Re: Re: [RFC v3 06/11] vhost-vdpa: Add an opaque pointer for vhost IOTLB

On Wed, Jan 20, 2021 at 2:24 PM Jason Wang [off-list ref] wrote:

On 2021/1/19 下午12:59, Xie Yongji wrote:

quoted

Add an opaque pointer for vhost IOTLB to store the
corresponding vma->vm_file and offset on the DMA mapping.

Let's split the patch into two.

1) opaque pointer
2) vma stuffs

OK.

quoted

It will be used in VDUSE case later.

Suggested-by: Jason Wang <redacted>
Signed-off-by: Xie Yongji <redacted>
---
  drivers/vdpa/vdpa_sim/vdpa_sim.c | 11 ++++---
  drivers/vhost/iotlb.c            |  5 ++-
  drivers/vhost/vdpa.c             | 66 +++++++++++++++++++++++++++++++++++-----
  drivers/vhost/vhost.c            |  4 +--
  include/linux/vdpa.h             |  3 +-
  include/linux/vhost_iotlb.h      |  8 ++++-
  6 files changed, 79 insertions(+), 18 deletions(-)

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index 03c796873a6b..1ffcef67954f 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c

@@ -279,7 +279,7 @@ static dma_addr_t vdpasim_map_page(struct device *dev, struct page *page,
       */
      spin_lock(&vdpasim->iommu_lock);
      ret = vhost_iotlb_add_range(iommu, pa, pa + size - 1,
-                                 pa, dir_to_perm(dir));
+                                 pa, dir_to_perm(dir), NULL);

Maybe its better to introduce

vhost_iotlb_add_range_ctx() which can accepts the opaque (context). And
let vhost_iotlb_add_range() just call that.

If so, we need export both vhost_iotlb_add_range() and
vhost_iotlb_add_range_ctx() which will be used in VDUSE driver. Is it
a bit redundant?

quoted

      spin_unlock(&vdpasim->iommu_lock);
      if (ret)
              return DMA_MAPPING_ERROR;

@@ -317,7 +317,7 @@ static void *vdpasim_alloc_coherent(struct device *dev, size_t size,

              ret = vhost_iotlb_add_range(iommu, (u64)pa,
                                          (u64)pa + size - 1,
-                                         pa, VHOST_MAP_RW);
+                                         pa, VHOST_MAP_RW, NULL);
              if (ret) {
                      *dma_addr = DMA_MAPPING_ERROR;
                      kfree(addr);

@@ -625,7 +625,8 @@ static int vdpasim_set_map(struct vdpa_device *vdpa,
      for (map = vhost_iotlb_itree_first(iotlb, start, last); map;
           map = vhost_iotlb_itree_next(map, start, last)) {
              ret = vhost_iotlb_add_range(vdpasim->iommu, map->start,
-                                         map->last, map->addr, map->perm);
+                                         map->last, map->addr,
+                                         map->perm, NULL);
              if (ret)
                      goto err;
      }

@@ -639,14 +640,14 @@ static int vdpasim_set_map(struct vdpa_device *vdpa,
  }

  static int vdpasim_dma_map(struct vdpa_device *vdpa, u64 iova, u64 size,
-                        u64 pa, u32 perm)
+                        u64 pa, u32 perm, void *opaque)
  {
      struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
      int ret;

      spin_lock(&vdpasim->iommu_lock);
      ret = vhost_iotlb_add_range(vdpasim->iommu, iova, iova + size - 1, pa,
-                                 perm);
+                                 perm, NULL);
      spin_unlock(&vdpasim->iommu_lock);

      return ret;

diff --git a/drivers/vhost/iotlb.c b/drivers/vhost/iotlb.c
index 0fd3f87e913c..3bd5bd06cdbc 100644
--- a/drivers/vhost/iotlb.c
+++ b/drivers/vhost/iotlb.c

@@ -42,13 +42,15 @@ EXPORT_SYMBOL_GPL(vhost_iotlb_map_free);
   * @last: last of IOVA range
   * @addr: the address that is mapped to @start
   * @perm: access permission of this range
+ * @opaque: the opaque pointer for the IOTLB mapping
   *
   * Returns an error last is smaller than start or memory allocation
   * fails
   */
  int vhost_iotlb_add_range(struct vhost_iotlb *iotlb,
                        u64 start, u64 last,
-                       u64 addr, unsigned int perm)
+                       u64 addr, unsigned int perm,
+                       void *opaque)
  {
      struct vhost_iotlb_map *map;

@@ -71,6 +73,7 @@ int vhost_iotlb_add_range(struct vhost_iotlb *iotlb,
      map->last = last;
      map->addr = addr;
      map->perm = perm;
+     map->opaque = opaque;

      iotlb->nmaps++;
      vhost_iotlb_itree_insert(map, &iotlb->root);

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 36b6950ba37f..e83e5be7cec8 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c

@@ -488,6 +488,7 @@ static void vhost_vdpa_iotlb_unmap(struct vhost_vdpa *v, u64 start, u64 last)
      struct vhost_dev *dev = &v->vdev;
      struct vdpa_device *vdpa = v->vdpa;
      struct vhost_iotlb *iotlb = dev->iotlb;
+     struct vhost_iotlb_file *iotlb_file;
      struct vhost_iotlb_map *map;
      struct page *page;
      unsigned long pfn, pinned;

@@ -504,6 +505,10 @@ static void vhost_vdpa_iotlb_unmap(struct vhost_vdpa *v, u64 start, u64 last)
                      }
                      atomic64_sub(map->size >> PAGE_SHIFT,
                                      &dev->mm->pinned_vm);
+             } else if (map->opaque) {
+                     iotlb_file = (struct vhost_iotlb_file *)map->opaque;
+                     fput(iotlb_file->file);
+                     kfree(iotlb_file);
              }
              vhost_iotlb_map_free(iotlb, map);
      }

@@ -540,8 +545,8 @@ static int perm_to_iommu_flags(u32 perm)
      return flags | IOMMU_CACHE;
  }

-static int vhost_vdpa_map(struct vhost_vdpa *v,
-                       u64 iova, u64 size, u64 pa, u32 perm)
+static int vhost_vdpa_map(struct vhost_vdpa *v, u64 iova,
+                       u64 size, u64 pa, u32 perm, void *opaque)
  {
      struct vhost_dev *dev = &v->vdev;
      struct vdpa_device *vdpa = v->vdpa;

@@ -549,12 +554,12 @@ static int vhost_vdpa_map(struct vhost_vdpa *v,
      int r = 0;

      r = vhost_iotlb_add_range(dev->iotlb, iova, iova + size - 1,
-                               pa, perm);
+                               pa, perm, opaque);
      if (r)
              return r;

      if (ops->dma_map) {
-             r = ops->dma_map(vdpa, iova, size, pa, perm);
+             r = ops->dma_map(vdpa, iova, size, pa, perm, opaque);
      } else if (ops->set_map) {
              if (!v->in_batch)
                      r = ops->set_map(vdpa, dev->iotlb);

@@ -591,6 +596,51 @@ static void vhost_vdpa_unmap(struct vhost_vdpa *v, u64 iova, u64 size)
      }
  }

+static int vhost_vdpa_sva_map(struct vhost_vdpa *v,
+                           u64 iova, u64 size, u64 uaddr, u32 perm)
+{
+     u64 offset, map_size, map_iova = iova;
+     struct vhost_iotlb_file *iotlb_file;
+     struct vm_area_struct *vma;
+     int ret;

Lacking mmap_read_lock().

Good catch! Will fix it.

quoted

+
+     while (size) {
+             vma = find_vma(current->mm, uaddr);
+             if (!vma) {
+                     ret = -EINVAL;
+                     goto err;
+             }
+             map_size = min(size, vma->vm_end - uaddr);
+             offset = (vma->vm_pgoff << PAGE_SHIFT) + uaddr - vma->vm_start;
+             iotlb_file = NULL;
+             if (vma->vm_file && (vma->vm_flags & VM_SHARED)) {

I wonder if we need more strict check here. When developing vhost-vdpa,
I try hard to make sure the map can only work for user pages.

So the question is: do we need to exclude MMIO area or only allow shmem
to work here?

Do you mean we need to check VM_MIXEDMAP | VM_PFNMAP here?

It makes sense to me.

quoted

+                     iotlb_file = kmalloc(sizeof(*iotlb_file), GFP_KERNEL);
+                     if (!iotlb_file) {
+                             ret = -ENOMEM;
+                             goto err;
+                     }
+                     iotlb_file->file = get_file(vma->vm_file);
+                     iotlb_file->offset = offset;
+             }

I wonder if it's better to allocate iotlb_file and make iotlb_file->file
= NULL && iotlb_file->offset = 0. This can force a consistent code for
the vDPA parents.

Looks fine to me.

Or we can simply fail the map without a file as backend.

Actually there will be some vma without vm_file during vm booting.

quoted

+             ret = vhost_vdpa_map(v, map_iova, map_size, uaddr,
+                                     perm, iotlb_file);
+             if (ret) {
+                     if (iotlb_file) {
+                             fput(iotlb_file->file);
+                             kfree(iotlb_file);
+                     }
+                     goto err;
+             }
+             size -= map_size;
+             uaddr += map_size;
+             map_iova += map_size;
+     }
+     return 0;
+err:
+     vhost_vdpa_unmap(v, iova, map_iova - iova);
+     return ret;
+}
+
  static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
                                         struct vhost_iotlb_msg *msg)
  {

@@ -615,8 +665,8 @@ static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
              return -EEXIST;

      if (vdpa->sva)
-             return vhost_vdpa_map(v, msg->iova, msg->size,
-                                   msg->uaddr, msg->perm);
+             return vhost_vdpa_sva_map(v, msg->iova, msg->size,
+                                       msg->uaddr, msg->perm);

So I think it's better squash vhost_vdpa_sva_map() and related changes
into previous patch.

OK, so the order of the patches is:
1) opaque pointer
2) va support + vma stuffs?

Is it OK?

quoted

      /* Limit the use of memory for bookkeeping */
      page_list = (struct page **) __get_free_page(GFP_KERNEL);

@@ -671,7 +721,7 @@ static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
                              csize = (last_pfn - map_pfn + 1) << PAGE_SHIFT;
                              ret = vhost_vdpa_map(v, iova, csize,
                                                   map_pfn << PAGE_SHIFT,
-                                                  msg->perm);
+                                                  msg->perm, NULL);
                              if (ret) {
                                      /*
                                       * Unpin the pages that are left unmapped

@@ -700,7 +750,7 @@ static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,

      /* Pin the rest chunk */
      ret = vhost_vdpa_map(v, iova, (last_pfn - map_pfn + 1) << PAGE_SHIFT,
-                          map_pfn << PAGE_SHIFT, msg->perm);
+                          map_pfn << PAGE_SHIFT, msg->perm, NULL);
  out:
      if (ret) {
              if (nchunks) {

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index a262e12c6dc2..120dd5b3c119 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c

@@ -1104,7 +1104,7 @@ static int vhost_process_iotlb_msg(struct vhost_dev *dev,
              vhost_vq_meta_reset(dev);
              if (vhost_iotlb_add_range(dev->iotlb, msg->iova,
                                        msg->iova + msg->size - 1,
-                                       msg->uaddr, msg->perm)) {
+                                       msg->uaddr, msg->perm, NULL)) {
                      ret = -ENOMEM;
                      break;
              }

@@ -1450,7 +1450,7 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
                                        region->guest_phys_addr +
                                        region->memory_size - 1,
                                        region->userspace_addr,
-                                       VHOST_MAP_RW))
+                                       VHOST_MAP_RW, NULL))
                      goto err;
      }

diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
index f86869651614..b264c627e94b 100644
--- a/include/linux/vdpa.h
+++ b/include/linux/vdpa.h

@@ -189,6 +189,7 @@ struct vdpa_iova_range {
   *                          @size: size of the area
   *                          @pa: physical address for the map
   *                          @perm: device access permission (VHOST_MAP_XX)
+ *                           @opaque: the opaque pointer for the mapping
   *                          Returns integer: success (0) or error (< 0)
   * @dma_unmap:                      Unmap an area of IOVA (optional but
   *                          must be implemented with dma_map)

@@ -243,7 +244,7 @@ struct vdpa_config_ops {
      /* DMA ops */
      int (*set_map)(struct vdpa_device *vdev, struct vhost_iotlb *iotlb);
      int (*dma_map)(struct vdpa_device *vdev, u64 iova, u64 size,
-                    u64 pa, u32 perm);
+                    u64 pa, u32 perm, void *opaque);
      int (*dma_unmap)(struct vdpa_device *vdev, u64 iova, u64 size);

      /* Free device resources */

diff --git a/include/linux/vhost_iotlb.h b/include/linux/vhost_iotlb.h
index 6b09b786a762..66a50c11c8ca 100644
--- a/include/linux/vhost_iotlb.h
+++ b/include/linux/vhost_iotlb.h

@@ -4,6 +4,11 @@

  #include <linux/interval_tree_generic.h>

+struct vhost_iotlb_file {
+     struct file *file;
+     u64 offset;
+};

I think we'd better either:

1) simply use struct vhost_iotlb_file * instead of void *opaque for
vhost_iotlb_map

or

2)rename and move the vhost_iotlb_file to vdpa

2) looks better since we want to let vhost iotlb to carry any type of
context (opaque pointer)

I agree. So we need to introduce struct vdpa_iotlb_file in
include/linux/vdpa.h, right?

And if we do this, the modification of vdpa_config_ops deserves a
separate patch.

Sorry, I didn't get you here. What do you mean by the modification of
vdpa_config_ops? Do you mean adding an opaque pointer to ops.dma_map?

Thanks,
Yongji