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Date: Tue, 14 Sep 2010 18:01:02 +0200
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Jason Wang <jasowang@...hat.com>
Cc: virtualization@...ts.osdl.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH] vhost: max s/g to match qemu
On Tue, Sep 14, 2010 at 11:53:05PM +0800, Jason Wang wrote:
> Qemu supports up to UIO_MAXIOV s/g so we have to match that because guest
> drivers may rely on this.
>
> Allocate indirect and log arrays dynamically to avoid using too much contigious
> memory and make the length of hdr array to match the header length since each
> iovec entry has a least one byte.
>
> Test with copying large files w/ and w/o migration in both linux and windows
> guests.
>
> Signed-off-by: Jason Wang <jasowang@...hat.com>
Looks good, I'll queue this up for 2.6.37.
Thanks!
> ---
> drivers/vhost/net.c | 2 +-
> drivers/vhost/vhost.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++-
> drivers/vhost/vhost.h | 18 ++++++++----------
> 3 files changed, 57 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 29e850a..e828ef1 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -243,7 +243,7 @@ static int get_rx_bufs(struct vhost_virtqueue *vq,
> int r, nlogs = 0;
>
> while (datalen > 0) {
> - if (unlikely(headcount >= VHOST_NET_MAX_SG)) {
> + if (unlikely(headcount >= UIO_MAXIOV)) {
> r = -ENOBUFS;
> goto err;
> }
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index c579dcc..a45270e 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -212,6 +212,45 @@ static int vhost_worker(void *data)
> }
> }
>
> +/* Helper to allocate iovec buffers for all vqs. */
> +static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
> +{
> + int i;
> + for (i = 0; i < dev->nvqs; ++i) {
> + dev->vqs[i].indirect = kmalloc(sizeof *dev->vqs[i].indirect *
> + UIO_MAXIOV, GFP_KERNEL);
> + dev->vqs[i].log = kmalloc(sizeof *dev->vqs[i].log * UIO_MAXIOV,
> + GFP_KERNEL);
> + dev->vqs[i].heads = kmalloc(sizeof *dev->vqs[i].heads *
> + UIO_MAXIOV, GFP_KERNEL);
> +
> + if (!dev->vqs[i].indirect || !dev->vqs[i].log ||
> + !dev->vqs[i].heads)
> + goto err_nomem;
> + }
> + return 0;
> +err_nomem:
> + for (; i >= 0; --i) {
> + kfree(dev->vqs[i].indirect);
> + kfree(dev->vqs[i].log);
> + kfree(dev->vqs[i].heads);
We probably want to assign NULL values here, same as below.
I have fixed this up in my tree.
> + }
> + return -ENOMEM;
> +}
> +
> +static void vhost_dev_free_iovecs(struct vhost_dev *dev)
> +{
> + int i;
> + for (i = 0; i < dev->nvqs; ++i) {
> + kfree(dev->vqs[i].indirect);
> + dev->vqs[i].indirect = NULL;
> + kfree(dev->vqs[i].log);
> + dev->vqs[i].log = NULL;
> + kfree(dev->vqs[i].heads);
> + dev->vqs[i].heads = NULL;
> + }
> +}
> +
> long vhost_dev_init(struct vhost_dev *dev,
> struct vhost_virtqueue *vqs, int nvqs)
> {
> @@ -229,6 +268,9 @@ long vhost_dev_init(struct vhost_dev *dev,
> dev->worker = NULL;
>
> for (i = 0; i < dev->nvqs; ++i) {
> + dev->vqs[i].log = NULL;
> + dev->vqs[i].indirect = NULL;
> + dev->vqs[i].heads = NULL;
> dev->vqs[i].dev = dev;
> mutex_init(&dev->vqs[i].mutex);
> vhost_vq_reset(dev, dev->vqs + i);
> @@ -295,6 +337,10 @@ static long vhost_dev_set_owner(struct vhost_dev *dev)
> if (err)
> goto err_cgroup;
>
> + err = vhost_dev_alloc_iovecs(dev);
> + if (err)
> + goto err_cgroup;
> +
> return 0;
> err_cgroup:
> kthread_stop(worker);
> @@ -345,6 +391,7 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
> fput(dev->vqs[i].call);
> vhost_vq_reset(dev, dev->vqs + i);
> }
> + vhost_dev_free_iovecs(dev);
> if (dev->log_ctx)
> eventfd_ctx_put(dev->log_ctx);
> dev->log_ctx = NULL;
> @@ -946,7 +993,7 @@ static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
> }
>
> ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
> - ARRAY_SIZE(vq->indirect));
> + UIO_MAXIOV);
> if (unlikely(ret < 0)) {
> vq_err(vq, "Translation failure %d in indirect.\n", ret);
> return ret;
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index afd7729..edc8929 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -15,11 +15,6 @@
>
> struct vhost_device;
>
> -enum {
> - /* Enough place for all fragments, head, and virtio net header. */
> - VHOST_NET_MAX_SG = MAX_SKB_FRAGS + 2,
> -};
> -
> struct vhost_work;
> typedef void (*vhost_work_fn_t)(struct vhost_work *work);
>
> @@ -93,12 +88,15 @@ struct vhost_virtqueue {
> bool log_used;
> u64 log_addr;
>
> - struct iovec indirect[VHOST_NET_MAX_SG];
> - struct iovec iov[VHOST_NET_MAX_SG];
> - struct iovec hdr[VHOST_NET_MAX_SG];
> + struct iovec iov[UIO_MAXIOV];
> + /* hdr is used to store the virtio header.
> + * Since each iovec has >= 1 byte length, we never need more than
> + * header length entries to store the header. */
> + struct iovec hdr[sizeof(struct virtio_net_hdr_mrg_rxbuf)];
> + struct iovec *indirect;
> size_t vhost_hlen;
> size_t sock_hlen;
> - struct vring_used_elem heads[VHOST_NET_MAX_SG];
> + struct vring_used_elem *heads;
> /* We use a kind of RCU to access private pointer.
> * All readers access it from worker, which makes it possible to
> * flush the vhost_work instead of synchronize_rcu. Therefore readers do
> @@ -109,7 +107,7 @@ struct vhost_virtqueue {
> void *private_data;
> /* Log write descriptors */
> void __user *log_base;
> - struct vhost_log log[VHOST_NET_MAX_SG];
> + struct vhost_log *log;
> };
>
> struct vhost_dev {
--
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