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Date: Wed, 27 Jan 2021 11:51:04 +0800
From: Jason Wang <jasowang@...hat.com>
To: Yongji Xie <xieyongji@...edance.com>
Cc: "Michael S. Tsirkin" <mst@...hat.com>,
Stefan Hajnoczi <stefanha@...hat.com>, sgarzare@...hat.com,
Parav Pandit <parav@...dia.com>, Bob Liu <bob.liu@...cle.com>,
Christoph Hellwig <hch@...radead.org>,
Randy Dunlap <rdunlap@...radead.org>,
Matthew Wilcox <willy@...radead.org>, viro@...iv.linux.org.uk,
axboe@...nel.dk, bcrl@...ck.org, Jonathan Corbet <corbet@....net>,
virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
kvm@...r.kernel.org, linux-aio@...ck.org,
linux-fsdevel@...r.kernel.org
Subject: Re: [RFC v3 06/11] vhost-vdpa: Add an opaque pointer for vhost IOTLB
On 2021/1/20 下午3:52, Yongji Xie wrote:
> On Wed, Jan 20, 2021 at 2:24 PM Jason Wang <jasowang@...hat.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@...hat.com>
>>> Signed-off-by: Xie Yongji <xieyongji@...edance.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
>
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