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

[Jason Wang <jasowang@redhat.com>]

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);


>
>>>        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).


>
> 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.


>
>>> +             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?


Fine with me.


>
>>>        /* 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?


Yes.


>
>> 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?


Yes.

Thanks


>
> Thanks,
> Yongji
>