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Message-Id: <20240716064628.1950-4-xuanzhuo@linux.alibaba.com>
Date: Tue, 16 Jul 2024 14:46:18 +0800
From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To: netdev@...r.kernel.org
Cc: "Michael S. Tsirkin" <mst@...hat.com>,
	Jason Wang <jasowang@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Eugenio PĂ©rez <eperezma@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	virtualization@...ts.linux.dev,
	bpf@...r.kernel.org
Subject: [RFC net-next 03/13] virtio_ring: packed: harden dma unmap for indirect

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@...ux.alibaba.com>
---
 drivers/virtio/virtio_ring.c | 57 ++++++++++++++++++------------------
 1 file changed, 29 insertions(+), 28 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 1e037da542b9..5fb94f735edb 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -81,7 +81,7 @@ struct vring_desc_state_split {
 
 struct vring_desc_state_packed {
 	void *data;			/* Data for callback. */
-	struct vring_packed_desc *indir_desc; /* Indirect descriptor, if any. */
+	struct vring_desc_extra *indir; /* Indirect descriptor, if any. */
 	u16 num;			/* Descriptor list length. */
 	u16 last;			/* The last desc state in a list. */
 };
@@ -1238,27 +1238,13 @@ static void vring_unmap_extra_packed(const struct vring_virtqueue *vq,
 	}
 }
 
-static void vring_unmap_desc_packed(const struct vring_virtqueue *vq,
-				    const struct vring_packed_desc *desc)
-{
-	u16 flags;
-
-	if (!vring_need_unmap_buffer(vq))
-		return;
-
-	flags = le16_to_cpu(desc->flags);
-
-	dma_unmap_page(vring_dma_dev(vq),
-		       le64_to_cpu(desc->addr),
-		       le32_to_cpu(desc->len),
-		       (flags & VRING_DESC_F_WRITE) ?
-		       DMA_FROM_DEVICE : DMA_TO_DEVICE);
-}
-
 static struct vring_packed_desc *alloc_indirect_packed(unsigned int total_sg,
+						       struct vring_desc_extra **pextra,
 						       gfp_t gfp)
 {
+	struct vring_desc_extra *extra;
 	struct vring_packed_desc *desc;
+	int i;
 
 	/*
 	 * We require lowmem mappings for the descriptors because
@@ -1267,7 +1253,14 @@ static struct vring_packed_desc *alloc_indirect_packed(unsigned int total_sg,
 	 */
 	gfp &= ~__GFP_HIGHMEM;
 
-	desc = kmalloc_array(total_sg, sizeof(struct vring_packed_desc), gfp);
+	extra = kmalloc_array(total_sg, sizeof(*desc) + sizeof(*extra), gfp);
+
+	desc = (struct vring_packed_desc *)&extra[total_sg];
+
+	for (i = 0; i < total_sg; i++)
+		extra[i].next = i + 1;
+
+	*pextra = extra;
 
 	return desc;
 }
@@ -1280,6 +1273,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
 					 void *data,
 					 gfp_t gfp)
 {
+	struct vring_desc_extra *extra;
 	struct vring_packed_desc *desc;
 	struct scatterlist *sg;
 	unsigned int i, n, err_idx;
@@ -1287,7 +1281,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
 	dma_addr_t addr;
 
 	head = vq->packed.next_avail_idx;
-	desc = alloc_indirect_packed(total_sg, gfp);
+	desc = alloc_indirect_packed(total_sg, &extra, gfp);
 	if (!desc)
 		return -ENOMEM;
 
@@ -1313,6 +1307,12 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
 			desc[i].addr = cpu_to_le64(addr);
 			desc[i].len = cpu_to_le32(sg->length);
 			i++;
+
+			if (unlikely(vq->use_dma_api)) {
+				extra[i].addr = addr;
+				extra[i].len = sg->length;
+				extra[i].flags = n < out_sgs ?  0 : VRING_DESC_F_WRITE;
+			}
 		}
 	}
 
@@ -1367,7 +1367,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
 	/* Store token and indirect buffer state. */
 	vq->packed.desc_state[id].num = 1;
 	vq->packed.desc_state[id].data = data;
-	vq->packed.desc_state[id].indir_desc = desc;
+	vq->packed.desc_state[id].indir = extra;
 	vq->packed.desc_state[id].last = id;
 
 	vq->num_added += 1;
@@ -1381,7 +1381,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
 	err_idx = i;
 
 	for (i = 0; i < err_idx; i++)
-		vring_unmap_desc_packed(vq, &desc[i]);
+		vring_unmap_extra_packed(vq, &extra[i]);
 
 free_desc:
 	kfree(desc);
@@ -1504,7 +1504,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
 	/* Store token. */
 	vq->packed.desc_state[id].num = descs_used;
 	vq->packed.desc_state[id].data = data;
-	vq->packed.desc_state[id].indir_desc = ctx;
+	vq->packed.desc_state[id].indir = ctx;
 	vq->packed.desc_state[id].last = prev;
 
 	/*
@@ -1617,23 +1617,24 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
 	}
 
 	if (vq->indirect) {
+		struct vring_desc_extra *extra;
 		u32 len;
 
 		/* Free the indirect table, if any, now that it's unmapped. */
-		desc = state->indir_desc;
-		if (!desc)
+		extra = state->indir;
+		if (!extra)
 			return;
 
 		if (vring_need_unmap_buffer(vq)) {
 			len = vq->packed.desc_extra[id].len;
 			for (i = 0; i < len / sizeof(struct vring_packed_desc);
 					i++)
-				vring_unmap_desc_packed(vq, &desc[i]);
+				vring_unmap_extra_packed(vq, &extra[i]);
 		}
 		kfree(desc);
-		state->indir_desc = NULL;
+		state->indir = NULL;
 	} else if (ctx) {
-		*ctx = state->indir_desc;
+		*ctx = state->indir;
 	}
 }
 
-- 
2.32.0.3.g01195cf9f


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