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

[Yongji Xie <xieyongji@bytedance.com>]

On Wed, Jan 20, 2021 at 2:24 PM Jason Wang <jasowang@redhat.com> wrote:
>
>
> On 2021/1/19 下午12:59, Xie Yongji wrote:
> > 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.

>
> >
> > It will be used in VDUSE case later.
> >
> > Suggested-by: Jason Wang <jasowang@redhat.com>
> > Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> > ---
> >   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?

>
> >       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.

>
> > +
> > +     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.

>
>
> > +                     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.

>
> > +             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?

>
> >
> >       /* 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