On Tue, 5 Dec 2023 15:12:03 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote:
> On Mon, Dec 4, 2023 at 3:23 PM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote:
> >
> > introduce virtqueue_get_buf_ctx_dma() to collect the dma info when
> > get buf from virtio core for premapped mode.
> >
> > If the virtio queue is premapped mode, the virtio-net send buf may
> > have many desc. Every desc dma address need to be unmap. So here we
> > introduce a new helper to collect the dma address of the buffer from
> > the virtio core.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> > ---
> > drivers/virtio/virtio_ring.c | 157 +++++++++++++++++++++++------------
> > include/linux/virtio.h | 16 ++++
> > 2 files changed, 121 insertions(+), 52 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > index 51d8f3299c10..103d181f05bb 100644
> > --- a/drivers/virtio/virtio_ring.c
> > +++ b/drivers/virtio/virtio_ring.c
> > @@ -362,6 +362,26 @@ static struct device *vring_dma_dev(const struct vring_virtqueue *vq)
> > return vq->dma_dev;
> > }
> >
> > +static void collect_dma_info(const struct vring_virtqueue *vq,
>
> Not a native speaker, but it looks to me like "get_dma_info" is better here.
get_dma_info?
This function collect the dma info to the dma array.
Not to the dirver. So do you also think "get_dma_info" is better?
>
> > + struct virtio_dma_head *dma,
> > + dma_addr_t addr, unsigned int length)
> > +{
> > + if (WARN_ON_ONCE(!dma))
> > + return;
>
> So all the callers did:
>
> if (!vq->do_unmap)
> collect_dma_info()
>
> It's a strong hint that we should move the vq->do_unmap inside
> collect_dma_info()?
No,
vq->do_unmap affects the logic of caller.
Such as:
if (!vq->do_unmap) {
collect_dma_info(vq, dma, le64_to_cpu(desc->addr), le32_to_cpu(desc->len));
return;
}
So we should move it to this function.
>
> > +
> > + if (unlikely(dma->next >= dma->num)) {
> > + dev_warn_once(&vq->vq.vdev->dev,
> > + "premapped vq: collect dma miss: %pad %u\n",
> > + &addr, length);
>
> Let's use BAD_RING() for consistency.
>
> Btw, the message seems ambiguous here.
Will fix.
>
> > + return;
> > + }
> > +
> > + dma->items[dma->next].addr = addr;
> > + dma->items[dma->next].length = length;
> > +
> > + ++dma->next;
> > +}
> > +
> > /* Map one sg entry. */
> > static int vring_map_one_sg(const struct vring_virtqueue *vq, struct scatterlist *sg,
> > enum dma_data_direction direction, dma_addr_t *addr)
> > @@ -441,12 +461,17 @@ static void virtqueue_init(struct vring_virtqueue *vq, u32 num)
> > */
> >
> > static void vring_unmap_one_split_indirect(const struct vring_virtqueue *vq,
> > - const struct vring_desc *desc)
> > + const struct vring_desc *desc,
> > + struct virtio_dma_head *dma)
> > {
> > u16 flags;
> >
> > - if (!vq->do_unmap)
> > + if (!vq->do_unmap) {
> > + collect_dma_info(vq, dma,
> > + virtio64_to_cpu(vq->vq.vdev, desc->addr),
> > + virtio32_to_cpu(vq->vq.vdev, desc->len));
> > return;
> > + }
> >
> > flags = virtio16_to_cpu(vq->vq.vdev, desc->flags);
> >
> > @@ -458,7 +483,7 @@ static void vring_unmap_one_split_indirect(const struct vring_virtqueue *vq,
> > }
> >
> > static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq,
> > - unsigned int i)
> > + unsigned int i, struct virtio_dma_head *dma)
> > {
> > struct vring_desc_extra *extra = vq->split.desc_extra;
> > u16 flags;
> > @@ -466,18 +491,15 @@ static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq,
> > flags = extra[i].flags;
> >
> > if (flags & VRING_DESC_F_INDIRECT) {
> > - if (!vq->use_dma_api)
> > - goto out;
> > -
> > - dma_unmap_single(vring_dma_dev(vq),
> > - extra[i].addr,
> > - extra[i].len,
> > - (flags & VRING_DESC_F_WRITE) ?
> > - DMA_FROM_DEVICE : DMA_TO_DEVICE);
> > + if (vq->use_dma_api)
> > + dma_unmap_single(vring_dma_dev(vq),
> > + extra[i].addr,
> > + extra[i].len,
> > + (flags & VRING_DESC_F_WRITE) ?
> > + DMA_FROM_DEVICE : DMA_TO_DEVICE);
> > + } else if (!vq->do_unmap) {
> > + collect_dma_info(vq, dma, extra[i].addr, extra[i].len);
> > } else {
> > - if (!vq->do_unmap)
> > - goto out;
> > -
> > dma_unmap_page(vring_dma_dev(vq),
> > extra[i].addr,
> > extra[i].len,
> > @@ -485,7 +507,6 @@ static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq,
> > DMA_FROM_DEVICE : DMA_TO_DEVICE);
> > }
> >
> > -out:
> > return extra[i].next;
> > }
> >
> > @@ -717,10 +738,10 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
> > if (i == err_idx)
> > break;
> > if (indirect) {
> > - vring_unmap_one_split_indirect(vq, &desc[i]);
> > + vring_unmap_one_split_indirect(vq, &desc[i], NULL);
>
> So this will trigger the WARN_ON_ONCE() in collect_dma_info()?
I thought about this.
But rethink it, I found I missed one case.
Here is not called, when the vq is premapeed mode.
But, if the use_dma_api is false, this is called.
Will fix it.
>
> > i = virtio16_to_cpu(_vq->vdev, desc[i].next);
> > } else
> > - i = vring_unmap_one_split(vq, i);
> > + i = vring_unmap_one_split(vq, i, NULL);
> > }
> >
> > free_indirect:
> > @@ -763,7 +784,7 @@ static bool virtqueue_kick_prepare_split(struct virtqueue *_vq)
> > }
> >
> > static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
> > - void **ctx)
> > + struct virtio_dma_head *dma, void **ctx)
> > {
> > unsigned int i, j;
> > __virtio16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
> > @@ -775,12 +796,12 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
> > i = head;
> >
> > while (vq->split.vring.desc[i].flags & nextflag) {
> > - vring_unmap_one_split(vq, i);
> > + vring_unmap_one_split(vq, i, dma);
> > i = vq->split.desc_extra[i].next;
> > vq->vq.num_free++;
> > }
> >
> > - vring_unmap_one_split(vq, i);
> > + vring_unmap_one_split(vq, i, dma);
> > vq->split.desc_extra[i].next = vq->free_head;
> > vq->free_head = head;
> >
> > @@ -802,10 +823,8 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
> > VRING_DESC_F_INDIRECT));
> > BUG_ON(len == 0 || len % sizeof(struct vring_desc));
> >
> > - if (vq->do_unmap) {
> > - for (j = 0; j < len / sizeof(struct vring_desc); j++)
> > - vring_unmap_one_split_indirect(vq, &indir_desc[j]);
> > - }
> > + for (j = 0; j < len / sizeof(struct vring_desc); j++)
> > + vring_unmap_one_split_indirect(vq, &indir_desc[j], dma);
> >
> > kfree(indir_desc);
> > vq->split.desc_state[head].indir_desc = NULL;
> > @@ -822,6 +841,7 @@ static bool more_used_split(const struct vring_virtqueue *vq)
> >
> > static void *virtqueue_get_buf_ctx_split(struct virtqueue *_vq,
> > unsigned int *len,
> > + struct virtio_dma_head *dma,
> > void **ctx)
> > {
> > struct vring_virtqueue *vq = to_vvq(_vq);
> > @@ -862,7 +882,7 @@ static void *virtqueue_get_buf_ctx_split(struct virtqueue *_vq,
> >
> > /* detach_buf_split clears data, so grab it now. */
> > ret = vq->split.desc_state[i].data;
> > - detach_buf_split(vq, i, ctx);
> > + detach_buf_split(vq, i, dma, 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
> > @@ -984,7 +1004,7 @@ static void *virtqueue_detach_unused_buf_split(struct virtqueue *_vq)
> > continue;
> > /* detach_buf_split clears data, so grab it now. */
> > buf = vq->split.desc_state[i].data;
> > - detach_buf_split(vq, i, NULL);
> > + detach_buf_split(vq, i, NULL, NULL);
> > vq->split.avail_idx_shadow--;
> > vq->split.vring.avail->idx = cpu_to_virtio16(_vq->vdev,
> > vq->split.avail_idx_shadow);
> > @@ -1221,7 +1241,8 @@ 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,
> > + struct virtio_dma_head *dma)
> > {
> > u16 flags;
> >
> > @@ -1235,10 +1256,9 @@ static void vring_unmap_extra_packed(const struct vring_virtqueue *vq,
> > extra->addr, extra->len,
> > (flags & VRING_DESC_F_WRITE) ?
> > DMA_FROM_DEVICE : DMA_TO_DEVICE);
> > + } else if (!vq->do_unmap) {
> > + collect_dma_info(vq, dma, extra->addr, extra->len);
> > } else {
> > - if (!vq->do_unmap)
> > - return;
> > -
> > dma_unmap_page(vring_dma_dev(vq),
> > extra->addr, extra->len,
> > (flags & VRING_DESC_F_WRITE) ?
> > @@ -1247,12 +1267,15 @@ 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)
> > + const struct vring_packed_desc *desc,
> > + struct virtio_dma_head *dma)
> > {
> > u16 flags;
> >
> > - if (!vq->do_unmap)
> > + if (!vq->do_unmap) {
> > + collect_dma_info(vq, dma, le64_to_cpu(desc->addr), le32_to_cpu(desc->len));
> > return;
> > + }
> >
> > flags = le16_to_cpu(desc->flags);
> >
> > @@ -1389,7 +1412,7 @@ 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_desc_packed(vq, &desc[i], NULL);
> >
> > free_desc:
> > kfree(desc);
> > @@ -1539,7 +1562,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
> > for (n = 0; n < total_sg; n++) {
> > if (i == err_idx)
> > break;
> > - vring_unmap_extra_packed(vq, &vq->packed.desc_extra[curr]);
> > + vring_unmap_extra_packed(vq, &vq->packed.desc_extra[curr], NULL);
> > curr = vq->packed.desc_extra[curr].next;
> > i++;
> > if (i >= vq->packed.vring.num)
> > @@ -1600,7 +1623,9 @@ static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq)
> > }
> >
> > static void detach_buf_packed(struct vring_virtqueue *vq,
> > - unsigned int id, void **ctx)
> > + unsigned int id,
> > + struct virtio_dma_head *dma,
> > + void **ctx)
> > {
> > struct vring_desc_state_packed *state = NULL;
> > struct vring_packed_desc *desc;
> > @@ -1615,13 +1640,10 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
> > vq->free_head = id;
> > vq->vq.num_free += state->num;
> >
> > - if (unlikely(vq->do_unmap)) {
> > - curr = id;
> > - for (i = 0; i < state->num; i++) {
> > - vring_unmap_extra_packed(vq,
> > - &vq->packed.desc_extra[curr]);
> > - curr = vq->packed.desc_extra[curr].next;
> > - }
> > + curr = id;
> > + for (i = 0; i < state->num; i++) {
> > + vring_unmap_extra_packed(vq, &vq->packed.desc_extra[curr], dma);
> > + curr = vq->packed.desc_extra[curr].next;
>
> I wonder if !dma && vq->do_unmap is valid, we need to document it somewhere.
Yes, it can be valid.
>
> And we can keep the unlikely() optimization as is.
I don't think there is a high probability for do_unmap. I don't think it's
necessary to keep the unlikely().
>
>
> > }
> >
> > if (vq->indirect) {
> > @@ -1632,12 +1654,9 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
> > if (!desc)
> > return;
> >
> > - if (vq->do_unmap) {
> > - 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]);
> > - }
> > + 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], dma);
> > kfree(desc);
> > state->indir_desc = NULL;
> > } else if (ctx) {
> > @@ -1672,6 +1691,7 @@ static bool more_used_packed(const struct vring_virtqueue *vq)
> >
> > static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq,
> > unsigned int *len,
> > + struct virtio_dma_head *dma,
> > void **ctx)
> > {
> > struct vring_virtqueue *vq = to_vvq(_vq);
> > @@ -1712,7 +1732,7 @@ static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq,
> >
> > /* detach_buf_packed clears data, so grab it now. */
> > ret = vq->packed.desc_state[id].data;
> > - detach_buf_packed(vq, id, ctx);
> > + detach_buf_packed(vq, id, dma, ctx);
> >
> > last_used += vq->packed.desc_state[id].num;
> > if (unlikely(last_used >= vq->packed.vring.num)) {
> > @@ -1877,7 +1897,7 @@ static void *virtqueue_detach_unused_buf_packed(struct virtqueue *_vq)
> > continue;
> > /* detach_buf clears data, so grab it now. */
> > buf = vq->packed.desc_state[i].data;
> > - detach_buf_packed(vq, i, NULL);
> > + detach_buf_packed(vq, i, NULL, NULL);
> > END_USE(vq);
> > return buf;
> > }
> > @@ -2417,11 +2437,44 @@ void *virtqueue_get_buf_ctx(struct virtqueue *_vq, unsigned int *len,
> > {
> > struct vring_virtqueue *vq = to_vvq(_vq);
> >
> > - return vq->packed_ring ? virtqueue_get_buf_ctx_packed(_vq, len, ctx) :
> > - virtqueue_get_buf_ctx_split(_vq, len, ctx);
> > + return vq->packed_ring ? virtqueue_get_buf_ctx_packed(_vq, len, NULL, ctx) :
> > + virtqueue_get_buf_ctx_split(_vq, len, NULL, ctx);
> > }
> > EXPORT_SYMBOL_GPL(virtqueue_get_buf_ctx);
> >
> > +/**
> > + * virtqueue_get_buf_ctx_dma - get the next used buffer with the dma info
> > + * @_vq: the struct virtqueue we're talking about.
> > + * @len: the length written into the buffer
> > + * @dma: the head of the array to store the dma info
> > + * @ctx: extra context for the token
> > + *
> > + * 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).
> > + *
> > + * We store the dma info of every descriptor of this buf to the dma->items
> > + * array. If the array size is too small, some dma info may be missed, so
> > + * the caller must ensure the array is enough.
>
> large enough?
Will fix.
>
> > The dma->next is the out value
> > + * to the caller,
>
> What do you mean by "out value to the caller" ?
The caller know how many items are used by this dma->next.
This is out value to the caller.
Thanks.
>
> Thanks
>
>
> > indicates the num of the used items.
> > + *
> > + * Returns NULL if there are no used buffers, or the "data" token
> > + * handed to virtqueue_add_*().
> > + */
> > +void *virtqueue_get_buf_ctx_dma(struct virtqueue *_vq, unsigned int *len,
> > + struct virtio_dma_head *dma, void **ctx)
> > +{
> > + struct vring_virtqueue *vq = to_vvq(_vq);
> > +
> > + return vq->packed_ring ? virtqueue_get_buf_ctx_packed(_vq, len, dma, ctx) :
> > + virtqueue_get_buf_ctx_split(_vq, len, dma, ctx);
> > +}
> > +EXPORT_SYMBOL_GPL(virtqueue_get_buf_ctx_dma);
> > +
> > void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)
> > {
> > return virtqueue_get_buf_ctx(_vq, len, NULL);
> > diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> > index 4cc614a38376..572aecec205b 100644
> > --- a/include/linux/virtio.h
> > +++ b/include/linux/virtio.h
> > @@ -75,6 +75,22 @@ void *virtqueue_get_buf(struct virtqueue *vq, unsigned int *len);
> > void *virtqueue_get_buf_ctx(struct virtqueue *vq, unsigned int *len,
> > void **ctx);
> >
> > +struct virtio_dma_item {
> > + dma_addr_t addr;
> > + unsigned int length;
> > +};
> > +
> > +struct virtio_dma_head {
> > + /* total num of items. */
> > + u16 num;
> > + /* point to the next item to store dma info. */
> > + u16 next;
> > + struct virtio_dma_item items[];
> > +};
> > +
> > +void *virtqueue_get_buf_ctx_dma(struct virtqueue *_vq, unsigned int *len,
> > + struct virtio_dma_head *dma, void **ctx);
> > +
> > void virtqueue_disable_cb(struct virtqueue *vq);
> >
> > bool virtqueue_enable_cb(struct virtqueue *vq);
> > --
> > 2.32.0.3.g01195cf9f
> >
>
