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

[Yongji Xie <xieyongji@bytedance.com>]

On Wed, Jan 27, 2021 at 11:51 AM Jason Wang <jasowang@redhat.com> wrote:
>
>
> On 2021/1/20 下午3:52, Yongji Xie wrote:
> > 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?
>
>
> Probably not, we do something similar in virtio core:
>
> void *virtqueue_get_buf_ctx(struct virtqueue *_vq, unsigned int *len,
>                  void **ctx)
> {
>      struct vring_virtqueue *vq = to_vvq(_vq);
>
>      return vq->packed_ring ? virtqueue_get_buf_ctx_packed(_vq, len, ctx) :
>                   virtqueue_get_buf_ctx_split(_vq, len, ctx);
> }
> EXPORT_SYMBOL_GPL(virtqueue_get_buf_ctx);
>
> void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)
> {
>      return virtqueue_get_buf_ctx(_vq, len, NULL);
> }
> EXPORT_SYMBOL_GPL(virtqueue_get_buf);
>

I see. Will do it in the next version.

>
> >
> >>>        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?
>
>
> I meant do we need to allow VM_IO here? (We don't allow such case in
> vhost-vdpa now).
>

OK, let's exclude the vma with VM_IO | VM_PFNMAP.

>
> >
> > 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.
>
>
> Yes, e.g bios or other rom. Vhost-user has the similar issue and they
> filter the out them in qemu.
>
> For vhost-vDPA, consider it can supports various difference backends, we
> can't do that.
>

OK, I will transfer iotlb_file with NULL file and let the backend do
the filtering.

Thanks,
Yongji