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Re: [Qemu-devel] [PATCH 1/2] libvhost-user: support resuming vq->last_av
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH 1/2] libvhost-user: support resuming vq->last_avail_idx based on used_idx |
Date: |
Tue, 29 Aug 2017 18:01:30 +0300 |
On Tue, Aug 29, 2017 at 04:48:04PM +0200, Marc-André Lureau wrote:
> This is the same workaround as commit 523b018dde3b765, which was lost
> with libvhost-user transition in commit e10e798c85c2331.
>
> Signed-off-by: Marc-André Lureau <address@hidden>
> ---
> contrib/libvhost-user/libvhost-user.h | 5 +++++
> contrib/libvhost-user/libvhost-user.c | 13 +++++++++++++
> 2 files changed, 18 insertions(+)
>
> diff --git a/contrib/libvhost-user/libvhost-user.h
> b/contrib/libvhost-user/libvhost-user.h
> index 53ef222c0b..aca71717c1 100644
> --- a/contrib/libvhost-user/libvhost-user.h
> +++ b/contrib/libvhost-user/libvhost-user.h
> @@ -132,6 +132,7 @@ typedef void (*vu_set_features_cb) (VuDev *dev, uint64_t
> features);
> typedef int (*vu_process_msg_cb) (VuDev *dev, VhostUserMsg *vmsg,
> int *do_reply);
> typedef void (*vu_queue_set_started_cb) (VuDev *dev, int qidx, bool started);
> +typedef bool (*vu_queue_resume_to_used_cb) (VuDev *dev, int qidx);
>
> typedef struct VuDevIface {
> /* called by VHOST_USER_GET_FEATURES to get the features bitmask */
> @@ -148,6 +149,10 @@ typedef struct VuDevIface {
> vu_process_msg_cb process_msg;
> /* tells when queues can be processed */
> vu_queue_set_started_cb queue_set_started;
> + /* If the queue must be resumed to vring.used->idx. */
> + /* This can help to support resuming on unmanaged exit/crash when
> + * the slave/driver processes elements in order. */
> + vu_queue_resume_to_used_cb queue_resume_to_used;
> } VuDevIface;
>
> typedef void (*vu_queue_handler_cb) (VuDev *dev, int qidx);
Let's consider: this is only safe if queue is processed in order.
So I think that would be a better name for the field.
> diff --git a/contrib/libvhost-user/libvhost-user.c
> b/contrib/libvhost-user/libvhost-user.c
> index 35fa0c5e56..36439caed6 100644
> --- a/contrib/libvhost-user/libvhost-user.c
> +++ b/contrib/libvhost-user/libvhost-user.c
> @@ -521,6 +521,19 @@ vu_set_vring_addr_exec(VuDev *dev, VhostUserMsg *vmsg)
>
> vq->used_idx = vq->vring.used->idx;
>
> + if (vq->last_avail_idx != vq->used_idx) {
> + bool resume = dev->iface->queue_resume_to_used &&
> + dev->iface->queue_resume_to_used(dev, index);
> +
> + DPRINT("Last avail index != used index: %u != %u%s\n",
> + vq->last_avail_idx, vq->used_idx,
> + resume ? ", resuming" : "");
> +
> + if (resume) {
> + vq->shadow_avail_idx = vq->last_avail_idx = vq->used_idx;
> + }
> + }
> +
> return false;
> }
>
> --
> 2.14.1.146.gd35faa819
[Qemu-devel] [PATCH 2/2] vhost-user-bridge: fix resume regression (since 2.9), Marc-André Lureau, 2017/08/29
Re: [Qemu-devel] [PATCH 0/2] vhost-user-bridge reconnect regression, Michael S. Tsirkin, 2017/08/29