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[Qemu-devel] [PATCH 1/2] libvhost-user: support resuming vq->last_avail_idx based on used_idx

Marc-André Lureau posted 2 patches 8 years, 2 months ago
There is a newer version of this series
[Qemu-devel] [PATCH 1/2] libvhost-user: support resuming vq->last_avail_idx based on used_idx
Posted by Marc-André Lureau 8 years, 2 months ago 
This is the same workaround as commit 523b018dde3b765, which was lost
with libvhost-user transition in commit e10e798c85c2331.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 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);
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
Re: [Qemu-devel] [PATCH 1/2] libvhost-user: support resuming vq->last_avail_idx based on used_idx
Posted by Michael S. Tsirkin 8 years, 2 months ago 
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 <marcandre.lureau@redhat.com>
> ---
>  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
Re: [Qemu-devel] [PATCH 1/2] libvhost-user: support resuming vq->last_avail_idx based on used_idx
Posted by Marc-André Lureau 8 years, 2 months ago 
Hi

On Tue, Aug 29, 2017 at 5:01 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> 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 <marcandre.lureau@redhat.com>
>> ---
>>  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.
>
That's what the comment say already :)

Which name do you suggest? vu_queue_is_processed_in_order? Does that
imply it should always resume?

>
>> 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
>



-- 
Marc-André Lureau
Re: [Qemu-devel] [PATCH 1/2] libvhost-user: support resuming vq->last_avail_idx based on used_idx
Posted by Michael S. Tsirkin 8 years, 2 months ago 
On Tue, Aug 29, 2017 at 05:04:34PM +0200, Marc-André Lureau wrote:
> Hi
> 
> On Tue, Aug 29, 2017 at 5:01 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > 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 <marcandre.lureau@redhat.com>
> >> ---
> >>  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.
> >
> That's what the comment say already :)
> 
> Which name do you suggest? vu_queue_is_processed_in_order?

Something like this.

> Does that
> imply it should always resume?

Not sure I understand the question.

> >
> >> 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
> >
> 
> 
> 
> -- 
> Marc-André Lureau
Re: [Qemu-devel] [PATCH 1/2] libvhost-user: support resuming vq->last_avail_idx based on used_idx
Posted by Marc-André Lureau 8 years, 2 months ago 
Hi

On Tue, Aug 29, 2017 at 5:09 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> On Tue, Aug 29, 2017 at 05:04:34PM +0200, Marc-André Lureau wrote:
>> Hi
>>
>> On Tue, Aug 29, 2017 at 5:01 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
>> > 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 <marcandre.lureau@redhat.com>
>> >> ---
>> >>  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.
>> >
>> That's what the comment say already :)
>>
>> Which name do you suggest? vu_queue_is_processed_in_order?
>
> Something like this.
>
>> Does that
>> imply it should always resume?
>
> Not sure I understand the question.

If a "queue_is_processed_in_order", does that imply libvhost-user
should always resume it based on used_idx? I think it does, but the
correlation is less obvious than explicitly saying "resume_to_used".


-- 
Marc-André Lureau
Re: [Qemu-devel] [PATCH 1/2] libvhost-user: support resuming vq->last_avail_idx based on used_idx
Posted by Michael S. Tsirkin 8 years, 2 months ago 
On Tue, Aug 29, 2017 at 05:18:11PM +0200, Marc-André Lureau wrote:
> Hi
> 
> On Tue, Aug 29, 2017 at 5:09 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> > On Tue, Aug 29, 2017 at 05:04:34PM +0200, Marc-André Lureau wrote:
> >> Hi
> >>
> >> On Tue, Aug 29, 2017 at 5:01 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> >> > 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 <marcandre.lureau@redhat.com>
> >> >> ---
> >> >>  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.
> >> >
> >> That's what the comment say already :)
> >>
> >> Which name do you suggest? vu_queue_is_processed_in_order?
> >
> > Something like this.
> >
> >> Does that
> >> imply it should always resume?
> >
> > Not sure I understand the question.
> 
> If a "queue_is_processed_in_order", does that imply libvhost-user
> should always resume it based on used_idx? I think it does, but the
> correlation is less obvious than explicitly saying "resume_to_used".

Just add a comment then. You do not want low level details
like used index in all backends.


> 
> -- 
> Marc-André Lureau

Patchew 2.1-devel-b67e4c2

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