &msg);
> }
>
> -static int vduse_dev_update_iotlb(struct vduse_dev *dev,
> +static int vduse_dev_update_iotlb(struct vduse_dev *dev, u32 asid,
> u64 start, u64 last)
> {
> struct vduse_dev_msg msg = { 0 };
> @@ -326,8 +328,14 @@ static int vduse_dev_update_iotlb(struct vduse_dev *dev,
> return -EINVAL;
>
> msg.req.type = VDUSE_UPDATE_IOTLB;
> - msg.req.iova.start = start;
> - msg.req.iova.last = last;
> + if (dev->api_version < VDUSE_API_VERSION_1) {
> + msg.req.iova.start = start;
> + msg.req.iova.last = last;
> + } else {
> + msg.req.iova_v2.start = start;
> + msg.req.iova_v2.last = last;
> + msg.req.iova_v2.asid = asid;
> + }
>
> return vduse_dev_msg_sync(dev, &msg);
> }
> @@ -439,14 +447,28 @@ static __poll_t vduse_dev_poll(struct file *file, poll_table *wait)
> return mask;
> }
>
> +/* Force set the asid to a vq group without a message to the VDUSE device */
> +static void vduse_set_group_asid_nomsg(struct vduse_dev *dev,
> + unsigned int group, unsigned int asid)
> +{
> + guard(mutex)(&dev->domain_lock);
> + dev->groups[group].domain = dev->as[asid].domain;
> +}
> +
> static void vduse_dev_reset(struct vduse_dev *dev)
> {
> int i;
> - struct vduse_iova_domain *domain = dev->as.domain;
>
> /* The coherent mappings are handled in vduse_dev_free_coherent() */
> - if (domain && domain->bounce_map)
> - vduse_domain_reset_bounce_map(domain);
> + for (i = 0; i < dev->nas; i++) {
> + struct vduse_iova_domain *domain = dev->as[i].domain;
> +
> + if (domain && domain->bounce_map)
> + vduse_domain_reset_bounce_map(domain);
> + }
> +
> + for (i = 0; i < dev->ngroups; i++)
> + vduse_set_group_asid_nomsg(dev, i, 0);
>
> down_write(&dev->rwsem);
>
> @@ -620,6 +642,29 @@ static union virtio_map vduse_get_vq_map(struct vdpa_device *vdpa, u16 idx)
> return ret;
> }
>
> +static int vduse_set_group_asid(struct vdpa_device *vdpa, unsigned int group,
> + unsigned int asid)
> +{
> + struct vduse_dev *dev = vdpa_to_vduse(vdpa);
> + struct vduse_dev_msg msg = { 0 };
> + int r;
> +
> + if (dev->api_version < VDUSE_API_VERSION_1 ||
> + group >= dev->ngroups || asid >= dev->nas)
> + return -EINVAL;
> +
> + msg.req.type = VDUSE_SET_VQ_GROUP_ASID;
> + msg.req.vq_group_asid.group = group;
> + msg.req.vq_group_asid.asid = asid;
> +
> + r = vduse_dev_msg_sync(dev, &msg);
> + if (r < 0)
> + return r;
> +
> + vduse_set_group_asid_nomsg(dev, group, asid);
> + return 0;
> +}
> +
> static int vduse_vdpa_get_vq_state(struct vdpa_device *vdpa, u16 idx,
> struct vdpa_vq_state *state)
> {
> @@ -818,13 +863,13 @@ static int vduse_vdpa_set_map(struct vdpa_device *vdpa,
> struct vduse_dev *dev = vdpa_to_vduse(vdpa);
> int ret;
>
> - ret = vduse_domain_set_map(dev->as.domain, iotlb);
> + ret = vduse_domain_set_map(dev->as[asid].domain, iotlb);
> if (ret)
> return ret;
>
> - ret = vduse_dev_update_iotlb(dev, 0ULL, ULLONG_MAX);
> + ret = vduse_dev_update_iotlb(dev, asid, 0ULL, ULLONG_MAX);
> if (ret) {
> - vduse_domain_clear_map(dev->as.domain, iotlb);
> + vduse_domain_clear_map(dev->as[asid].domain, iotlb);
> return ret;
> }
>
> @@ -867,6 +912,7 @@ static const struct vdpa_config_ops vduse_vdpa_config_ops = {
> .get_vq_affinity = vduse_vdpa_get_vq_affinity,
> .reset = vduse_vdpa_reset,
> .set_map = vduse_vdpa_set_map,
> + .set_group_asid = vduse_set_group_asid,
> .get_vq_map = vduse_get_vq_map,
> .free = vduse_vdpa_free,
> };
> @@ -876,8 +922,10 @@ static void vduse_dev_sync_single_for_device(union virtio_map token,
> enum dma_data_direction dir)
> {
> struct vduse_dev *vdev = token.group->dev;
> - struct vduse_iova_domain *domain = vdev->as.domain;
> + struct vduse_iova_domain *domain;
>
> + guard(mutex)(&vdev->domain_lock);
> + domain = token.group->domain;
> vduse_domain_sync_single_for_device(domain, dma_addr, size, dir);
> }
>
> @@ -886,8 +934,10 @@ static void vduse_dev_sync_single_for_cpu(union virtio_map token,
> enum dma_data_direction dir)
> {
> struct vduse_dev *vdev = token.group->dev;
> - struct vduse_iova_domain *domain = vdev->as.domain;
> + struct vduse_iova_domain *domain;
>
> + guard(mutex)(&vdev->domain_lock);
> + domain = token.group->domain;
> vduse_domain_sync_single_for_cpu(domain, dma_addr, size, dir);
> }
>
> @@ -897,8 +947,10 @@ static dma_addr_t vduse_dev_map_page(union virtio_map token, struct page *page,
> unsigned long attrs)
> {
> struct vduse_dev *vdev = token.group->dev;
> - struct vduse_iova_domain *domain = vdev->as.domain;
> + struct vduse_iova_domain *domain;
>
> + guard(mutex)(&vdev->domain_lock);
Won't this mutex lock hurt the performance? Can we use rw_lock/rcu_lock instead?
Thanks,
Yongji
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