On Thu, Jan 15, 2026 at 9:41 AM Jason Wang <[email protected]> wrote:
>
> On Thu, Jan 15, 2026 at 2:49 AM Eugenio Pérez <[email protected]> wrote:
> >
> > Add support for assigning Address Space Identifiers (ASIDs) to each VQ
> > group. This enables mapping each group into a distinct memory space.
> >
> > The vq group to ASID association is protected by a rwlock now. But the
> > mutex domain_lock keeps protecting the domains of all ASIDs, as some
> > operations like the one related with the bounce buffer size still
> > requires to lock all the ASIDs.
> >
> > Signed-off-by: Eugenio Pérez <[email protected]>
> >
> > ---
> > Future improvements can include performance optimizations on top like
> > ore to RCU or thread synchronized atomics, or hardening by tracking ASID
> > or ASID hashes on unused bits of the DMA address.
> >
> > Tested virtio_vdpa by adding manually two threads in vduse_set_status:
> > one of them modifies the vq group 0 ASID and the other one map and unmap
> > memory continuously. After a while, the two threads stop and the usual
> > work continues. Test with version 0, version 1 with the old ioctl, and
> > version 1 with the new ioctl.
> >
> > Tested with vhost_vdpa by migrating a VM while ping on OVS+VDUSE. A few
> > workaround were needed in some parts:
> > * Do not enable CVQ before data vqs in QEMU, as VDUSE does not forward
> > the enable message to the userland device. This will be solved in the
> > future.
> > * Share the suspended state between all vhost devices in QEMU:
> > https://lists.nongnu.org/archive/html/qemu-devel/2025-11/msg02947.html
> > * Implement a fake VDUSE suspend vdpa operation callback that always
> > returns true in the kernel. DPDK suspend the device at the first
> > GET_VRING_BASE.
> > * Remove the CVQ blocker in ASID.
> >
> > The driver vhost_vdpa was also tested with version 0, version 1 with the
> > old ioctl, version 1 with the new ioctl but only one ASID, and version 1
> > with many ASID.
> >
> > ---
> > v12:
> > * Using scoped guards for vq group rwlock, so the one queue optimization
> > is not missed (Jason proposed to factor them into helpers).
> > * Add the _v2 suffix to vduse_iova_range_v2 struct name fixing the doc
> > (MST).
> > * s/verion/version/ in patch message.
> > * Remove trailing ; after a comment (Jason).
> >
> > v11:
> > * Remove duplicated free_pages_exact in vduse_domain_free_coherent
> > (Jason).
> > * Do not take the vq groups lock if nas == 1.
> > * Do not reset the vq group ASID in vq reset (Jason). Removed extra
> > function vduse_set_group_asid_nomsg, not needed anymore.
> > * Move the vduse_iotlb_entry_v2 argument to a new ioctl, as argument
> > didn't match the previous VDUSE_IOTLB_GET_FD.
> > * Move the asid < dev->nas check to vdpa core.
> >
> > v10:
> > * Back to rwlock version so stronger locks are used.
> > * Take out allocations from rwlock.
> > * Forbid changing ASID of a vq group after DRIVER_OK (Jason)
> > * Remove bad fetching again of domain variable in
> > vduse_dev_max_mapping_size (Yongji).
> > * Remove unused vdev definition in vdpa map_ops callbacks (kernel test
> > robot).
> >
> > v9:
> > * Replace mutex with rwlock, as the vdpa map_ops can run from atomic
> > context.
> >
> > v8:
> > * Revert the mutex to rwlock change, it needs proper profiling to
> > justify it.
> >
> > v7:
> > * Take write lock in the error path (Jason).
> >
> > v6:
> > * Make vdpa_dev_add use gotos for error handling (MST).
> > * s/(dev->api_version < 1) ?/(dev->api_version < VDUSE_API_VERSION_1) ?/
> > (MST).
> > * Fix struct name not matching in the doc.
> >
> > v5:
> > * Properly return errno if copy_to_user returns >0 in VDUSE_IOTLB_GET_FD
> > ioctl (Jason).
> > * Properly set domain bounce size to divide equally between nas (Jason).
> > * Exclude "padding" member from the only >V1 members in
> > vduse_dev_request.
> >
> > v4:
> > * Divide each domain bounce size between the device bounce size (Jason).
> > * revert unneeded addr = NULL assignment (Jason)
> > * Change if (x && (y || z)) return to if (x) { if (y) return; if (z)
> > return; } (Jason)
> > * Change a bad multiline comment, using @ caracter instead of * (Jason).
> > * Consider config->nas == 0 as a fail (Jason).
> >
> > v3:
> > * Get the vduse domain through the vduse_as in the map functions
> > (Jason).
> > * Squash with the patch creating the vduse_as struct (Jason).
> > * Create VDUSE_DEV_MAX_AS instead of comparing agains a magic number
> > (Jason)
> >
> > v2:
> > * Convert the use of mutex to rwlock.
> >
> > 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 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.
> >
> > RFC 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 | 385 +++++++++++++++++++----------
> > include/uapi/linux/vduse.h | 63 ++++-
> > 2 files changed, 312 insertions(+), 136 deletions(-)
> >
> > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c
> > b/drivers/vdpa/vdpa_user/vduse_dev.c
> > index d658f3e1cebf..2727c0c26003 100644
> > --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> > @@ -9,6 +9,7 @@
> > */
> >
> > #include "linux/virtio_net.h"
> > +#include <linux/cleanup.h>
> > #include <linux/init.h>
> > #include <linux/module.h>
> > #include <linux/cdev.h>
> > @@ -41,6 +42,7 @@
> >
> > #define VDUSE_DEV_MAX (1U << MINORBITS)
> > #define VDUSE_DEV_MAX_GROUPS 0xffff
> > +#define VDUSE_DEV_MAX_AS 0xffff
> > #define VDUSE_MAX_BOUNCE_SIZE (1024 * 1024 * 1024)
> > #define VDUSE_MIN_BOUNCE_SIZE (1024 * 1024)
> > #define VDUSE_BOUNCE_SIZE (64 * 1024 * 1024)
> > @@ -86,7 +88,15 @@ struct vduse_umem {
> > struct mm_struct *mm;
> > };
> >
> > +struct vduse_as {
> > + struct vduse_iova_domain *domain;
> > + struct vduse_umem *umem;
> > + struct mutex mem_lock;
> > +};
> > +
> > struct vduse_vq_group {
> > + rwlock_t as_lock;
> > + struct vduse_as *as; /* Protected by as_lock */
> > struct vduse_dev *dev;
> > };
> >
> > @@ -94,7 +104,7 @@ struct vduse_dev {
> > struct vduse_vdpa *vdev;
> > struct device *dev;
> > struct vduse_virtqueue **vqs;
> > - struct vduse_iova_domain *domain;
> > + struct vduse_as *as;
> > char *name;
> > struct mutex lock;
> > spinlock_t msg_lock;
> > @@ -122,9 +132,8 @@ struct vduse_dev {
> > u32 vq_num;
> > u32 vq_align;
> > u32 ngroups;
> > - struct vduse_umem *umem;
> > + u32 nas;
> > struct vduse_vq_group *groups;
> > - struct mutex mem_lock;
> > unsigned int bounce_size;
> > struct mutex domain_lock;
> > };
> > @@ -314,7 +323,7 @@ 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 };
> > @@ -323,8 +332,14 @@ 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);
> > }
> > @@ -439,11 +454,14 @@ static __poll_t vduse_dev_poll(struct file *file,
> > poll_table *wait)
> > static void vduse_dev_reset(struct vduse_dev *dev)
> > {
> > int i;
> > - struct vduse_iova_domain *domain = dev->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);
> > + }
> >
> > down_write(&dev->rwsem);
> >
> > @@ -622,6 +640,42 @@ static union virtio_map vduse_get_vq_map(struct
> > vdpa_device *vdpa, u16 idx)
> > return ret;
> > }
> >
> > +DEFINE_GUARD(vq_group_as_read_lock, struct vduse_vq_group *,
> > + if (_T->dev->nas > 1)
> > + read_lock(&_T->as_lock),
> > + if (_T->dev->nas > 1)
> > + read_unlock(&_T->as_lock))
> > +
> > +DEFINE_GUARD(vq_group_as_write_lock, struct vduse_vq_group *,
> > + if (_T->dev->nas > 1)
> > + write_lock(&_T->as_lock),
> > + if (_T->dev->nas > 1)
> > + write_unlock(&_T->as_lock))
> > +
> > +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)
> > + 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;
> > +
> > + guard(vq_group_as_write_lock)(&dev->groups[group]);
> > + dev->groups[group].as = &dev->as[asid];
> > +
> > + return 0;
> > +}
> > +
> > static int vduse_vdpa_get_vq_state(struct vdpa_device *vdpa, u16 idx,
> > struct vdpa_vq_state *state)
> > {
> > @@ -793,13 +847,13 @@ 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->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->domain, iotlb);
> > + vduse_domain_clear_map(dev->as[asid].domain, iotlb);
> > return ret;
> > }
> >
> > @@ -842,6 +896,7 @@ 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,
> > };
> > @@ -850,15 +905,13 @@ static void vduse_dev_sync_single_for_device(union
> > virtio_map token,
> > dma_addr_t dma_addr, size_t
> > size,
> > enum dma_data_direction dir)
> > {
> > - struct vduse_dev *vdev;
> > struct vduse_iova_domain *domain;
> >
> > if (!token.group)
> > return;
> >
> > - vdev = token.group->dev;
> > - domain = vdev->domain;
> > -
> > + guard(vq_group_as_read_lock)(token.group);
> > + domain = token.group->as->domain;
> > vduse_domain_sync_single_for_device(domain, dma_addr, size, dir);
> > }
> >
> > @@ -866,15 +919,13 @@ static void vduse_dev_sync_single_for_cpu(union
> > virtio_map token,
> > dma_addr_t dma_addr, size_t
> > size,
> > enum dma_data_direction dir)
> > {
> > - struct vduse_dev *vdev;
> > struct vduse_iova_domain *domain;
> >
> > if (!token.group)
> > return;
> >
> > - vdev = token.group->dev;
> > - domain = vdev->domain;
> > -
> > + guard(vq_group_as_read_lock)(token.group);
> > + domain = token.group->as->domain;
> > vduse_domain_sync_single_for_cpu(domain, dma_addr, size, dir);
> > }
> >
> > @@ -883,15 +934,13 @@ static dma_addr_t vduse_dev_map_page(union virtio_map
> > token, struct page *page,
> > enum dma_data_direction dir,
> > unsigned long attrs)
> > {
> > - struct vduse_dev *vdev;
> > struct vduse_iova_domain *domain;
> >
> > if (!token.group)
> > return DMA_MAPPING_ERROR;
> >
> > - vdev = token.group->dev;
> > - domain = vdev->domain;
> > -
> > + guard(vq_group_as_read_lock)(token.group);
> > + domain = token.group->as->domain;
> > return vduse_domain_map_page(domain, page, offset, size, dir,
> > attrs);
> > }
> >
> > @@ -899,23 +948,19 @@ static void vduse_dev_unmap_page(union virtio_map
> > token, dma_addr_t dma_addr,
> > size_t size, enum dma_data_direction dir,
> > unsigned long attrs)
> > {
> > - struct vduse_dev *vdev;
> > struct vduse_iova_domain *domain;
> >
> > if (!token.group)
> > return;
> >
> > - vdev = token.group->dev;
> > - domain = vdev->domain;
> > -
> > - return vduse_domain_unmap_page(domain, dma_addr, size, dir, attrs);
> > + guard(vq_group_as_read_lock)(token.group);
> > + domain = token.group->as->domain;
> > + vduse_domain_unmap_page(domain, dma_addr, size, dir, attrs);
> > }
> >
> > static void *vduse_dev_alloc_coherent(union virtio_map token, size_t size,
> > dma_addr_t *dma_addr, gfp_t flag)
> > {
> > - struct vduse_dev *vdev;
> > - struct vduse_iova_domain *domain;
> > void *addr;
> >
> > *dma_addr = DMA_MAPPING_ERROR;
> > @@ -926,11 +971,15 @@ static void *vduse_dev_alloc_coherent(union
> > virtio_map token, size_t size,
> > if (!addr)
> > return NULL;
> >
> > - vdev = token.group->dev;
> > - domain = vdev->domain;
> > - *dma_addr = vduse_domain_alloc_coherent(domain, size, addr);
> > - if (*dma_addr == DMA_MAPPING_ERROR)
> > - goto err;
> > + {
> > + struct vduse_iova_domain *domain;
> > +
> > + guard(vq_group_as_read_lock)(token.group);
> > + domain = token.group->as->domain;
> > + *dma_addr = vduse_domain_alloc_coherent(domain, size, addr);
> > + if (*dma_addr == DMA_MAPPING_ERROR)
> > + goto err;
> > + }
>
> Nit: Having a standalone block probably means we have the chance to
> optimize the code, maybe using a helper?
>
What do you mean by optimize the code? Would you prefer
vduse_dev_alloc_coherent function to be changed like this (untested)?
diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c
b/drivers/vdpa/vdpa_user/vduse_dev.c
index d658f3e1cebf..3561d3c00c89 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -911,11 +911,19 @@ static void vduse_dev_unmap_page(union
virtio_map token, dma_addr_t dma_addr,
return vduse_domain_unmap_page(domain, dma_addr, size, dir, attrs);
}
+static dma_addr_t *vduse_vq_group_alloc_coherent(struct vduse_vq_group *group,
+ size_t size, void *addr)
+{
+ struct vduse_iova_domain *domain;
+
+ guard(vq_group_as_read_lock)(token.group);
+ domain = token.group->as->domain;
+ return vduse_domain_alloc_coherent(domain, size, addr);
+}
+
static void *vduse_dev_alloc_coherent(union virtio_map token, size_t size,
dma_addr_t *dma_addr, gfp_t flag)
{
- struct vduse_dev *vdev;
- struct vduse_iova_domain *domain;
void *addr;
*dma_addr = DMA_MAPPING_ERROR;
@@ -926,9 +934,7 @@ static void *vduse_dev_alloc_coherent(union
virtio_map token, size_t size,
if (!addr)
return NULL;
- vdev = token.group->dev;
- domain = vdev->domain;
- *dma_addr = vduse_domain_alloc_coherent(domain, size, addr);
+ *dma_addr = vduse_vq_group_alloc_coherent(token.group, size, addr);
if (*dma_addr == DMA_MAPPING_ERROR)
goto err;
---
I don't love single use functions but I'm ok with the change if that's
what you want.
