The shared descriptors should only be written by the guest driver, however, the device is still able to overwrite and corrupt them. Maintain a private shadow copy of the descriptors for the driver to use for state tracking, removing the need to read from the shared descriptors.
Signed-off-by: Andrew Scull ascull@google.com Reviewed-by: Simon Glass sjg@chromium.org --- drivers/virtio/virtio_ring.c | 49 ++++++++++++++++++++++++------------ include/virtio_ring.h | 10 ++++++++ 2 files changed, 43 insertions(+), 16 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index d3fc842f30..73671d79da 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -19,13 +19,21 @@ static unsigned int virtqueue_attach_desc(struct virtqueue *vq, unsigned int i, struct virtio_sg *sg, u16 flags) { + struct vring_desc_shadow *desc_shadow = &vq->vring_desc_shadow[i]; struct vring_desc *desc = &vq->vring.desc[i];
- desc->addr = cpu_to_virtio64(vq->vdev, (u64)(uintptr_t)sg->addr); - desc->len = cpu_to_virtio32(vq->vdev, sg->length); - desc->flags = cpu_to_virtio16(vq->vdev, flags); + /* Update the shadow descriptor. */ + desc_shadow->addr = (u64)(uintptr_t)sg->addr; + desc_shadow->len = sg->length; + desc_shadow->flags = flags;
- return virtio16_to_cpu(vq->vdev, desc->next); + /* Update the shared descriptor to match the shadow. */ + desc->addr = cpu_to_virtio64(vq->vdev, desc_shadow->addr); + desc->len = cpu_to_virtio32(vq->vdev, desc_shadow->len); + desc->flags = cpu_to_virtio16(vq->vdev, desc_shadow->flags); + desc->next = cpu_to_virtio16(vq->vdev, desc_shadow->next); + + return desc_shadow->next; }
int virtqueue_add(struct virtqueue *vq, struct virtio_sg *sgs[], @@ -65,7 +73,8 @@ int virtqueue_add(struct virtqueue *vq, struct virtio_sg *sgs[], i = virtqueue_attach_desc(vq, i, sgs[n], flags); } /* Last one doesn't continue */ - desc[prev].flags &= cpu_to_virtio16(vq->vdev, ~VRING_DESC_F_NEXT); + vq->vring_desc_shadow[prev].flags &= ~VRING_DESC_F_NEXT; + desc[prev].flags = cpu_to_virtio16(vq->vdev, vq->vring_desc_shadow[prev].flags);
/* We're using some buffers from the free list. */ vq->num_free -= descs_used; @@ -134,17 +143,16 @@ void virtqueue_kick(struct virtqueue *vq) static void detach_buf(struct virtqueue *vq, unsigned int head) { unsigned int i; - __virtio16 nextflag = cpu_to_virtio16(vq->vdev, VRING_DESC_F_NEXT);
/* Put back on free list: unmap first-level descriptors and find end */ i = head;
- while (vq->vring.desc[i].flags & nextflag) { - i = virtio16_to_cpu(vq->vdev, vq->vring.desc[i].next); + while (vq->vring_desc_shadow[i].flags & VRING_DESC_F_NEXT) { + i = vq->vring_desc_shadow[i].next; vq->num_free++; }
- vq->vring.desc[i].next = cpu_to_virtio16(vq->vdev, vq->free_head); + vq->vring_desc_shadow[i].next = vq->free_head; vq->free_head = head;
/* Plus final descriptor */ @@ -197,8 +205,7 @@ void *virtqueue_get_buf(struct virtqueue *vq, unsigned int *len) virtio_store_mb(&vring_used_event(&vq->vring), cpu_to_virtio16(vq->vdev, vq->last_used_idx));
- return (void *)(uintptr_t)virtio64_to_cpu(vq->vdev, - vq->vring.desc[i].addr); + return (void *)(uintptr_t)vq->vring_desc_shadow[i].addr; }
static struct virtqueue *__vring_new_virtqueue(unsigned int index, @@ -207,6 +214,7 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index, { unsigned int i; struct virtqueue *vq; + struct vring_desc_shadow *vring_desc_shadow; struct virtio_dev_priv *uc_priv = dev_get_uclass_priv(udev); struct udevice *vdev = uc_priv->vdev;
@@ -214,10 +222,17 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index, if (!vq) return NULL;
+ vring_desc_shadow = calloc(vring.num, sizeof(struct vring_desc_shadow)); + if (!vring_desc_shadow) { + free(vq); + return NULL; + } + vq->vdev = vdev; vq->index = index; vq->num_free = vring.num; vq->vring = vring; + vq->vring_desc_shadow = vring_desc_shadow; vq->last_used_idx = 0; vq->avail_flags_shadow = 0; vq->avail_idx_shadow = 0; @@ -235,7 +250,7 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index, /* Put everything in free lists */ vq->free_head = 0; for (i = 0; i < vring.num - 1; i++) - vq->vring.desc[i].next = cpu_to_virtio16(vdev, i + 1); + vq->vring_desc_shadow[i].next = i + 1;
return vq; } @@ -288,6 +303,7 @@ struct virtqueue *vring_create_virtqueue(unsigned int index, unsigned int num, void vring_del_virtqueue(struct virtqueue *vq) { free(vq->vring.desc); + free(vq->vring_desc_shadow); list_del(&vq->list); free(vq); } @@ -333,11 +349,12 @@ void virtqueue_dump(struct virtqueue *vq) printf("\tlast_used_idx %u, avail_flags_shadow %u, avail_idx_shadow %u\n", vq->last_used_idx, vq->avail_flags_shadow, vq->avail_idx_shadow);
- printf("Descriptor dump:\n"); + printf("Shadow descriptor dump:\n"); for (i = 0; i < vq->vring.num; i++) { - printf("\tdesc[%u] = { 0x%llx, len %u, flags %u, next %u }\n", - i, vq->vring.desc[i].addr, vq->vring.desc[i].len, - vq->vring.desc[i].flags, vq->vring.desc[i].next); + struct vring_desc_shadow *desc = &vq->vring_desc_shadow[i]; + + printf("\tdesc_shadow[%u] = { 0x%llx, len %u, flags %u, next %u }\n", + i, desc->addr, desc->len, desc->flags, desc->next); }
printf("Avail ring dump:\n"); diff --git a/include/virtio_ring.h b/include/virtio_ring.h index 6fc0593b14..52cbe77c0a 100644 --- a/include/virtio_ring.h +++ b/include/virtio_ring.h @@ -55,6 +55,14 @@ struct vring_desc { __virtio16 next; };
+/* Shadow of struct vring_desc in guest byte order. */ +struct vring_desc_shadow { + u64 addr; + u32 len; + u16 flags; + u16 next; +}; + struct vring_avail { __virtio16 flags; __virtio16 idx; @@ -89,6 +97,7 @@ struct vring { * @index: the zero-based ordinal number for this queue * @num_free: number of elements we expect to be able to fit * @vring: actual memory layout for this queue + * @vring_desc_shadow: guest-only copy of descriptors * @event: host publishes avail event idx * @free_head: head of free buffer list * @num_added: number we've added since last sync @@ -102,6 +111,7 @@ struct virtqueue { unsigned int index; unsigned int num_free; struct vring vring; + struct vring_desc_shadow *vring_desc_shadow; bool event; unsigned int free_head; unsigned int num_added;