diff mbox series

[net-next,02/13] virtio_ring: split: harden dma unmap for indirect

Message ID 20240820073330.9161-3-xuanzhuo@linux.alibaba.com (mailing list archive)
State Changes Requested
Delegated to: Netdev Maintainers
Headers show
Series virtio-net: support AF_XDP zero copy (tx) | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 16 this patch: 16
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers success CCed 6 of 6 maintainers
netdev/build_clang success Errors and warnings before: 16 this patch: 16
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 16 this patch: 16
netdev/checkpatch warning WARNING: line length of 83 exceeds 80 columns WARNING: line length of 91 exceeds 80 columns
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 22 this patch: 22
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-08-20--15-00 (tests: 712)

Commit Message

Xuan Zhuo Aug. 20, 2024, 7:33 a.m. UTC 
1. this commit hardens dma unmap for indirect
2. the subsequent commit uses the struct extra to record whether the
   buffers need to be unmapped or not. So we need a struct extra for
   every desc, whatever it is indirect or not.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
 drivers/virtio/virtio_ring.c | 122 ++++++++++++++++-------------------
 1 file changed, 57 insertions(+), 65 deletions(-)

Comments

Jason Wang Sept. 11, 2024, 3:46 a.m. UTC | #1 
On Tue, Aug 20, 2024 at 3:33 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
>
> 1. this commit hardens dma unmap for indirect

I think we need to explain why we need such hardening. For example
indirect use stream mapping which is read-only from the device. So it
looks to me like it doesn't require hardening by itself.

> 2. the subsequent commit uses the struct extra to record whether the
>    buffers need to be unmapped or not.

It's better to explain why such a decision could not be implied with
the existing metadata.

>  So we need a struct extra for
>    every desc, whatever it is indirect or not.

If this is the real reason, we need to tweak the title.

>
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> ---
>  drivers/virtio/virtio_ring.c | 122 ++++++++++++++++-------------------
>  1 file changed, 57 insertions(+), 65 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 228e9fbcba3f..582d2c05498a 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -67,9 +67,16 @@
>  #define LAST_ADD_TIME_INVALID(vq)
>  #endif
>
> +struct vring_desc_extra {
> +       dma_addr_t addr;                /* Descriptor DMA addr. */
> +       u32 len;                        /* Descriptor length. */
> +       u16 flags;                      /* Descriptor flags. */
> +       u16 next;                       /* The next desc state in a list. */
> +};
> +
>  struct vring_desc_state_split {
>         void *data;                     /* Data for callback. */
> -       struct vring_desc *indir_desc;  /* Indirect descriptor, if any. */
> +       struct vring_desc_extra *indir; /* Indirect descriptor, if any. */

Btw, it might be worth explaining that this will be allocated with an
indirect descriptor table so we won't stress more to the memory
allocator.

Thanks
Michael S. Tsirkin Sept. 11, 2024, 10:30 a.m. UTC | #2 
On Wed, Sep 11, 2024 at 11:46:30AM +0800, Jason Wang wrote:
> On Tue, Aug 20, 2024 at 3:33 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
> >
> > 1. this commit hardens dma unmap for indirect
> 
> I think we need to explain why we need such hardening.


yes pls be more specific. Recording same state in two
places is just a source of bugs, not hardening.
Xuan Zhuo Sept. 12, 2024, 7:30 a.m. UTC | #3 
On Wed, 11 Sep 2024 11:46:30 +0800, Jason Wang <jasowang@redhat.com> wrote:
> On Tue, Aug 20, 2024 at 3:33 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
> >
> > 1. this commit hardens dma unmap for indirect
>
> I think we need to explain why we need such hardening. For example
> indirect use stream mapping which is read-only from the device. So it
> looks to me like it doesn't require hardening by itself.
>
> > 2. the subsequent commit uses the struct extra to record whether the
> >    buffers need to be unmapped or not.
>
> It's better to explain why such a decision could not be implied with
> the existing metadata.
>
> >  So we need a struct extra for
> >    every desc, whatever it is indirect or not.
>
> If this is the real reason, we need to tweak the title.

YES. It is.

I will tweak the title in next version.


>
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > ---
> >  drivers/virtio/virtio_ring.c | 122 ++++++++++++++++-------------------
> >  1 file changed, 57 insertions(+), 65 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > index 228e9fbcba3f..582d2c05498a 100644
> > --- a/drivers/virtio/virtio_ring.c
> > +++ b/drivers/virtio/virtio_ring.c
> > @@ -67,9 +67,16 @@
> >  #define LAST_ADD_TIME_INVALID(vq)
> >  #endif
> >
> > +struct vring_desc_extra {
> > +       dma_addr_t addr;                /* Descriptor DMA addr. */
> > +       u32 len;                        /* Descriptor length. */
> > +       u16 flags;                      /* Descriptor flags. */
> > +       u16 next;                       /* The next desc state in a list. */
> > +};
> > +
> >  struct vring_desc_state_split {
> >         void *data;                     /* Data for callback. */
> > -       struct vring_desc *indir_desc;  /* Indirect descriptor, if any. */
> > +       struct vring_desc_extra *indir; /* Indirect descriptor, if any. */
>
> Btw, it might be worth explaining that this will be allocated with an
> indirect descriptor table so we won't stress more to the memory
> allocator.

Will do.

Thanks.


>
> Thanks
>
>
diff mbox series

Patch

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 228e9fbcba3f..582d2c05498a 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -67,9 +67,16 @@ 
 #define LAST_ADD_TIME_INVALID(vq)
 #endif
 
+struct vring_desc_extra {
+	dma_addr_t addr;		/* Descriptor DMA addr. */
+	u32 len;			/* Descriptor length. */
+	u16 flags;			/* Descriptor flags. */
+	u16 next;			/* The next desc state in a list. */
+};
+
 struct vring_desc_state_split {
 	void *data;			/* Data for callback. */
-	struct vring_desc *indir_desc;	/* Indirect descriptor, if any. */
+	struct vring_desc_extra *indir;	/* Indirect descriptor, if any. */
 };
 
 struct vring_desc_state_packed {
@@ -79,13 +86,6 @@  struct vring_desc_state_packed {
 	u16 last;			/* The last desc state in a list. */
 };
 
-struct vring_desc_extra {
-	dma_addr_t addr;		/* Descriptor DMA addr. */
-	u32 len;			/* Descriptor length. */
-	u16 flags;			/* Descriptor flags. */
-	u16 next;			/* The next desc state in a list. */
-};
-
 struct vring_virtqueue_split {
 	/* Actual memory layout for this queue. */
 	struct vring vring;
@@ -440,38 +440,20 @@  static void virtqueue_init(struct vring_virtqueue *vq, u32 num)
  * Split ring specific functions - *_split().
  */
 
-static void vring_unmap_one_split_indirect(const struct vring_virtqueue *vq,
-					   const struct vring_desc *desc)
-{
-	u16 flags;
-
-	if (!vring_need_unmap_buffer(vq))
-		return;
-
-	flags = virtio16_to_cpu(vq->vq.vdev, desc->flags);
-
-	dma_unmap_page(vring_dma_dev(vq),
-		       virtio64_to_cpu(vq->vq.vdev, desc->addr),
-		       virtio32_to_cpu(vq->vq.vdev, desc->len),
-		       (flags & VRING_DESC_F_WRITE) ?
-		       DMA_FROM_DEVICE : DMA_TO_DEVICE);
-}
-
 static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq,
-					  unsigned int i)
+					  struct vring_desc_extra *extra)
 {
-	struct vring_desc_extra *extra = vq->split.desc_extra;
 	u16 flags;
 
-	flags = extra[i].flags;
+	flags = extra->flags;
 
 	if (flags & VRING_DESC_F_INDIRECT) {
 		if (!vq->use_dma_api)
 			goto out;
 
 		dma_unmap_single(vring_dma_dev(vq),
-				 extra[i].addr,
-				 extra[i].len,
+				 extra->addr,
+				 extra->len,
 				 (flags & VRING_DESC_F_WRITE) ?
 				 DMA_FROM_DEVICE : DMA_TO_DEVICE);
 	} else {
@@ -479,20 +461,22 @@  static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq,
 			goto out;
 
 		dma_unmap_page(vring_dma_dev(vq),
-			       extra[i].addr,
-			       extra[i].len,
+			       extra->addr,
+			       extra->len,
 			       (flags & VRING_DESC_F_WRITE) ?
 			       DMA_FROM_DEVICE : DMA_TO_DEVICE);
 	}
 
 out:
-	return extra[i].next;
+	return extra->next;
 }
 
 static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq,
 					       unsigned int total_sg,
+					       struct vring_desc_extra **pextra,
 					       gfp_t gfp)
 {
+	struct vring_desc_extra *extra;
 	struct vring_desc *desc;
 	unsigned int i;
 
@@ -503,40 +487,45 @@  static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq,
 	 */
 	gfp &= ~__GFP_HIGHMEM;
 
-	desc = kmalloc_array(total_sg, sizeof(struct vring_desc), gfp);
-	if (!desc)
+	extra = kmalloc_array(total_sg, sizeof(*desc) + sizeof(*extra), gfp);
+	if (!extra)
 		return NULL;
 
-	for (i = 0; i < total_sg; i++)
+	desc = (struct vring_desc *)&extra[total_sg];
+
+	for (i = 0; i < total_sg; i++) {
 		desc[i].next = cpu_to_virtio16(_vq->vdev, i + 1);
+		extra[i].next = i + 1;
+	}
+
+	*pextra = extra;
+
 	return desc;
 }
 
 static inline unsigned int virtqueue_add_desc_split(struct virtqueue *vq,
 						    struct vring_desc *desc,
+						    struct vring_desc_extra *extra,
 						    unsigned int i,
 						    dma_addr_t addr,
 						    unsigned int len,
 						    u16 flags,
 						    bool indirect)
 {
-	struct vring_virtqueue *vring = to_vvq(vq);
-	struct vring_desc_extra *extra = vring->split.desc_extra;
 	u16 next;
 
 	desc[i].flags = cpu_to_virtio16(vq->vdev, flags);
 	desc[i].addr = cpu_to_virtio64(vq->vdev, addr);
 	desc[i].len = cpu_to_virtio32(vq->vdev, len);
 
-	if (!indirect) {
-		next = extra[i].next;
-		desc[i].next = cpu_to_virtio16(vq->vdev, next);
+	extra[i].addr = addr;
+	extra[i].len = len;
+	extra[i].flags = flags;
 
-		extra[i].addr = addr;
-		extra[i].len = len;
-		extra[i].flags = flags;
-	} else
-		next = virtio16_to_cpu(vq->vdev, desc[i].next);
+	next = extra[i].next;
+
+	if (!indirect)
+		desc[i].next = cpu_to_virtio16(vq->vdev, next);
 
 	return next;
 }
@@ -551,6 +540,7 @@  static inline int virtqueue_add_split(struct virtqueue *_vq,
 				      gfp_t gfp)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
+	struct vring_desc_extra *extra;
 	struct scatterlist *sg;
 	struct vring_desc *desc;
 	unsigned int i, n, avail, descs_used, prev, err_idx;
@@ -574,7 +564,7 @@  static inline int virtqueue_add_split(struct virtqueue *_vq,
 	head = vq->free_head;
 
 	if (virtqueue_use_indirect(vq, total_sg))
-		desc = alloc_indirect_split(_vq, total_sg, gfp);
+		desc = alloc_indirect_split(_vq, total_sg, &extra, gfp);
 	else {
 		desc = NULL;
 		WARN_ON_ONCE(total_sg > vq->split.vring.num && !vq->indirect);
@@ -589,6 +579,7 @@  static inline int virtqueue_add_split(struct virtqueue *_vq,
 	} else {
 		indirect = false;
 		desc = vq->split.vring.desc;
+		extra = vq->split.desc_extra;
 		i = head;
 		descs_used = total_sg;
 	}
@@ -618,7 +609,7 @@  static inline int virtqueue_add_split(struct virtqueue *_vq,
 			/* Note that we trust indirect descriptor
 			 * table since it use stream DMA mapping.
 			 */
-			i = virtqueue_add_desc_split(_vq, desc, i, addr, sg->length,
+			i = virtqueue_add_desc_split(_vq, desc, extra, i, addr, sg->length,
 						     VRING_DESC_F_NEXT,
 						     indirect);
 		}
@@ -634,7 +625,7 @@  static inline int virtqueue_add_split(struct virtqueue *_vq,
 			/* Note that we trust indirect descriptor
 			 * table since it use stream DMA mapping.
 			 */
-			i = virtqueue_add_desc_split(_vq, desc, i, addr,
+			i = virtqueue_add_desc_split(_vq, desc, extra, i, addr,
 						     sg->length,
 						     VRING_DESC_F_NEXT |
 						     VRING_DESC_F_WRITE,
@@ -660,6 +651,7 @@  static inline int virtqueue_add_split(struct virtqueue *_vq,
 		}
 
 		virtqueue_add_desc_split(_vq, vq->split.vring.desc,
+					 vq->split.desc_extra,
 					 head, addr,
 					 total_sg * sizeof(struct vring_desc),
 					 VRING_DESC_F_INDIRECT,
@@ -678,9 +670,9 @@  static inline int virtqueue_add_split(struct virtqueue *_vq,
 	/* Store token and indirect buffer state. */
 	vq->split.desc_state[head].data = data;
 	if (indirect)
-		vq->split.desc_state[head].indir_desc = desc;
+		vq->split.desc_state[head].indir = extra;
 	else
-		vq->split.desc_state[head].indir_desc = ctx;
+		vq->split.desc_state[head].indir = ctx;
 
 	/* Put entry in available array (but don't update avail->idx until they
 	 * do sync). */
@@ -716,11 +708,8 @@  static inline int virtqueue_add_split(struct virtqueue *_vq,
 	for (n = 0; n < total_sg; n++) {
 		if (i == err_idx)
 			break;
-		if (indirect) {
-			vring_unmap_one_split_indirect(vq, &desc[i]);
-			i = virtio16_to_cpu(_vq->vdev, desc[i].next);
-		} else
-			i = vring_unmap_one_split(vq, i);
+
+		i = vring_unmap_one_split(vq, &extra[i]);
 	}
 
 free_indirect:
@@ -765,22 +754,25 @@  static bool virtqueue_kick_prepare_split(struct virtqueue *_vq)
 static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
 			     void **ctx)
 {
+	struct vring_desc_extra *extra;
 	unsigned int i, j;
 	__virtio16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
 
 	/* Clear data ptr. */
 	vq->split.desc_state[head].data = NULL;
 
+	extra = vq->split.desc_extra;
+
 	/* Put back on free list: unmap first-level descriptors and find end */
 	i = head;
 
 	while (vq->split.vring.desc[i].flags & nextflag) {
-		vring_unmap_one_split(vq, i);
+		vring_unmap_one_split(vq, &extra[i]);
 		i = vq->split.desc_extra[i].next;
 		vq->vq.num_free++;
 	}
 
-	vring_unmap_one_split(vq, i);
+	vring_unmap_one_split(vq, &extra[i]);
 	vq->split.desc_extra[i].next = vq->free_head;
 	vq->free_head = head;
 
@@ -788,12 +780,12 @@  static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
 	vq->vq.num_free++;
 
 	if (vq->indirect) {
-		struct vring_desc *indir_desc =
-				vq->split.desc_state[head].indir_desc;
 		u32 len;
 
+		extra = vq->split.desc_state[head].indir;
+
 		/* Free the indirect table, if any, now that it's unmapped. */
-		if (!indir_desc)
+		if (!extra)
 			return;
 
 		len = vq->split.desc_extra[head].len;
@@ -804,13 +796,13 @@  static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
 
 		if (vring_need_unmap_buffer(vq)) {
 			for (j = 0; j < len / sizeof(struct vring_desc); j++)
-				vring_unmap_one_split_indirect(vq, &indir_desc[j]);
+				vring_unmap_one_split(vq, &extra[j]);
 		}
 
-		kfree(indir_desc);
-		vq->split.desc_state[head].indir_desc = NULL;
+		kfree(extra);
+		vq->split.desc_state[head].indir = NULL;
 	} else if (ctx) {
-		*ctx = vq->split.desc_state[head].indir_desc;
+		*ctx = vq->split.desc_state[head].indir;
 	}
 }