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

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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



It will be used in VDUSE case later.

Suggested-by: Jason Wang <jasowang@xxxxxxxxxx>
Signed-off-by: Xie Yongji <xieyongji@xxxxxxxxxxxxx>
---
  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.


  	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().


+
+	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?



+			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.

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


+		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.


/* 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)

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

Thanks


+
  struct vhost_iotlb_map {
  	struct rb_node rb;
  	struct list_head link;
@@ -17,6 +22,7 @@ struct vhost_iotlb_map {
  	u32 perm;
  	u32 flags_padding;
  	u64 __subtree_last;
+	void *opaque;
  };
#define VHOST_IOTLB_FLAG_RETIRE 0x1
@@ -30,7 +36,7 @@ struct vhost_iotlb {
  };
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);
  void vhost_iotlb_del_range(struct vhost_iotlb *iotlb, u64 start, u64 last);
struct vhost_iotlb *vhost_iotlb_alloc(unsigned int limit, unsigned int flags);




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