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SubjectRe: [PATCH RFC 2/2] virtio_ring: support packed ring
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On 2018年02月23日 19:18, Tiwei Bie wrote:
> Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
> ---
> drivers/virtio/virtio_ring.c | 699 +++++++++++++++++++++++++++++++++++++------
> include/linux/virtio_ring.h | 8 +-
> 2 files changed, 618 insertions(+), 89 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index eb30f3e09a47..393778a2f809 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -58,14 +58,14 @@
>
> struct vring_desc_state {
> void *data; /* Data for callback. */
> - struct vring_desc *indir_desc; /* Indirect descriptor, if any. */
> + void *indir_desc; /* Indirect descriptor, if any. */
> + int num; /* Descriptor list length. */
> };
>
> struct vring_virtqueue {
> struct virtqueue vq;
>
> - /* Actual memory layout for this queue */
> - struct vring vring;
> + bool packed;
>
> /* Can we use weak barriers? */
> bool weak_barriers;
> @@ -87,11 +87,28 @@ struct vring_virtqueue {
> /* Last used index we've seen. */
> u16 last_used_idx;
>
> - /* Last written value to avail->flags */
> - u16 avail_flags_shadow;
> -
> - /* Last written value to avail->idx in guest byte order */
> - u16 avail_idx_shadow;
> + union {
> + /* Available for split ring */
> + struct {
> + /* Actual memory layout for this queue */
> + struct vring vring;
> +
> + /* Last written value to avail->flags */
> + u16 avail_flags_shadow;
> +
> + /* Last written value to avail->idx in
> + * guest byte order */
> + u16 avail_idx_shadow;
> + };
> +
> + /* Available for packed ring */
> + struct {
> + /* Actual memory layout for this queue */
> + struct vring_packed vring_packed;
> + u8 wrap_counter : 1;
> + bool chaining;
> + };
> + };
>
> /* How to notify other side. FIXME: commonalize hcalls! */
> bool (*notify)(struct virtqueue *vq);
> @@ -201,26 +218,37 @@ static dma_addr_t vring_map_single(const struct vring_virtqueue *vq,
> cpu_addr, size, direction);
> }
>
> -static void vring_unmap_one(const struct vring_virtqueue *vq,
> - struct vring_desc *desc)
> +static void vring_unmap_one(const struct vring_virtqueue *vq, void *_desc)
> {

Let's split the helpers to packed/split version like other helpers?
(Consider the caller has already known the type of vq).

> + u64 addr;
> + u32 len;
> u16 flags;
>
> if (!vring_use_dma_api(vq->vq.vdev))
> return;
>
> - flags = virtio16_to_cpu(vq->vq.vdev, desc->flags);
> + if (vq->packed) {
> + struct vring_packed_desc *desc = _desc;
> +
> + addr = virtio64_to_cpu(vq->vq.vdev, desc->addr);
> + len = virtio32_to_cpu(vq->vq.vdev, desc->len);
> + flags = virtio16_to_cpu(vq->vq.vdev, desc->flags);
> + } else {
> + struct vring_desc *desc = _desc;
> +
> + addr = virtio64_to_cpu(vq->vq.vdev, desc->addr);
> + len = virtio32_to_cpu(vq->vq.vdev, desc->len);
> + flags = virtio16_to_cpu(vq->vq.vdev, desc->flags);
> + }
>
> 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),
> + addr, 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),
> + addr, len,
> (flags & VRING_DESC_F_WRITE) ?
> DMA_FROM_DEVICE : DMA_TO_DEVICE);
> }
> @@ -235,8 +263,9 @@ static int vring_mapping_error(const struct vring_virtqueue *vq,
> return dma_mapping_error(vring_dma_dev(vq), addr);
> }
>
> -static struct vring_desc *alloc_indirect(struct virtqueue *_vq,
> - unsigned int total_sg, gfp_t gfp)
> +static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq,
> + unsigned int total_sg,
> + gfp_t gfp)
> {
> struct vring_desc *desc;
> unsigned int i;
> @@ -257,14 +286,32 @@ static struct vring_desc *alloc_indirect(struct virtqueue *_vq,
> return desc;
> }
>
> -static inline int virtqueue_add(struct virtqueue *_vq,
> - struct scatterlist *sgs[],
> - unsigned int total_sg,
> - unsigned int out_sgs,
> - unsigned int in_sgs,
> - void *data,
> - void *ctx,
> - gfp_t gfp)
> +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_split(struct virtqueue *_vq,
> + struct scatterlist *sgs[],
> + unsigned int total_sg,
> + unsigned int out_sgs,
> + unsigned int in_sgs,
> + void *data,
> + void *ctx,
> + gfp_t gfp)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
> struct scatterlist *sg;
> @@ -303,7 +350,7 @@ static inline int virtqueue_add(struct virtqueue *_vq,
> /* If the host supports indirect descriptor tables, and we have multiple
> * buffers, then go indirect. FIXME: tune this threshold */
> if (vq->indirect && total_sg > 1 && vq->vq.num_free)
> - desc = alloc_indirect(_vq, total_sg, gfp);
> + desc = alloc_indirect_split(_vq, total_sg, gfp);
> else {
> desc = NULL;
> WARN_ON_ONCE(total_sg > vq->vring.num && !vq->indirect);
> @@ -437,6 +484,243 @@ static inline int virtqueue_add(struct virtqueue *_vq,
> return -EIO;
> }
>
> +static inline int virtqueue_add_packed(struct virtqueue *_vq,
> + struct scatterlist *sgs[],
> + unsigned int total_sg,
> + unsigned int out_sgs,
> + unsigned int in_sgs,
> + void *data,
> + 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;
> + int head, wrap_counter;
> + bool indirect;
> +
> + START_USE(vq);
> +
> + BUG_ON(data == NULL);
> + BUG_ON(ctx && vq->indirect);
> +
> + if (unlikely(vq->broken)) {
> + END_USE(vq);
> + return -EIO;
> + }
> +
> + if (total_sg > 1 && !vq->chaining && !vq->indirect) {
> + END_USE(vq);
> + return -ENOTSUPP;
> + }
> +
> +#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->free_head;
> + wrap_counter = vq->wrap_counter;
> +
> + /* If the host supports indirect descriptor tables, and we have multiple
> + * buffers, then go indirect. FIXME: tune this threshold */
> + if (vq->indirect && total_sg > 1 && vq->vq.num_free)
> + desc = alloc_indirect_packed(_vq, total_sg, gfp);
> + else {
> + desc = NULL;
> + WARN_ON_ONCE(total_sg > vq->vring.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 (total_sg > 1 && !vq->chaining) {
> + END_USE(vq);
> + return -ENOTSUPP;
> + }
> + }
> +
> + 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. */
> + if (out_sgs)
> + vq->notify(&vq->vq);
> + if (indirect)
> + kfree(desc);
> + END_USE(vq);
> + return -ENOSPC;
> + }
> +
> + for (n = 0; n < out_sgs; n++) {
> + for (sg = sgs[n]; sg; sg = sg_next(sg)) {
> + dma_addr_t addr = vring_map_one_sg(vq, sg, DMA_TO_DEVICE);
> + if (vring_mapping_error(vq, addr))
> + goto unmap_release;
> +
> + flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_NEXT |
> + VRING_DESC_F_AVAIL(vq->wrap_counter) |
> + VRING_DESC_F_USED(!vq->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);
> + desc[i].id = cpu_to_virtio32(_vq->vdev, head);

If it's a part of chain, we only need to do this for last buffer I think.

> + prev = i;
> + i++;

It looks to me prev is always i - 1?

> + if (!indirect && i >= vq->vring_packed.num) {
> + i = 0;
> + vq->wrap_counter ^= 1;
> + }
> + }
> + }
> + for (; 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, DMA_FROM_DEVICE);
> + if (vring_mapping_error(vq, addr))
> + goto unmap_release;
> +
> + flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_NEXT |
> + VRING_DESC_F_WRITE |
> + VRING_DESC_F_AVAIL(vq->wrap_counter) |
> + VRING_DESC_F_USED(!vq->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);
> + desc[i].id = cpu_to_virtio32(_vq->vdev, head);
> + prev = i;
> + i++;
> + if (!indirect && i >= vq->vring_packed.num) {
> + i = 0;
> + vq->wrap_counter ^= 1;
> + }
> + }
> + }
> + /* Last one doesn't continue. */
> + if (!indirect && (head + 1) % vq->vring_packed.num == i)
> + head_flags &= cpu_to_virtio16(_vq->vdev, ~VRING_DESC_F_NEXT);

I can't get the why we need this here.

> + else
> + desc[prev].flags &= cpu_to_virtio16(_vq->vdev, ~VRING_DESC_F_NEXT);
> +
> + if (indirect) {
> + /* FIXME: to be implemented */
> +
> + /* 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(wrap_counter) |
> + VRING_DESC_F_USED(!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_virtio32(_vq->vdev, head);
> + }
> +
> + /* 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->wrap_counter ^= 1;
> + }
> + vq->free_head = n;

detach_buf_packed() does not even touch free_head here, so need to
explain its meaning for packed ring.

> + } else
> + vq->free_head = i;

ID is only valid in the last descriptor in the list, so head + 1 should
be ok too?

> +
> + /* Store token and indirect buffer state. */
> + vq->desc_state[head].num = descs_used;
> + vq->desc_state[head].data = data;
> + if (indirect)
> + vq->desc_state[head].indir_desc = desc;
> + else
> + vq->desc_state[head].indir_desc = ctx;
> +
> + virtio_wmb(vq->weak_barriers);

Let's add a comment to explain the barrier here.

> + vq->vring_packed.desc[head].flags = head_flags;
> + vq->num_added++;
> +
> + 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_one(vq, &desc[i]);
> + i++;
> + if (!indirect && i >= vq->vring_packed.num)
> + i = 0;
> + }
> +
> + vq->wrap_counter = wrap_counter;
> +
> + if (indirect)
> + kfree(desc);
> +
> + END_USE(vq);
> + return -EIO;
> +}
> +
> +static inline int virtqueue_add(struct virtqueue *_vq,
> + struct scatterlist *sgs[],
> + unsigned int total_sg,
> + unsigned int out_sgs,
> + unsigned int in_sgs,
> + void *data,
> + void *ctx,
> + gfp_t gfp)
> +{
> + struct vring_virtqueue *vq = to_vvq(_vq);
> +
> + return vq->packed ? virtqueue_add_packed(_vq, sgs, total_sg, out_sgs,
> + in_sgs, data, ctx, gfp) :
> + virtqueue_add_split(_vq, sgs, total_sg, out_sgs,
> + in_sgs, data, ctx, gfp);
> +}
> +
> /**
> * virtqueue_add_sgs - expose buffers to other end
> * @vq: the struct virtqueue we're talking about.
> @@ -561,6 +845,12 @@ bool virtqueue_kick_prepare(struct virtqueue *_vq)
> * event. */
> virtio_mb(vq->weak_barriers);
>
> + if (vq->packed) {
> + /* FIXME: to be implemented */
> + needs_kick = true;
> + goto out;
> + }
> +
> old = vq->avail_idx_shadow - vq->num_added;
> new = vq->avail_idx_shadow;
> vq->num_added = 0;
> @@ -579,6 +869,8 @@ bool virtqueue_kick_prepare(struct virtqueue *_vq)
> } else {
> needs_kick = !(vq->vring.used->flags & cpu_to_virtio16(_vq->vdev, VRING_USED_F_NO_NOTIFY));
> }
> +
> +out:
> END_USE(vq);
> return needs_kick;
> }
> @@ -628,8 +920,8 @@ bool virtqueue_kick(struct virtqueue *vq)
> }
> EXPORT_SYMBOL_GPL(virtqueue_kick);
>
> -static void detach_buf(struct vring_virtqueue *vq, unsigned int head,
> - void **ctx)
> +static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
> + void **ctx)
> {
> unsigned int i, j;
> __virtio16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
> @@ -677,29 +969,81 @@ static void detach_buf(struct vring_virtqueue *vq, unsigned int head,
> }
> }
>
> -static inline bool more_used(const struct vring_virtqueue *vq)
> +static void detach_buf_packed(struct vring_virtqueue *vq, unsigned int head,
> + void **ctx)
> +{
> + struct vring_packed_desc *desc;
> + unsigned int i, j;
> +
> + /* Clear data ptr. */
> + vq->desc_state[head].data = NULL;
> +
> + i = head;
> +
> + for (j = 0; j < vq->desc_state[head].num; j++) {
> + desc = &vq->vring_packed.desc[i];
> + vring_unmap_one(vq, desc);
> + i++;
> + if (i >= vq->vring_packed.num)
> + i = 0;
> + }
> +
> + vq->vq.num_free += vq->desc_state[head].num;

It looks to me vq->free_head grows always, how can we make sure it does
not exceeds vq.num here?

> +
> + if (vq->indirect) {
> + u32 len;
> +
> + desc = vq->desc_state[head].indir_desc;
> + /* Free the indirect table, if any, now that it's unmapped. */
> + if (!desc)
> + return;
> +
> + len = virtio32_to_cpu(vq->vq.vdev,
> + vq->vring_packed.desc[head].len);
> +
> + BUG_ON(!(vq->vring_packed.desc[head].flags &
> + cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_INDIRECT)));
> + BUG_ON(len == 0 || len % sizeof(struct vring_packed_desc));
> +
> + for (j = 0; j < len / sizeof(struct vring_packed_desc); j++)
> + vring_unmap_one(vq, &desc[j]);
> +
> + kfree(desc);
> + vq->desc_state[head].indir_desc = NULL;
> + } else if (ctx) {
> + *ctx = vq->desc_state[head].indir_desc;
> + }
> +}
> +
> +static inline bool more_used_split(const struct vring_virtqueue *vq)
> {
> return vq->last_used_idx != virtio16_to_cpu(vq->vq.vdev, vq->vring.used->idx);
> }
>
> -/**
> - * virtqueue_get_buf - get the next used buffer
> - * @vq: the struct virtqueue we're talking about.
> - * @len: the length written into the buffer
> - *
> - * If the device wrote data into the buffer, @len will be set to the
> - * amount written. This means you don't need to clear the buffer
> - * beforehand to ensure there's no data leakage in the case of short
> - * writes.
> - *
> - * Caller must ensure we don't call this with other virtqueue
> - * operations at the same time (except where noted).
> - *
> - * Returns NULL if there are no used buffers, or the "data" token
> - * handed to virtqueue_add_*().
> - */
> -void *virtqueue_get_buf_ctx(struct virtqueue *_vq, unsigned int *len,
> - void **ctx)
> +static inline bool more_used_packed(const struct vring_virtqueue *vq)
> +{
> + u16 last_used, flags;
> + bool avail, used;
> +
> + if (vq->vq.num_free == vq->vring.num)
> + return false;
> +
> + last_used = vq->last_used_idx;
> + flags = virtio16_to_cpu(vq->vq.vdev,
> + vq->vring_packed.desc[last_used].flags);
> + avail = flags & VRING_DESC_F_AVAIL(1);
> + used = flags & VRING_DESC_F_USED(1);
> +
> + return avail == used;
> +}
> +
> +static inline bool more_used(const struct vring_virtqueue *vq)
> +{
> + return vq->packed ? more_used_packed(vq) : more_used_split(vq);
> +}
> +
> +void *virtqueue_get_buf_ctx_split(struct virtqueue *_vq, unsigned int *len,
> + void **ctx)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
> void *ret;
> @@ -735,9 +1079,9 @@ void *virtqueue_get_buf_ctx(struct virtqueue *_vq, unsigned int *len,
> return NULL;
> }
>
> - /* detach_buf clears data, so grab it now. */
> + /* detach_buf_split clears data, so grab it now. */
> ret = vq->desc_state[i].data;
> - detach_buf(vq, i, ctx);
> + detach_buf_split(vq, i, ctx);
> vq->last_used_idx++;
> /* If we expect an interrupt for the next entry, tell host
> * by writing event index and flush out the write before
> @@ -754,6 +1098,87 @@ void *virtqueue_get_buf_ctx(struct virtqueue *_vq, unsigned int *len,
> END_USE(vq);
> return ret;
> }
> +
> +void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq, unsigned int *len,
> + void **ctx)
> +{
> + struct vring_virtqueue *vq = to_vvq(_vq);
> + void *ret;
> + unsigned int i;
> + u16 last_used;
> +
> + START_USE(vq);
> +
> + if (unlikely(vq->broken)) {
> + END_USE(vq);
> + return NULL;
> + }
> +
> + if (!more_used(vq)) {
> + pr_debug("No more buffers in queue\n");
> + END_USE(vq);
> + return NULL;
> + }
> +
> + /* Only get used array entries after they have been exposed by host. */
> + virtio_rmb(vq->weak_barriers);
> +
> + last_used = vq->last_used_idx;
> +
> + i = virtio32_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(i >= vq->vring_packed.num)) {
> + BAD_RING(vq, "id %u out of range\n", i);
> + return NULL;
> + }
> + if (unlikely(!vq->desc_state[i].data)) {
> + BAD_RING(vq, "id %u is not a head!\n", i);
> + return NULL;
> + }
> +
> + /* detach_buf_packed clears data, so grab it now. */
> + ret = vq->desc_state[i].data;
> + detach_buf_packed(vq, i, ctx);
> +
> + vq->last_used_idx += vq->desc_state[i].num;
> + if (vq->last_used_idx >= vq->vring_packed.num)
> + vq->last_used_idx %= vq->vring_packed.num;

'-=' should be sufficient here?

> +
> + // FIXME: implement the desc event support
> +
> +#ifdef DEBUG
> + vq->last_add_time_valid = false;
> +#endif
> +
> + END_USE(vq);
> + return ret;
> +}
> +
> +/**
> + * virtqueue_get_buf - get the next used buffer
> + * @vq: the struct virtqueue we're talking about.
> + * @len: the length written into the buffer
> + *
> + * If the device wrote data into the buffer, @len will be set to the
> + * amount written. This means you don't need to clear the buffer
> + * beforehand to ensure there's no data leakage in the case of short
> + * writes.
> + *
> + * Caller must ensure we don't call this with other virtqueue
> + * operations at the same time (except where noted).
> + *
> + * Returns NULL if there are no used buffers, or the "data" token
> + * handed to virtqueue_add_*().
> + */
> +void *virtqueue_get_buf_ctx(struct virtqueue *_vq, unsigned int *len,
> + void **ctx)
> +{
> + struct vring_virtqueue *vq = to_vvq(_vq);
> +
> + return vq->packed ? virtqueue_get_buf_ctx_packed(_vq, len, ctx) :
> + virtqueue_get_buf_ctx_split(_vq, len, ctx);
> +}
> EXPORT_SYMBOL_GPL(virtqueue_get_buf_ctx);
>
> void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)
> @@ -761,6 +1186,24 @@ void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)
> return virtqueue_get_buf_ctx(_vq, len, NULL);
> }
> EXPORT_SYMBOL_GPL(virtqueue_get_buf);
> +
> +static void virtqueue_disable_cb_split(struct virtqueue *_vq)
> +{
> + struct vring_virtqueue *vq = to_vvq(_vq);
> +
> + if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
> + vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
> + if (!vq->event)
> + vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev,
> + vq->avail_flags_shadow);
> + }
> +}
> +
> +static void virtqueue_disable_cb_packed(struct virtqueue *_vq)
> +{
> + // FIXME: to be implemented
> +}
> +
> /**
> * virtqueue_disable_cb - disable callbacks
> * @vq: the struct virtqueue we're talking about.
> @@ -774,12 +1217,10 @@ void virtqueue_disable_cb(struct virtqueue *_vq)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> - if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
> - vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
> - if (!vq->event)
> - vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow);
> - }
> -
> + if (vq->packed)
> + virtqueue_disable_cb_packed(_vq);
> + else
> + virtqueue_disable_cb_split(_vq);
> }
> EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
>
> @@ -802,6 +1243,12 @@ unsigned virtqueue_enable_cb_prepare(struct virtqueue *_vq)
>
> START_USE(vq);
>
> + if (vq->packed) {
> + // FIXME: to be implemented
> + last_used_idx = vq->last_used_idx;
> + goto out;
> + }
> +
> /* We optimistically turn back on interrupts, then check if there was
> * more to do. */
> /* Depending on the VIRTIO_RING_F_EVENT_IDX feature, we need to
> @@ -813,6 +1260,7 @@ unsigned virtqueue_enable_cb_prepare(struct virtqueue *_vq)
> vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow);
> }
> vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev, last_used_idx = vq->last_used_idx);
> +out:
> END_USE(vq);
> return last_used_idx;
> }
> @@ -832,6 +1280,12 @@ bool virtqueue_poll(struct virtqueue *_vq, unsigned last_used_idx)
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> virtio_mb(vq->weak_barriers);
> + if (vq->packed) {
> + u16 flags = virtio16_to_cpu(vq->vq.vdev,
> + vq->vring_packed.desc[last_used_idx].flags);
> + return !(flags & VRING_DESC_F_AVAIL(1)) ==
> + !(flags & VRING_DESC_F_USED(1));
> + }
> return (u16)last_used_idx != virtio16_to_cpu(_vq->vdev, vq->vring.used->idx);
> }
> EXPORT_SYMBOL_GPL(virtqueue_poll);
> @@ -874,6 +1328,11 @@ bool virtqueue_enable_cb_delayed(struct virtqueue *_vq)
>
> START_USE(vq);
>
> + if (vq->packed) {
> + // FIXME: to be implemented
> + goto out;
> + }
> +
> /* We optimistically turn back on interrupts, then check if there was
> * more to do. */
> /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to
> @@ -896,6 +1355,7 @@ bool virtqueue_enable_cb_delayed(struct virtqueue *_vq)
> return false;
> }
>
> +out:
> END_USE(vq);
> return true;
> }
> @@ -922,14 +1382,20 @@ void *virtqueue_detach_unused_buf(struct virtqueue *_vq)
> continue;
> /* detach_buf clears data, so grab it now. */
> buf = vq->desc_state[i].data;
> - detach_buf(vq, i, NULL);
> - vq->avail_idx_shadow--;
> - vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev, vq->avail_idx_shadow);
> + if (vq->packed)
> + detach_buf_packed(vq, i, NULL);
> + else {
> + detach_buf_split(vq, i, NULL);
> + vq->avail_idx_shadow--;
> + vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev,
> + vq->avail_idx_shadow);
> + }
> END_USE(vq);
> return buf;
> }
> /* That should have freed everything. */
> - BUG_ON(vq->vq.num_free != vq->vring.num);
> + BUG_ON(vq->vq.num_free != (vq->packed ? vq->vring_packed.num :
> + vq->vring.num));
>
> END_USE(vq);
> return NULL;
> @@ -957,7 +1423,8 @@ irqreturn_t vring_interrupt(int irq, void *_vq)
> EXPORT_SYMBOL_GPL(vring_interrupt);
>
> struct virtqueue *__vring_new_virtqueue(unsigned int index,
> - struct vring vring,
> + union vring_union vring,
> + bool packed,
> struct virtio_device *vdev,
> bool weak_barriers,
> bool context,
> @@ -965,19 +1432,20 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
> void (*callback)(struct virtqueue *),
> const char *name)
> {
> - unsigned int i;
> + unsigned int num, i;
> struct vring_virtqueue *vq;
>
> - vq = kmalloc(sizeof(*vq) + vring.num * sizeof(struct vring_desc_state),
> + num = packed ? vring.vring_packed.num : vring.vring_split.num;
> +
> + vq = kmalloc(sizeof(*vq) + num * sizeof(struct vring_desc_state),
> GFP_KERNEL);
> if (!vq)
> return NULL;
>
> - vq->vring = vring;
> vq->vq.callback = callback;
> vq->vq.vdev = vdev;
> vq->vq.name = name;
> - vq->vq.num_free = vring.num;
> + vq->vq.num_free = num;
> vq->vq.index = index;
> vq->we_own_ring = false;
> vq->queue_dma_addr = 0;
> @@ -986,9 +1454,8 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
> vq->weak_barriers = weak_barriers;
> vq->broken = false;
> vq->last_used_idx = 0;
> - vq->avail_flags_shadow = 0;
> - vq->avail_idx_shadow = 0;
> vq->num_added = 0;
> + vq->packed = packed;
> list_add_tail(&vq->vq.list, &vdev->vqs);
> #ifdef DEBUG
> vq->in_use = false;
> @@ -999,18 +1466,41 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
> !context;
> vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
>
> + if (vq->packed) {
> + vq->vring_packed = vring.vring_packed;
> + vq->free_head = 0;
> + vq->wrap_counter = 1;
> +
> +#if 0
> + vq->chaining = virtio_has_feature(vdev,
> + VIRTIO_RING_F_LIST_DESC);
> +#else
> + vq->chaining = true;

Looks like in V10 there's no F_LIST_DESC.

> +#endif
> + } else {
> + vq->vring = vring.vring_split;
> + vq->avail_flags_shadow = 0;
> + vq->avail_idx_shadow = 0;
> +
> + /* Put everything in free lists. */
> + vq->free_head = 0;
> + for (i = 0; i < num-1; i++)
> + vq->vring.desc[i].next = cpu_to_virtio16(vdev, i + 1);
> + }
> +
> /* No callback? Tell other side not to bother us. */
> if (!callback) {
> - vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
> - if (!vq->event)
> - vq->vring.avail->flags = cpu_to_virtio16(vdev, vq->avail_flags_shadow);
> + if (packed) {
> + // FIXME: to be implemented
> + } else {
> + vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
> + if (!vq->event)
> + vq->vring.avail->flags = cpu_to_virtio16(vdev,
> + vq->avail_flags_shadow);
> + }
> }
>
> - /* 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);
> - memset(vq->desc_state, 0, vring.num * sizeof(struct vring_desc_state));
> + memset(vq->desc_state, 0, num * sizeof(struct vring_desc_state));
>
> return &vq->vq;
> }
> @@ -1058,6 +1548,14 @@ static void vring_free_queue(struct virtio_device *vdev, size_t size,
> }
> }
>
> +static inline int
> +__vring_size(unsigned int num, unsigned long align, bool packed)
> +{
> + if (packed)
> + return vring_packed_size(num, align);
> + return vring_size(num, align);
> +}
> +
> struct virtqueue *vring_create_virtqueue(
> unsigned int index,
> unsigned int num,
> @@ -1074,7 +1572,8 @@ struct virtqueue *vring_create_virtqueue(
> void *queue = NULL;
> dma_addr_t dma_addr;
> size_t queue_size_in_bytes;
> - struct vring vring;
> + union vring_union vring;
> + bool packed;
>
> /* We assume num is a power of 2. */
> if (num & (num - 1)) {
> @@ -1082,9 +1581,13 @@ struct virtqueue *vring_create_virtqueue(
> return NULL;
> }
>
> + packed = virtio_has_feature(vdev, VIRTIO_F_RING_PACKED);
> +
> /* TODO: allocate each queue chunk individually */
> - for (; num && vring_size(num, vring_align) > PAGE_SIZE; num /= 2) {
> - queue = vring_alloc_queue(vdev, vring_size(num, vring_align),
> + for (; num && __vring_size(num, vring_align, packed) > PAGE_SIZE;
> + num /= 2) {
> + queue = vring_alloc_queue(vdev, __vring_size(num, vring_align,
> + packed),
> &dma_addr,
> GFP_KERNEL|__GFP_NOWARN|__GFP_ZERO);
> if (queue)
> @@ -1096,17 +1599,21 @@ struct virtqueue *vring_create_virtqueue(
>
> if (!queue) {
> /* Try to get a single page. You are my only hope! */
> - queue = vring_alloc_queue(vdev, vring_size(num, vring_align),
> + queue = vring_alloc_queue(vdev, __vring_size(num, vring_align,
> + packed),
> &dma_addr, GFP_KERNEL|__GFP_ZERO);
> }
> if (!queue)
> return NULL;
>
> - queue_size_in_bytes = vring_size(num, vring_align);
> - vring_init(&vring, num, queue, vring_align);
> + queue_size_in_bytes = __vring_size(num, vring_align, packed);
> + if (packed)
> + vring_packed_init(&vring.vring_packed, num, queue, vring_align);
> + else
> + vring_init(&vring.vring_split, num, queue, vring_align);

Let's rename vring_init to vring_init_split() like other helpers?

>
> - vq = __vring_new_virtqueue(index, vring, vdev, weak_barriers, context,
> - notify, callback, name);
> + vq = __vring_new_virtqueue(index, vring, packed, vdev, weak_barriers,
> + context, notify, callback, name);
> if (!vq) {
> vring_free_queue(vdev, queue_size_in_bytes, queue,
> dma_addr);
> @@ -1132,10 +1639,17 @@ struct virtqueue *vring_new_virtqueue(unsigned int index,
> void (*callback)(struct virtqueue *vq),
> const char *name)
> {
> - struct vring vring;
> - vring_init(&vring, num, pages, vring_align);
> - return __vring_new_virtqueue(index, vring, vdev, weak_barriers, context,
> - notify, callback, name);
> + union vring_union vring;
> + bool packed;
> +
> + packed = virtio_has_feature(vdev, VIRTIO_F_RING_PACKED);
> + if (packed)
> + vring_packed_init(&vring.vring_packed, num, pages, vring_align);
> + else
> + vring_init(&vring.vring_split, num, pages, vring_align);
> +
> + return __vring_new_virtqueue(index, vring, packed, vdev, weak_barriers,
> + context, notify, callback, name);
> }
> EXPORT_SYMBOL_GPL(vring_new_virtqueue);
>
> @@ -1145,7 +1659,9 @@ void vring_del_virtqueue(struct virtqueue *_vq)
>
> if (vq->we_own_ring) {
> vring_free_queue(vq->vq.vdev, vq->queue_size_in_bytes,
> - vq->vring.desc, vq->queue_dma_addr);
> + vq->packed ? (void *)vq->vring_packed.desc :
> + (void *)vq->vring.desc,
> + vq->queue_dma_addr);
> }
> list_del(&_vq->list);
> kfree(vq);
> @@ -1159,14 +1675,18 @@ void vring_transport_features(struct virtio_device *vdev)
>
> for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
> switch (i) {
> +#if 0 // FIXME: to be implemented
> case VIRTIO_RING_F_INDIRECT_DESC:
> break;
> +#endif
> case VIRTIO_RING_F_EVENT_IDX:
> break;
> case VIRTIO_F_VERSION_1:
> break;
> case VIRTIO_F_IOMMU_PLATFORM:
> break;
> + case VIRTIO_F_RING_PACKED:
> + break;
> default:
> /* We don't understand this bit. */
> __virtio_clear_bit(vdev, i);
> @@ -1187,7 +1707,7 @@ unsigned int virtqueue_get_vring_size(struct virtqueue *_vq)
>
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> - return vq->vring.num;
> + return vq->packed ? vq->vring_packed.num : vq->vring.num;
> }
> EXPORT_SYMBOL_GPL(virtqueue_get_vring_size);
>
> @@ -1224,6 +1744,7 @@ dma_addr_t virtqueue_get_desc_addr(struct virtqueue *_vq)
> }
> EXPORT_SYMBOL_GPL(virtqueue_get_desc_addr);
>
> +/* Only available for split ring */

Interesting, I think we need this for correctly configure pci. e.g in
setup_vq()?

> dma_addr_t virtqueue_get_avail_addr(struct virtqueue *_vq)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
> @@ -1235,6 +1756,7 @@ dma_addr_t virtqueue_get_avail_addr(struct virtqueue *_vq)
> }
> EXPORT_SYMBOL_GPL(virtqueue_get_avail_addr);
>
> +/* Only available for split ring */
> dma_addr_t virtqueue_get_used_addr(struct virtqueue *_vq)

Maybe it's better to rename this to get_device_addr().

Thanks

> {
> struct vring_virtqueue *vq = to_vvq(_vq);
> @@ -1246,6 +1768,7 @@ dma_addr_t virtqueue_get_used_addr(struct virtqueue *_vq)
> }
> EXPORT_SYMBOL_GPL(virtqueue_get_used_addr);
>
> +/* Only available for split ring */
> const struct vring *virtqueue_get_vring(struct virtqueue *vq)
> {
> return &to_vvq(vq)->vring;
> diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
> index bbf32524ab27..a0075894ad16 100644
> --- a/include/linux/virtio_ring.h
> +++ b/include/linux/virtio_ring.h
> @@ -60,6 +60,11 @@ static inline void virtio_store_mb(bool weak_barriers,
> struct virtio_device;
> struct virtqueue;
>
> +union vring_union {
> + struct vring vring_split;
> + struct vring_packed vring_packed;
> +};
> +
> /*
> * Creates a virtqueue and allocates the descriptor ring. If
> * may_reduce_num is set, then this may allocate a smaller ring than
> @@ -79,7 +84,8 @@ struct virtqueue *vring_create_virtqueue(unsigned int index,
>
> /* Creates a virtqueue with a custom layout. */
> struct virtqueue *__vring_new_virtqueue(unsigned int index,
> - struct vring vring,
> + union vring_union vring,
> + bool packed,
> struct virtio_device *vdev,
> bool weak_barriers,
> bool ctx,

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