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    Subject[PATCH RFC v5 02/13] vhost: use batched version by default
    As testing shows no performance change, switch to that now.

    Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
    Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
    Link: https://lore.kernel.org/r/20200401183118.8334-3-eperezma@redhat.com
    Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
    ---
    drivers/vhost/vhost.c | 251 +-----------------------------------------
    drivers/vhost/vhost.h | 4 -
    2 files changed, 2 insertions(+), 253 deletions(-)

    diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
    index e682ed551587..33a72edb3ccd 100644
    --- a/drivers/vhost/vhost.c
    +++ b/drivers/vhost/vhost.c
    @@ -2078,253 +2078,6 @@ static unsigned next_desc(struct vhost_virtqueue *vq, struct vring_desc *desc)
    return next;
    }

    -static int get_indirect(struct vhost_virtqueue *vq,
    - struct iovec iov[], unsigned int iov_size,
    - unsigned int *out_num, unsigned int *in_num,
    - struct vhost_log *log, unsigned int *log_num,
    - struct vring_desc *indirect)
    -{
    - struct vring_desc desc;
    - unsigned int i = 0, count, found = 0;
    - u32 len = vhost32_to_cpu(vq, indirect->len);
    - struct iov_iter from;
    - int ret, access;
    -
    - /* Sanity check */
    - if (unlikely(len % sizeof desc)) {
    - vq_err(vq, "Invalid length in indirect descriptor: "
    - "len 0x%llx not multiple of 0x%zx\n",
    - (unsigned long long)len,
    - sizeof desc);
    - return -EINVAL;
    - }
    -
    - ret = translate_desc(vq, vhost64_to_cpu(vq, indirect->addr), len, vq->indirect,
    - UIO_MAXIOV, VHOST_ACCESS_RO);
    - if (unlikely(ret < 0)) {
    - if (ret != -EAGAIN)
    - vq_err(vq, "Translation failure %d in indirect.\n", ret);
    - return ret;
    - }
    - iov_iter_init(&from, READ, vq->indirect, ret, len);
    -
    - /* We will use the result as an address to read from, so most
    - * architectures only need a compiler barrier here. */
    - read_barrier_depends();
    -
    - count = len / sizeof desc;
    - /* Buffers are chained via a 16 bit next field, so
    - * we can have at most 2^16 of these. */
    - if (unlikely(count > USHRT_MAX + 1)) {
    - vq_err(vq, "Indirect buffer length too big: %d\n",
    - indirect->len);
    - return -E2BIG;
    - }
    -
    - do {
    - unsigned iov_count = *in_num + *out_num;
    - if (unlikely(++found > count)) {
    - vq_err(vq, "Loop detected: last one at %u "
    - "indirect size %u\n",
    - i, count);
    - return -EINVAL;
    - }
    - if (unlikely(!copy_from_iter_full(&desc, sizeof(desc), &from))) {
    - vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
    - i, (size_t)vhost64_to_cpu(vq, indirect->addr) + i * sizeof desc);
    - return -EINVAL;
    - }
    - if (unlikely(desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT))) {
    - vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
    - i, (size_t)vhost64_to_cpu(vq, indirect->addr) + i * sizeof desc);
    - return -EINVAL;
    - }
    -
    - if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE))
    - access = VHOST_ACCESS_WO;
    - else
    - access = VHOST_ACCESS_RO;
    -
    - ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr),
    - vhost32_to_cpu(vq, desc.len), iov + iov_count,
    - iov_size - iov_count, access);
    - if (unlikely(ret < 0)) {
    - if (ret != -EAGAIN)
    - vq_err(vq, "Translation failure %d indirect idx %d\n",
    - ret, i);
    - return ret;
    - }
    - /* If this is an input descriptor, increment that count. */
    - if (access == VHOST_ACCESS_WO) {
    - *in_num += ret;
    - if (unlikely(log && ret)) {
    - log[*log_num].addr = vhost64_to_cpu(vq, desc.addr);
    - log[*log_num].len = vhost32_to_cpu(vq, desc.len);
    - ++*log_num;
    - }
    - } else {
    - /* If it's an output descriptor, they're all supposed
    - * to come before any input descriptors. */
    - if (unlikely(*in_num)) {
    - vq_err(vq, "Indirect descriptor "
    - "has out after in: idx %d\n", i);
    - return -EINVAL;
    - }
    - *out_num += ret;
    - }
    - } while ((i = next_desc(vq, &desc)) != -1);
    - return 0;
    -}
    -
    -/* This looks in the virtqueue and for the first available buffer, and converts
    - * it to an iovec for convenient access. Since descriptors consist of some
    - * number of output then some number of input descriptors, it's actually two
    - * iovecs, but we pack them into one and note how many of each there were.
    - *
    - * This function returns the descriptor number found, or vq->num (which is
    - * never a valid descriptor number) if none was found. A negative code is
    - * returned on error. */
    -int vhost_get_vq_desc(struct vhost_virtqueue *vq,
    - struct iovec iov[], unsigned int iov_size,
    - unsigned int *out_num, unsigned int *in_num,
    - struct vhost_log *log, unsigned int *log_num)
    -{
    - struct vring_desc desc;
    - unsigned int i, head, found = 0;
    - u16 last_avail_idx;
    - __virtio16 avail_idx;
    - __virtio16 ring_head;
    - int ret, access;
    -
    - /* Check it isn't doing very strange things with descriptor numbers. */
    - last_avail_idx = vq->last_avail_idx;
    -
    - if (vq->avail_idx == vq->last_avail_idx) {
    - if (unlikely(vhost_get_avail_idx(vq, &avail_idx))) {
    - vq_err(vq, "Failed to access avail idx at %p\n",
    - &vq->avail->idx);
    - return -EFAULT;
    - }
    - vq->avail_idx = vhost16_to_cpu(vq, avail_idx);
    -
    - if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
    - vq_err(vq, "Guest moved used index from %u to %u",
    - last_avail_idx, vq->avail_idx);
    - return -EFAULT;
    - }
    -
    - /* If there's nothing new since last we looked, return
    - * invalid.
    - */
    - if (vq->avail_idx == last_avail_idx)
    - return vq->num;
    -
    - /* Only get avail ring entries after they have been
    - * exposed by guest.
    - */
    - smp_rmb();
    - }
    -
    - /* Grab the next descriptor number they're advertising, and increment
    - * the index we've seen. */
    - if (unlikely(vhost_get_avail_head(vq, &ring_head, last_avail_idx))) {
    - vq_err(vq, "Failed to read head: idx %d address %p\n",
    - last_avail_idx,
    - &vq->avail->ring[last_avail_idx % vq->num]);
    - return -EFAULT;
    - }
    -
    - head = vhost16_to_cpu(vq, ring_head);
    -
    - /* If their number is silly, that's an error. */
    - if (unlikely(head >= vq->num)) {
    - vq_err(vq, "Guest says index %u > %u is available",
    - head, vq->num);
    - return -EINVAL;
    - }
    -
    - /* When we start there are none of either input nor output. */
    - *out_num = *in_num = 0;
    - if (unlikely(log))
    - *log_num = 0;
    -
    - i = head;
    - do {
    - unsigned iov_count = *in_num + *out_num;
    - if (unlikely(i >= vq->num)) {
    - vq_err(vq, "Desc index is %u > %u, head = %u",
    - i, vq->num, head);
    - return -EINVAL;
    - }
    - if (unlikely(++found > vq->num)) {
    - vq_err(vq, "Loop detected: last one at %u "
    - "vq size %u head %u\n",
    - i, vq->num, head);
    - return -EINVAL;
    - }
    - ret = vhost_get_desc(vq, &desc, i);
    - if (unlikely(ret)) {
    - vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
    - i, vq->desc + i);
    - return -EFAULT;
    - }
    - if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT)) {
    - ret = get_indirect(vq, iov, iov_size,
    - out_num, in_num,
    - log, log_num, &desc);
    - if (unlikely(ret < 0)) {
    - if (ret != -EAGAIN)
    - vq_err(vq, "Failure detected "
    - "in indirect descriptor at idx %d\n", i);
    - return ret;
    - }
    - continue;
    - }
    -
    - if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE))
    - access = VHOST_ACCESS_WO;
    - else
    - access = VHOST_ACCESS_RO;
    - ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr),
    - vhost32_to_cpu(vq, desc.len), iov + iov_count,
    - iov_size - iov_count, access);
    - if (unlikely(ret < 0)) {
    - if (ret != -EAGAIN)
    - vq_err(vq, "Translation failure %d descriptor idx %d\n",
    - ret, i);
    - return ret;
    - }
    - if (access == VHOST_ACCESS_WO) {
    - /* If this is an input descriptor,
    - * increment that count. */
    - *in_num += ret;
    - if (unlikely(log && ret)) {
    - log[*log_num].addr = vhost64_to_cpu(vq, desc.addr);
    - log[*log_num].len = vhost32_to_cpu(vq, desc.len);
    - ++*log_num;
    - }
    - } else {
    - /* If it's an output descriptor, they're all supposed
    - * to come before any input descriptors. */
    - if (unlikely(*in_num)) {
    - vq_err(vq, "Descriptor has out after in: "
    - "idx %d\n", i);
    - return -EINVAL;
    - }
    - *out_num += ret;
    - }
    - } while ((i = next_desc(vq, &desc)) != -1);
    -
    - /* On success, increment avail index. */
    - vq->last_avail_idx++;
    -
    - /* Assume notifications from guest are disabled at this point,
    - * if they aren't we would need to update avail_event index. */
    - BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
    - return head;
    -}
    -EXPORT_SYMBOL_GPL(vhost_get_vq_desc);
    -
    static struct vhost_desc *peek_split_desc(struct vhost_virtqueue *vq)
    {
    BUG_ON(!vq->ndescs);
    @@ -2538,7 +2291,7 @@ static int fetch_descs(struct vhost_virtqueue *vq)
    * This function returns the descriptor number found, or vq->num (which is
    * never a valid descriptor number) if none was found. A negative code is
    * returned on error. */
    -int vhost_get_vq_desc_batch(struct vhost_virtqueue *vq,
    +int vhost_get_vq_desc(struct vhost_virtqueue *vq,
    struct iovec iov[], unsigned int iov_size,
    unsigned int *out_num, unsigned int *in_num,
    struct vhost_log *log, unsigned int *log_num)
    @@ -2613,7 +2366,7 @@ int vhost_get_vq_desc_batch(struct vhost_virtqueue *vq,

    return ret;
    }
    -EXPORT_SYMBOL_GPL(vhost_get_vq_desc_batch);
    +EXPORT_SYMBOL_GPL(vhost_get_vq_desc);

    /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
    void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
    diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
    index 87089d51490d..8a7b4191bc48 100644
    --- a/drivers/vhost/vhost.h
    +++ b/drivers/vhost/vhost.h
    @@ -189,10 +189,6 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
    bool vhost_vq_access_ok(struct vhost_virtqueue *vq);
    bool vhost_log_access_ok(struct vhost_dev *);

    -int vhost_get_vq_desc_batch(struct vhost_virtqueue *,
    - struct iovec iov[], unsigned int iov_count,
    - unsigned int *out_num, unsigned int *in_num,
    - struct vhost_log *log, unsigned int *log_num);
    int vhost_get_vq_desc(struct vhost_virtqueue *,
    struct iovec iov[], unsigned int iov_count,
    unsigned int *out_num, unsigned int *in_num,
    --
    MST
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      Last update: 2020-06-07 16:14    [W:4.574 / U:0.108 seconds]
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