netdev - [PATCH vhost v7 05/11] virtio_ring: packed: support premapped

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Date:   Tue, 25 Apr 2023 15:36:07 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     virtualization@...ts.linux-foundation.org
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        Christoph Hellwig <hch@...radead.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexander Lobakin <aleksander.lobakin@...el.com>
Subject: [PATCH vhost v7 05/11] virtio_ring: packed: support premapped

virtio core only supports virtual addresses, dma is completed in virtio
core.

In some scenarios (such as the AF_XDP), the memory is allocated
and DMA mapping is completed in advance, so it is necessary for us to
support passing the DMA address to virtio core.

Drives can use sg->dma_address to pass the mapped dma address to virtio
core. If one sg->dma_address is used then all sgs must use
sg->dma_address, otherwise all must be null when passing it to the APIs
of virtio.

Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
---
 drivers/virtio/virtio_ring.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 055c1c069fff..4b6c6da4cdb4 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -81,6 +81,7 @@ struct vring_desc_state_packed {
 	struct vring_packed_desc *indir_desc; /* Indirect descriptor, if any. */
 	u16 num;			/* Descriptor list length. */
 	u16 last;			/* The last desc state in a list. */
+	u32 flags;			/* State flags. */
 };
 
 struct vring_desc_extra {
@@ -1272,7 +1273,8 @@ static u16 packed_last_used(u16 last_used_idx)
 }
 
 static void vring_unmap_extra_packed(const struct vring_virtqueue *vq,
-				     const struct vring_desc_extra *extra)
+				     const struct vring_desc_extra *extra,
+				     bool dma_map_internal)
 {
 	u16 flags;
 
@@ -1287,6 +1289,9 @@ static void vring_unmap_extra_packed(const struct vring_virtqueue *vq,
 				 (flags & VRING_DESC_F_WRITE) ?
 				 DMA_FROM_DEVICE : DMA_TO_DEVICE);
 	} else {
+		if (!dma_map_internal)
+			return;
+
 		dma_unmap_page(vring_dma_dev(vq),
 			       extra->addr, extra->len,
 			       (flags & VRING_DESC_F_WRITE) ?
@@ -1453,6 +1458,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
 	unsigned int i, n, c, descs_used;
 	__le16 head_flags, flags;
 	u16 head, id, prev, curr;
+	bool dma_map_internal;
 	int err;
 
 	START_USE(vq);
@@ -1498,7 +1504,8 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
 	id = vq->free_head;
 	BUG_ON(id == vq->packed.vring.num);
 
-	if (virtqueue_map_sgs(vq, sgs, total_sg, out_sgs, in_sgs)) {
+	dma_map_internal = !sgs[0]->dma_address;
+	if (dma_map_internal && virtqueue_map_sgs(vq, sgs, total_sg, out_sgs, in_sgs)) {
 		END_USE(vq);
 		return -EIO;
 	}
@@ -1552,6 +1559,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
 	vq->packed.desc_state[id].data = data;
 	vq->packed.desc_state[id].indir_desc = ctx;
 	vq->packed.desc_state[id].last = prev;
+	vq->packed.desc_state[id].flags = dma_map_internal ? VRING_STATE_F_MAP_INTERNAL : 0;
 
 	/*
 	 * A driver MUST NOT make the first descriptor in the list
@@ -1623,8 +1631,10 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
 	struct vring_desc_state_packed *state = NULL;
 	struct vring_packed_desc *desc;
 	unsigned int i, curr;
+	bool dma_map_internal;
 
 	state = &vq->packed.desc_state[id];
+	dma_map_internal = !!(state->flags & VRING_STATE_F_MAP_INTERNAL);
 
 	/* Clear data ptr. */
 	state->data = NULL;
@@ -1637,7 +1647,8 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
 		curr = id;
 		for (i = 0; i < state->num; i++) {
 			vring_unmap_extra_packed(vq,
-						 &vq->packed.desc_extra[curr]);
+						 &vq->packed.desc_extra[curr],
+						 dma_map_internal);
 			curr = vq->packed.desc_extra[curr].next;
 		}
 	}
-- 
2.32.0.3.g01195cf9f