Re: [PATCH net-next v2 3/5] virtio_ring: add packed ring support
From: Michael S. Tsirkin
Date: Wed Nov 07 2018 - 12:48:54 EST
On Wed, Jul 11, 2018 at 10:27:09AM +0800, Tiwei Bie wrote:
> This commit introduces the support (without EVENT_IDX) for
> packed ring.
>
> Signed-off-by: Tiwei Bie <tiwei.bie@xxxxxxxxx>
> ---
> drivers/virtio/virtio_ring.c | 495 ++++++++++++++++++++++++++++++++++-
> 1 file changed, 487 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index c4f8abc7445a..f317b485ba54 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -55,12 +55,21 @@
> #define END_USE(vq)
> #endif
>
> +#define _VRING_DESC_F_AVAIL(b) ((__u16)(b) << 7)
> +#define _VRING_DESC_F_USED(b) ((__u16)(b) << 15)
> +
> struct vring_desc_state {
> void *data; /* Data for callback. */
> struct vring_desc *indir_desc; /* Indirect descriptor, if any. */
> };
>
> struct vring_desc_state_packed {
> + void *data; /* Data for callback. */
> + struct vring_packed_desc *indir_desc; /* Indirect descriptor, if any. */
> + int num; /* Descriptor list length. */
> + dma_addr_t addr; /* Buffer DMA addr. */
> + u32 len; /* Buffer length. */
> + u16 flags; /* Descriptor flags. */
> int next; /* The next desc state. */
> };
>
> @@ -660,7 +669,6 @@ static bool virtqueue_poll_split(struct virtqueue *_vq, unsigned last_used_idx)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> - virtio_mb(vq->weak_barriers);
> return (u16)last_used_idx != virtio16_to_cpu(_vq->vdev, vq->vring.used->idx);
> }
>
> @@ -757,6 +765,72 @@ static inline unsigned vring_size_packed(unsigned int num, unsigned long align)
> & ~(align - 1)) + sizeof(struct vring_packed_desc_event) * 2;
> }
>
> +static void vring_unmap_state_packed(const struct vring_virtqueue *vq,
> + struct vring_desc_state_packed *state)
> +{
> + u16 flags;
> +
> + if (!vring_use_dma_api(vq->vq.vdev))
> + return;
> +
> + flags = state->flags;
> +
> + if (flags & VRING_DESC_F_INDIRECT) {
> + dma_unmap_single(vring_dma_dev(vq),
> + state->addr, state->len,
> + (flags & VRING_DESC_F_WRITE) ?
> + DMA_FROM_DEVICE : DMA_TO_DEVICE);
> + } else {
> + dma_unmap_page(vring_dma_dev(vq),
> + state->addr, state->len,
> + (flags & VRING_DESC_F_WRITE) ?
> + DMA_FROM_DEVICE : DMA_TO_DEVICE);
> + }
> +}
> +
> +static void vring_unmap_desc_packed(const struct vring_virtqueue *vq,
> + struct vring_packed_desc *desc)
> +{
> + u16 flags;
> +
> + if (!vring_use_dma_api(vq->vq.vdev))
> + return;
> +
> + flags = virtio16_to_cpu(vq->vq.vdev, desc->flags);
BTW this stuff is only used on error etc. Is there a way to
reuse vring_unmap_state_packed?
> +
> + if (flags & VRING_DESC_F_INDIRECT) {
> + dma_unmap_single(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);
> + } else {
> + 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 struct vring_packed_desc *alloc_indirect_packed(struct virtqueue *_vq,
> + unsigned int total_sg,
> + gfp_t gfp)
> +{
> + struct vring_packed_desc *desc;
> +
> + /*
> + * We require lowmem mappings for the descriptors because
> + * otherwise virt_to_phys will give us bogus addresses in the
> + * virtqueue.
> + */
> + gfp &= ~__GFP_HIGHMEM;
> +
> + desc = kmalloc(total_sg * sizeof(struct vring_packed_desc), gfp);
> +
> + return desc;
> +}
> +
> static inline int virtqueue_add_packed(struct virtqueue *_vq,
> struct scatterlist *sgs[],
> unsigned int total_sg,
> @@ -766,47 +840,449 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
> void *ctx,
> gfp_t gfp)
> {
> + struct vring_virtqueue *vq = to_vvq(_vq);
> + struct vring_packed_desc *desc;
> + struct scatterlist *sg;
> + unsigned int i, n, descs_used, uninitialized_var(prev), err_idx;
> + __virtio16 uninitialized_var(head_flags), flags;
> + u16 head, avail_wrap_counter, id, curr;
> + bool indirect;
> +
> + START_USE(vq);
> +
> + BUG_ON(data == NULL);
> + BUG_ON(ctx && vq->indirect);
> +
> + if (unlikely(vq->broken)) {
> + END_USE(vq);
> + return -EIO;
> + }
> +
> +#ifdef DEBUG
> + {
> + ktime_t now = ktime_get();
> +
> + /* No kick or get, with .1 second between? Warn. */
> + if (vq->last_add_time_valid)
> + WARN_ON(ktime_to_ms(ktime_sub(now, vq->last_add_time))
> + > 100);
> + vq->last_add_time = now;
> + vq->last_add_time_valid = true;
> + }
> +#endif
> +
> + BUG_ON(total_sg == 0);
> +
> + head = vq->next_avail_idx;
> + avail_wrap_counter = vq->avail_wrap_counter;
> +
> + if (virtqueue_use_indirect(_vq, total_sg))
> + desc = alloc_indirect_packed(_vq, total_sg, gfp);
> + else {
> + desc = NULL;
> + WARN_ON_ONCE(total_sg > vq->vring_packed.num && !vq->indirect);
> + }
> +
> + if (desc) {
> + /* Use a single buffer which doesn't continue */
> + indirect = true;
> + /* Set up rest to use this indirect table. */
> + i = 0;
> + descs_used = 1;
> + } else {
> + indirect = false;
> + desc = vq->vring_packed.desc;
> + i = head;
> + descs_used = total_sg;
> + }
> +
> + if (vq->vq.num_free < descs_used) {
> + pr_debug("Can't add buf len %i - avail = %i\n",
> + descs_used, vq->vq.num_free);
> + /* FIXME: for historical reasons, we force a notify here if
> + * there are outgoing parts to the buffer. Presumably the
> + * host should service the ring ASAP. */
I don't think we have a reason to do this for packed ring.
No historical baggage there, right?
> + if (out_sgs)
> + vq->notify(&vq->vq);
> + if (indirect)
> + kfree(desc);
> + END_USE(vq);
> + return -ENOSPC;
> + }
> +
> + id = vq->free_head;
> + BUG_ON(id == vq->vring_packed.num);
> +
> + curr = id;
> + for (n = 0; n < out_sgs + in_sgs; n++) {
> + for (sg = sgs[n]; sg; sg = sg_next(sg)) {
> + dma_addr_t addr = vring_map_one_sg(vq, sg, n < out_sgs ?
> + DMA_TO_DEVICE : DMA_FROM_DEVICE);
> + if (vring_mapping_error(vq, addr))
> + goto unmap_release;
> +
> + flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_NEXT |
> + (n < out_sgs ? 0 : VRING_DESC_F_WRITE) |
> + _VRING_DESC_F_AVAIL(vq->avail_wrap_counter) |
> + _VRING_DESC_F_USED(!vq->avail_wrap_counter));
> + if (!indirect && i == head)
> + head_flags = flags;
> + else
> + desc[i].flags = flags;
> +
> + desc[i].addr = cpu_to_virtio64(_vq->vdev, addr);
> + desc[i].len = cpu_to_virtio32(_vq->vdev, sg->length);
> + i++;
> + if (!indirect) {
> + if (vring_use_dma_api(_vq->vdev)) {
> + vq->desc_state_packed[curr].addr = addr;
> + vq->desc_state_packed[curr].len =
> + sg->length;
> + vq->desc_state_packed[curr].flags =
> + virtio16_to_cpu(_vq->vdev,
> + flags);
> + }
> + curr = vq->desc_state_packed[curr].next;
> +
> + if (i >= vq->vring_packed.num) {
> + i = 0;
> + vq->avail_wrap_counter ^= 1;
> + }
> + }
> + }
> + }
> +
> + prev = (i > 0 ? i : vq->vring_packed.num) - 1;
> + desc[prev].id = cpu_to_virtio16(_vq->vdev, id);
> +
> + /* Last one doesn't continue. */
> + if (total_sg == 1)
> + head_flags &= cpu_to_virtio16(_vq->vdev, ~VRING_DESC_F_NEXT);
> + else
> + desc[prev].flags &= cpu_to_virtio16(_vq->vdev,
> + ~VRING_DESC_F_NEXT);
> +
> + if (indirect) {
> + /* Now that the indirect table is filled in, map it. */
> + dma_addr_t addr = vring_map_single(
> + vq, desc, total_sg * sizeof(struct vring_packed_desc),
> + DMA_TO_DEVICE);
> + if (vring_mapping_error(vq, addr))
> + goto unmap_release;
> +
> + head_flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_INDIRECT |
> + _VRING_DESC_F_AVAIL(avail_wrap_counter) |
> + _VRING_DESC_F_USED(!avail_wrap_counter));
> + vq->vring_packed.desc[head].addr = cpu_to_virtio64(_vq->vdev,
> + addr);
> + vq->vring_packed.desc[head].len = cpu_to_virtio32(_vq->vdev,
> + total_sg * sizeof(struct vring_packed_desc));
> + vq->vring_packed.desc[head].id = cpu_to_virtio16(_vq->vdev, id);
> +
> + if (vring_use_dma_api(_vq->vdev)) {
> + vq->desc_state_packed[id].addr = addr;
> + vq->desc_state_packed[id].len = total_sg *
> + sizeof(struct vring_packed_desc);
> + vq->desc_state_packed[id].flags =
> + virtio16_to_cpu(_vq->vdev, head_flags);
> + }
> + }
> +
> + /* We're using some buffers from the free list. */
> + vq->vq.num_free -= descs_used;
> +
> + /* Update free pointer */
> + if (indirect) {
> + n = head + 1;
> + if (n >= vq->vring_packed.num) {
> + n = 0;
> + vq->avail_wrap_counter ^= 1;
> + }
> + vq->next_avail_idx = n;
> + vq->free_head = vq->desc_state_packed[id].next;
> + } else {
> + vq->next_avail_idx = i;
> + vq->free_head = curr;
> + }
> +
> + /* Store token and indirect buffer state. */
> + vq->desc_state_packed[id].num = descs_used;
> + vq->desc_state_packed[id].data = data;
> + if (indirect)
> + vq->desc_state_packed[id].indir_desc = desc;
> + else
> + vq->desc_state_packed[id].indir_desc = ctx;
> +
> + /* A driver MUST NOT make the first descriptor in the list
> + * available before all subsequent descriptors comprising
> + * the list are made available. */
> + virtio_wmb(vq->weak_barriers);
> + vq->vring_packed.desc[head].flags = head_flags;
> + vq->num_added += descs_used;
> +
> + pr_debug("Added buffer head %i to %p\n", head, vq);
> + END_USE(vq);
> +
> + return 0;
> +
> +unmap_release:
> + err_idx = i;
> + i = head;
> +
> + for (n = 0; n < total_sg; n++) {
> + if (i == err_idx)
> + break;
> + vring_unmap_desc_packed(vq, &desc[i]);
> + i++;
> + if (!indirect && i >= vq->vring_packed.num)
> + i = 0;
> + }
> +
> + vq->avail_wrap_counter = avail_wrap_counter;
> +
> + if (indirect)
> + kfree(desc);
> +
> + END_USE(vq);
> return -EIO;
> }
>
> static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq)
> {
> - return false;
> + struct vring_virtqueue *vq = to_vvq(_vq);
> + u16 flags;
> + bool needs_kick;
> + u32 snapshot;
> +
> + START_USE(vq);
> + /* We need to expose the new flags value before checking notification
> + * suppressions. */
> + virtio_mb(vq->weak_barriers);
> +
> + snapshot = READ_ONCE(*(u32 *)vq->vring_packed.device);
> + flags = virtio16_to_cpu(_vq->vdev, (__virtio16)(snapshot >> 16)) & 0x3;
> +
> +#ifdef DEBUG
> + if (vq->last_add_time_valid) {
> + WARN_ON(ktime_to_ms(ktime_sub(ktime_get(),
> + vq->last_add_time)) > 100);
> + }
> + vq->last_add_time_valid = false;
> +#endif
> +
> + needs_kick = (flags != VRING_EVENT_F_DISABLE);
> + END_USE(vq);
> + return needs_kick;
> +}
> +
> +static void detach_buf_packed(struct vring_virtqueue *vq,
> + unsigned int id, void **ctx)
> +{
> + struct vring_desc_state_packed *state = NULL;
> + struct vring_packed_desc *desc;
> + unsigned int curr, i;
> +
> + /* Clear data ptr. */
> + vq->desc_state_packed[id].data = NULL;
> +
> + curr = id;
> + for (i = 0; i < vq->desc_state_packed[id].num; i++) {
> + state = &vq->desc_state_packed[curr];
> + vring_unmap_state_packed(vq, state);
> + curr = state->next;
> + }
> +
> + BUG_ON(state == NULL);
> + vq->vq.num_free += vq->desc_state_packed[id].num;
> + state->next = vq->free_head;
> + vq->free_head = id;
> +
> + if (vq->indirect) {
> + u32 len;
> +
> + /* Free the indirect table, if any, now that it's unmapped. */
> + desc = vq->desc_state_packed[id].indir_desc;
> + if (!desc)
> + return;
> +
> + if (vring_use_dma_api(vq->vq.vdev)) {
> + len = vq->desc_state_packed[id].len;
> + for (i = 0; i < len / sizeof(struct vring_packed_desc);
> + i++)
> + vring_unmap_desc_packed(vq, &desc[i]);
> + }
> + kfree(desc);
> + vq->desc_state_packed[id].indir_desc = NULL;
> + } else if (ctx) {
> + *ctx = vq->desc_state_packed[id].indir_desc;
> + }
> +}
> +
> +static inline bool is_used_desc_packed(const struct vring_virtqueue *vq,
> + u16 idx, bool used_wrap_counter)
> +{
> + u16 flags;
> + bool avail, used;
> +
> + flags = virtio16_to_cpu(vq->vq.vdev,
> + vq->vring_packed.desc[idx].flags);
> + avail = !!(flags & VRING_DESC_F_AVAIL);
> + used = !!(flags & VRING_DESC_F_USED);
> +
> + return avail == used && used == used_wrap_counter;
> }
>
> static inline bool more_used_packed(const struct vring_virtqueue *vq)
> {
> - return false;
> + return is_used_desc_packed(vq, vq->last_used_idx,
> + vq->used_wrap_counter);
> }
>
> static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq,
> unsigned int *len,
> void **ctx)
> {
> - return NULL;
> + struct vring_virtqueue *vq = to_vvq(_vq);
> + u16 last_used, id;
> + void *ret;
> +
> + START_USE(vq);
> +
> + if (unlikely(vq->broken)) {
> + END_USE(vq);
> + return NULL;
> + }
> +
> + if (!more_used_packed(vq)) {
> + pr_debug("No more buffers in queue\n");
> + END_USE(vq);
> + return NULL;
> + }
> +
> + /* Only get used elements after they have been exposed by host. */
> + virtio_rmb(vq->weak_barriers);
> +
> + last_used = vq->last_used_idx;
> + id = virtio16_to_cpu(_vq->vdev, vq->vring_packed.desc[last_used].id);
> + *len = virtio32_to_cpu(_vq->vdev, vq->vring_packed.desc[last_used].len);
> +
> + if (unlikely(id >= vq->vring_packed.num)) {
> + BAD_RING(vq, "id %u out of range\n", id);
> + return NULL;
> + }
> + if (unlikely(!vq->desc_state_packed[id].data)) {
> + BAD_RING(vq, "id %u is not a head!\n", id);
> + return NULL;
> + }
> +
> + vq->last_used_idx += vq->desc_state_packed[id].num;
> + if (vq->last_used_idx >= vq->vring_packed.num) {
> + vq->last_used_idx -= vq->vring_packed.num;
> + vq->used_wrap_counter ^= 1;
> + }
> +
> + /* detach_buf_packed clears data, so grab it now. */
> + ret = vq->desc_state_packed[id].data;
> + detach_buf_packed(vq, id, ctx);
> +
> +#ifdef DEBUG
> + vq->last_add_time_valid = false;
> +#endif
> +
> + END_USE(vq);
> + return ret;
> }
>
> static void virtqueue_disable_cb_packed(struct virtqueue *_vq)
> {
> + struct vring_virtqueue *vq = to_vvq(_vq);
> +
> + if (vq->event_flags_shadow != VRING_EVENT_F_DISABLE) {
> + vq->event_flags_shadow = VRING_EVENT_F_DISABLE;
> + vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev,
> + vq->event_flags_shadow);
> + }
> }
>
> static unsigned virtqueue_enable_cb_prepare_packed(struct virtqueue *_vq)
> {
> - return 0;
> + struct vring_virtqueue *vq = to_vvq(_vq);
> +
> + START_USE(vq);
> +
> + /* We optimistically turn back on interrupts, then check if there was
> + * more to do. */
> +
> + if (vq->event_flags_shadow == VRING_EVENT_F_DISABLE) {
> + vq->event_flags_shadow = VRING_EVENT_F_ENABLE;
> + vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev,
> + vq->event_flags_shadow);
> + }
> +
> + END_USE(vq);
> + return vq->last_used_idx | ((u16)vq->used_wrap_counter << 15);
> }
>
> -static bool virtqueue_poll_packed(struct virtqueue *_vq, unsigned last_used_idx)
> +static bool virtqueue_poll_packed(struct virtqueue *_vq, unsigned off_wrap)
> {
> - return false;
> + struct vring_virtqueue *vq = to_vvq(_vq);
> + bool wrap_counter;
> + u16 used_idx;
> +
> + wrap_counter = off_wrap >> 15;
> + used_idx = off_wrap & ~(1 << 15);
> +
> + return is_used_desc_packed(vq, used_idx, wrap_counter);
> }
>
> static bool virtqueue_enable_cb_delayed_packed(struct virtqueue *_vq)
> {
> - return false;
> + struct vring_virtqueue *vq = to_vvq(_vq);
> +
> + START_USE(vq);
> +
> + /* We optimistically turn back on interrupts, then check if there was
> + * more to do. */
> +
> + if (vq->event_flags_shadow == VRING_EVENT_F_DISABLE) {
> + vq->event_flags_shadow = VRING_EVENT_F_ENABLE;
> + vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev,
> + vq->event_flags_shadow);
> + /* We need to enable interrupts first before re-checking
> + * for more used buffers. */
> + virtio_mb(vq->weak_barriers);
> + }
> +
> + if (more_used_packed(vq)) {
> + END_USE(vq);
> + return false;
> + }
> +
> + END_USE(vq);
> + return true;
> }
>
> static void *virtqueue_detach_unused_buf_packed(struct virtqueue *_vq)
> {
> + struct vring_virtqueue *vq = to_vvq(_vq);
> + unsigned int i;
> + void *buf;
> +
> + START_USE(vq);
> +
> + for (i = 0; i < vq->vring_packed.num; i++) {
> + if (!vq->desc_state_packed[i].data)
> + continue;
> + /* detach_buf clears data, so grab it now. */
> + buf = vq->desc_state_packed[i].data;
> + detach_buf_packed(vq, i, NULL);
> + END_USE(vq);
> + return buf;
> + }
> + /* That should have freed everything. */
> + BUG_ON(vq->vq.num_free != vq->vring_packed.num);
> +
> + END_USE(vq);
> return NULL;
> }
>
> @@ -1083,6 +1559,9 @@ bool virtqueue_poll(struct virtqueue *_vq, unsigned last_used_idx)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> + /* We need to enable interrupts first before re-checking
> + * for more used buffers. */
> + virtio_mb(vq->weak_barriers);
> return vq->packed ? virtqueue_poll_packed(_vq, last_used_idx) :
> virtqueue_poll_split(_vq, last_used_idx);
> }
> --
> 2.18.0