* [PATCH v4] virtio_ring: interrupt disable flag updated to vq even with event_triggered is set
@ 2023-03-29 10:23 Albert Huang
2023-03-29 11:45 ` Xuan Zhuo
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Albert Huang @ 2023-03-29 10:23 UTC (permalink / raw)
To: Jason Wang, Michael S . Tsirkin
Cc: huangjie.albert, virtualization, linux-kernel
From: "huangjie.albert" <huangjie.albert@bytedance.com>
in virtio_net, if we disable the napi_tx, when we triger a tx interrupt,
the vq->event_triggered will be set to true. It will no longer be set to
false. Unless we explicitly call virtqueue_enable_cb_delayed or
virtqueue_enable_cb_prepare.
If we disable the napi_tx, it will only be called when the tx ring
buffer is relatively small.
Because event_triggered is true. Therefore, VRING_AVAIL_F_NO_INTERRUPT or
VRING_PACKED_EVENT_FLAG_DISABLE will not be set. So we update
vring_used_event(&vq->split.vring) or vq->packed.vring.driver->off_wrap
every time we call virtqueue_get_buf_ctx.This bring more interruptions.
To summarize:
1) event_triggered was set to true in vring_interrupt()
2) after this nothing will happen for virtqueue_disable_cb() so
VRING_AVAIL_F_NO_INTERRUPT is not set in avail_flags_shadow
3) virtqueue_get_buf_ctx_split() will still think the cb is enabled
then it tries to publish new event
To fix:
update VRING_AVAIL_F_NO_INTERRUPT or VRING_PACKED_EVENT_FLAG_DISABLE to vq
when we call virtqueue_disable_cb even the event_triggered is set to true.
Tested with iperf:
iperf3 tcp stream:
vm1 -----------------> vm2
vm2 just receives tcp data stream from vm1, and sends the ack to vm1,
there are many tx interrupts in vm2.
but without event_triggered there are just a few tx interrupts.
v2->v3:
-update the interrupt disable flag even with the event_triggered is set,
-instead of checking whether event_triggered is set in
-virtqueue_get_buf_ctx_{packed/split}, will cause the drivers which have
-not called virtqueue_{enable/disable}_cb to miss notifications.
v3->v4:
-remove change for
-"if (vq->packed.event_flags_shadow != VRING_PACKED_EVENT_FLAG_DISABLE)"
-in virtqueue_disable_cb_packed
Fixes: 8d622d21d248 ("virtio: fix up virtio_disable_cb")
Signed-off-by: huangjie.albert <huangjie.albert@bytedance.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
drivers/virtio/virtio_ring.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index cbeeea1b0439..ec7ab8e04846 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -931,6 +931,14 @@ static void virtqueue_disable_cb_split(struct virtqueue *_vq)
if (!(vq->split.avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
vq->split.avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
+
+ /*
+ * If device triggered an event already it won't trigger one again:
+ * no need to disable.
+ */
+ if (vq->event_triggered)
+ return;
+
if (vq->event)
/* TODO: this is a hack. Figure out a cleaner value to write. */
vring_used_event(&vq->split.vring) = 0x0;
@@ -1761,6 +1769,14 @@ static void virtqueue_disable_cb_packed(struct virtqueue *_vq)
if (vq->packed.event_flags_shadow != VRING_PACKED_EVENT_FLAG_DISABLE) {
vq->packed.event_flags_shadow = VRING_PACKED_EVENT_FLAG_DISABLE;
+
+ /*
+ * If device triggered an event already it won't trigger one again:
+ * no need to disable.
+ */
+ if (vq->event_triggered)
+ return;
+
vq->packed.vring.driver->flags =
cpu_to_le16(vq->packed.event_flags_shadow);
}
@@ -2462,12 +2478,6 @@ void virtqueue_disable_cb(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
- /* If device triggered an event already it won't trigger one again:
- * no need to disable.
- */
- if (vq->event_triggered)
- return;
-
if (vq->packed_ring)
virtqueue_disable_cb_packed(_vq);
else
--
2.20.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v4] virtio_ring: interrupt disable flag updated to vq even with event_triggered is set
2023-03-29 10:23 [PATCH v4] virtio_ring: interrupt disable flag updated to vq even with event_triggered is set Albert Huang
@ 2023-03-29 11:45 ` Xuan Zhuo
2023-03-29 16:34 ` Michael S. Tsirkin
2023-03-29 16:36 ` Michael S. Tsirkin
2023-03-29 16:40 ` Michael S. Tsirkin
2 siblings, 1 reply; 6+ messages in thread
From: Xuan Zhuo @ 2023-03-29 11:45 UTC (permalink / raw)
To: Albert Huang
Cc: huangjie.albert, virtualization, linux-kernel, Jason Wang,
Michael S . Tsirkin
On Wed, 29 Mar 2023 18:23:00 +0800, Albert Huang <huangjie.albert@bytedance.com> wrote:
> From: "huangjie.albert" <huangjie.albert@bytedance.com>
>
> in virtio_net, if we disable the napi_tx, when we triger a tx interrupt,
> the vq->event_triggered will be set to true. It will no longer be set to
> false. Unless we explicitly call virtqueue_enable_cb_delayed or
> virtqueue_enable_cb_prepare.
>
> If we disable the napi_tx, it will only be called when the tx ring
> buffer is relatively small.
>
> Because event_triggered is true. Therefore, VRING_AVAIL_F_NO_INTERRUPT or
> VRING_PACKED_EVENT_FLAG_DISABLE will not be set. So we update
> vring_used_event(&vq->split.vring) or vq->packed.vring.driver->off_wrap
> every time we call virtqueue_get_buf_ctx.This bring more interruptions.
>
> To summarize:
> 1) event_triggered was set to true in vring_interrupt()
> 2) after this nothing will happen for virtqueue_disable_cb() so
> VRING_AVAIL_F_NO_INTERRUPT is not set in avail_flags_shadow
> 3) virtqueue_get_buf_ctx_split() will still think the cb is enabled
> then it tries to publish new event
>
> To fix:
> update VRING_AVAIL_F_NO_INTERRUPT or VRING_PACKED_EVENT_FLAG_DISABLE to vq
> when we call virtqueue_disable_cb even the event_triggered is set to true.
>
> Tested with iperf:
> iperf3 tcp stream:
> vm1 -----------------> vm2
> vm2 just receives tcp data stream from vm1, and sends the ack to vm1,
> there are many tx interrupts in vm2.
> but without event_triggered there are just a few tx interrupts.
>
> v2->v3:
> -update the interrupt disable flag even with the event_triggered is set,
> -instead of checking whether event_triggered is set in
> -virtqueue_get_buf_ctx_{packed/split}, will cause the drivers which have
> -not called virtqueue_{enable/disable}_cb to miss notifications.
>
> v3->v4:
> -remove change for
> -"if (vq->packed.event_flags_shadow != VRING_PACKED_EVENT_FLAG_DISABLE)"
> -in virtqueue_disable_cb_packed
>
> Fixes: 8d622d21d248 ("virtio: fix up virtio_disable_cb")
Hi Michael,
I want to know what the purpose of this patch("virtio: fix up virtio_disable_cb")
is. I re-review this patch. I didn't understand what the purpose of this
patches. Does it reduce one write to vring_used_event(&vq->split.vring) ?
Thanks.
> Signed-off-by: huangjie.albert <huangjie.albert@bytedance.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
> drivers/virtio/virtio_ring.c | 22 ++++++++++++++++------
> 1 file changed, 16 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index cbeeea1b0439..ec7ab8e04846 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -931,6 +931,14 @@ static void virtqueue_disable_cb_split(struct virtqueue *_vq)
>
> if (!(vq->split.avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
> vq->split.avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
> +
> + /*
> + * If device triggered an event already it won't trigger one again:
> + * no need to disable.
> + */
> + if (vq->event_triggered)
> + return;
> +
> if (vq->event)
> /* TODO: this is a hack. Figure out a cleaner value to write. */
> vring_used_event(&vq->split.vring) = 0x0;
> @@ -1761,6 +1769,14 @@ static void virtqueue_disable_cb_packed(struct virtqueue *_vq)
>
> if (vq->packed.event_flags_shadow != VRING_PACKED_EVENT_FLAG_DISABLE) {
> vq->packed.event_flags_shadow = VRING_PACKED_EVENT_FLAG_DISABLE;
> +
> + /*
> + * If device triggered an event already it won't trigger one again:
> + * no need to disable.
> + */
> + if (vq->event_triggered)
> + return;
> +
> vq->packed.vring.driver->flags =
> cpu_to_le16(vq->packed.event_flags_shadow);
> }
> @@ -2462,12 +2478,6 @@ void virtqueue_disable_cb(struct virtqueue *_vq)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> - /* If device triggered an event already it won't trigger one again:
> - * no need to disable.
> - */
> - if (vq->event_triggered)
> - return;
> -
> if (vq->packed_ring)
> virtqueue_disable_cb_packed(_vq);
> else
> --
> 2.20.1
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v4] virtio_ring: interrupt disable flag updated to vq even with event_triggered is set
2023-03-29 11:45 ` Xuan Zhuo
@ 2023-03-29 16:34 ` Michael S. Tsirkin
0 siblings, 0 replies; 6+ messages in thread
From: Michael S. Tsirkin @ 2023-03-29 16:34 UTC (permalink / raw)
To: Xuan Zhuo; +Cc: Albert Huang, virtualization, linux-kernel, Jason Wang
On Wed, Mar 29, 2023 at 07:45:01PM +0800, Xuan Zhuo wrote:
> On Wed, 29 Mar 2023 18:23:00 +0800, Albert Huang <huangjie.albert@bytedance.com> wrote:
> > From: "huangjie.albert" <huangjie.albert@bytedance.com>
> >
> > in virtio_net, if we disable the napi_tx, when we triger a tx interrupt,
> > the vq->event_triggered will be set to true. It will no longer be set to
> > false. Unless we explicitly call virtqueue_enable_cb_delayed or
> > virtqueue_enable_cb_prepare.
> >
> > If we disable the napi_tx, it will only be called when the tx ring
> > buffer is relatively small.
> >
> > Because event_triggered is true. Therefore, VRING_AVAIL_F_NO_INTERRUPT or
> > VRING_PACKED_EVENT_FLAG_DISABLE will not be set. So we update
> > vring_used_event(&vq->split.vring) or vq->packed.vring.driver->off_wrap
> > every time we call virtqueue_get_buf_ctx.This bring more interruptions.
> >
> > To summarize:
> > 1) event_triggered was set to true in vring_interrupt()
> > 2) after this nothing will happen for virtqueue_disable_cb() so
> > VRING_AVAIL_F_NO_INTERRUPT is not set in avail_flags_shadow
> > 3) virtqueue_get_buf_ctx_split() will still think the cb is enabled
> > then it tries to publish new event
> >
> > To fix:
> > update VRING_AVAIL_F_NO_INTERRUPT or VRING_PACKED_EVENT_FLAG_DISABLE to vq
> > when we call virtqueue_disable_cb even the event_triggered is set to true.
> >
> > Tested with iperf:
> > iperf3 tcp stream:
> > vm1 -----------------> vm2
> > vm2 just receives tcp data stream from vm1, and sends the ack to vm1,
> > there are many tx interrupts in vm2.
> > but without event_triggered there are just a few tx interrupts.
> >
> > v2->v3:
> > -update the interrupt disable flag even with the event_triggered is set,
> > -instead of checking whether event_triggered is set in
> > -virtqueue_get_buf_ctx_{packed/split}, will cause the drivers which have
> > -not called virtqueue_{enable/disable}_cb to miss notifications.
> >
> > v3->v4:
> > -remove change for
> > -"if (vq->packed.event_flags_shadow != VRING_PACKED_EVENT_FLAG_DISABLE)"
> > -in virtqueue_disable_cb_packed
> >
> > Fixes: 8d622d21d248 ("virtio: fix up virtio_disable_cb")
>
> Hi Michael,
>
> I want to know what the purpose of this patch("virtio: fix up virtio_disable_cb")
> is. I re-review this patch. I didn't understand what the purpose of this
> patches. Does it reduce one write to vring_used_event(&vq->split.vring) ?
>
> Thanks.
Are you asking why I applied 8d622d21d248 ("virtio: fix up
virtio_disable_cb")?
It was a prerequisite to fixing interrupt storms we saw in the field previously.
See Message-ID: <20210413011508-mutt-send-email-mst@kernel.org>
for the bug report and Message-ID: <20210413054733.36363-1-mst@redhat.com>
for the original patchset fixing it.
>
> > Signed-off-by: huangjie.albert <huangjie.albert@bytedance.com>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > Signed-off-by: Jason Wang <jasowang@redhat.com>
> > ---
> > drivers/virtio/virtio_ring.c | 22 ++++++++++++++++------
> > 1 file changed, 16 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > index cbeeea1b0439..ec7ab8e04846 100644
> > --- a/drivers/virtio/virtio_ring.c
> > +++ b/drivers/virtio/virtio_ring.c
> > @@ -931,6 +931,14 @@ static void virtqueue_disable_cb_split(struct virtqueue *_vq)
> >
> > if (!(vq->split.avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
> > vq->split.avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
> > +
> > + /*
> > + * If device triggered an event already it won't trigger one again:
> > + * no need to disable.
> > + */
> > + if (vq->event_triggered)
> > + return;
> > +
> > if (vq->event)
> > /* TODO: this is a hack. Figure out a cleaner value to write. */
> > vring_used_event(&vq->split.vring) = 0x0;
> > @@ -1761,6 +1769,14 @@ static void virtqueue_disable_cb_packed(struct virtqueue *_vq)
> >
> > if (vq->packed.event_flags_shadow != VRING_PACKED_EVENT_FLAG_DISABLE) {
> > vq->packed.event_flags_shadow = VRING_PACKED_EVENT_FLAG_DISABLE;
> > +
> > + /*
> > + * If device triggered an event already it won't trigger one again:
> > + * no need to disable.
> > + */
> > + if (vq->event_triggered)
> > + return;
> > +
> > vq->packed.vring.driver->flags =
> > cpu_to_le16(vq->packed.event_flags_shadow);
> > }
> > @@ -2462,12 +2478,6 @@ void virtqueue_disable_cb(struct virtqueue *_vq)
> > {
> > struct vring_virtqueue *vq = to_vvq(_vq);
> >
> > - /* If device triggered an event already it won't trigger one again:
> > - * no need to disable.
> > - */
> > - if (vq->event_triggered)
> > - return;
> > -
> > if (vq->packed_ring)
> > virtqueue_disable_cb_packed(_vq);
> > else
> > --
> > 2.20.1
> >
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v4] virtio_ring: interrupt disable flag updated to vq even with event_triggered is set
2023-03-29 10:23 [PATCH v4] virtio_ring: interrupt disable flag updated to vq even with event_triggered is set Albert Huang
2023-03-29 11:45 ` Xuan Zhuo
@ 2023-03-29 16:36 ` Michael S. Tsirkin
2023-03-29 16:40 ` Michael S. Tsirkin
2 siblings, 0 replies; 6+ messages in thread
From: Michael S. Tsirkin @ 2023-03-29 16:36 UTC (permalink / raw)
To: Albert Huang; +Cc: Jason Wang, virtualization, linux-kernel
On Wed, Mar 29, 2023 at 06:23:00PM +0800, Albert Huang wrote:
> From: "huangjie.albert" <huangjie.albert@bytedance.com>
>
> in virtio_net, if we disable the napi_tx, when we triger a tx interrupt,
> the vq->event_triggered will be set to true. It will no longer be set to
> false. Unless we explicitly call virtqueue_enable_cb_delayed or
> virtqueue_enable_cb_prepare.
>
> If we disable the napi_tx, it will only be called when the tx ring
> buffer is relatively small.
>
> Because event_triggered is true. Therefore, VRING_AVAIL_F_NO_INTERRUPT or
> VRING_PACKED_EVENT_FLAG_DISABLE will not be set. So we update
> vring_used_event(&vq->split.vring) or vq->packed.vring.driver->off_wrap
> every time we call virtqueue_get_buf_ctx.This bring more interruptions.
>
> To summarize:
> 1) event_triggered was set to true in vring_interrupt()
> 2) after this nothing will happen for virtqueue_disable_cb() so
> VRING_AVAIL_F_NO_INTERRUPT is not set in avail_flags_shadow
> 3) virtqueue_get_buf_ctx_split() will still think the cb is enabled
> then it tries to publish new event
>
> To fix:
> update VRING_AVAIL_F_NO_INTERRUPT or VRING_PACKED_EVENT_FLAG_DISABLE to vq
> when we call virtqueue_disable_cb even the event_triggered is set to true.
>
> Tested with iperf:
> iperf3 tcp stream:
> vm1 -----------------> vm2
> vm2 just receives tcp data stream from vm1, and sends the ack to vm1,
> there are many tx interrupts in vm2.
> but without event_triggered there are just a few tx interrupts.
>
> v2->v3:
> -update the interrupt disable flag even with the event_triggered is set,
> -instead of checking whether event_triggered is set in
> -virtqueue_get_buf_ctx_{packed/split}, will cause the drivers which have
> -not called virtqueue_{enable/disable}_cb to miss notifications.
>
> v3->v4:
> -remove change for
> -"if (vq->packed.event_flags_shadow != VRING_PACKED_EVENT_FLAG_DISABLE)"
> -in virtqueue_disable_cb_packed
>
> Fixes: 8d622d21d248 ("virtio: fix up virtio_disable_cb")
> Signed-off-by: huangjie.albert <huangjie.albert@bytedance.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
Patch is ok so I rewrote the commit log and applied.
Please do not add signed-off-by tags by others -
read up what this tag means.
I also rewrote your Signed-off-by to have your name
formatted same as in email - hope that is ok.
> ---
> drivers/virtio/virtio_ring.c | 22 ++++++++++++++++------
> 1 file changed, 16 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index cbeeea1b0439..ec7ab8e04846 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -931,6 +931,14 @@ static void virtqueue_disable_cb_split(struct virtqueue *_vq)
>
> if (!(vq->split.avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
> vq->split.avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
> +
> + /*
> + * If device triggered an event already it won't trigger one again:
> + * no need to disable.
> + */
> + if (vq->event_triggered)
> + return;
> +
> if (vq->event)
> /* TODO: this is a hack. Figure out a cleaner value to write. */
> vring_used_event(&vq->split.vring) = 0x0;
> @@ -1761,6 +1769,14 @@ static void virtqueue_disable_cb_packed(struct virtqueue *_vq)
>
> if (vq->packed.event_flags_shadow != VRING_PACKED_EVENT_FLAG_DISABLE) {
> vq->packed.event_flags_shadow = VRING_PACKED_EVENT_FLAG_DISABLE;
> +
> + /*
> + * If device triggered an event already it won't trigger one again:
> + * no need to disable.
> + */
> + if (vq->event_triggered)
> + return;
> +
> vq->packed.vring.driver->flags =
> cpu_to_le16(vq->packed.event_flags_shadow);
> }
> @@ -2462,12 +2478,6 @@ void virtqueue_disable_cb(struct virtqueue *_vq)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> - /* If device triggered an event already it won't trigger one again:
> - * no need to disable.
> - */
> - if (vq->event_triggered)
> - return;
> -
> if (vq->packed_ring)
> virtqueue_disable_cb_packed(_vq);
> else
> --
> 2.20.1
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v4] virtio_ring: interrupt disable flag updated to vq even with event_triggered is set
2023-03-29 10:23 [PATCH v4] virtio_ring: interrupt disable flag updated to vq even with event_triggered is set Albert Huang
2023-03-29 11:45 ` Xuan Zhuo
2023-03-29 16:36 ` Michael S. Tsirkin
@ 2023-03-29 16:40 ` Michael S. Tsirkin
2023-03-30 2:15 ` [External] " 黄杰
2 siblings, 1 reply; 6+ messages in thread
From: Michael S. Tsirkin @ 2023-03-29 16:40 UTC (permalink / raw)
To: Albert Huang; +Cc: Jason Wang, virtualization, linux-kernel
On Wed, Mar 29, 2023 at 06:23:00PM +0800, Albert Huang wrote:
> From: "huangjie.albert" <huangjie.albert@bytedance.com>
>
> in virtio_net, if we disable the napi_tx, when we triger a tx interrupt,
> the vq->event_triggered will be set to true. It will no longer be set to
> false. Unless we explicitly call virtqueue_enable_cb_delayed or
> virtqueue_enable_cb_prepare.
>
> If we disable the napi_tx, it will only be called when the tx ring
> buffer is relatively small.
>
> Because event_triggered is true. Therefore, VRING_AVAIL_F_NO_INTERRUPT or
> VRING_PACKED_EVENT_FLAG_DISABLE will not be set. So we update
> vring_used_event(&vq->split.vring) or vq->packed.vring.driver->off_wrap
> every time we call virtqueue_get_buf_ctx.This bring more interruptions.
>
> To summarize:
> 1) event_triggered was set to true in vring_interrupt()
> 2) after this nothing will happen for virtqueue_disable_cb() so
> VRING_AVAIL_F_NO_INTERRUPT is not set in avail_flags_shadow
> 3) virtqueue_get_buf_ctx_split() will still think the cb is enabled
> then it tries to publish new event
>
> To fix:
> update VRING_AVAIL_F_NO_INTERRUPT or VRING_PACKED_EVENT_FLAG_DISABLE to vq
> when we call virtqueue_disable_cb even the event_triggered is set to true.
>
> Tested with iperf:
> iperf3 tcp stream:
> vm1 -----------------> vm2
> vm2 just receives tcp data stream from vm1, and sends the ack to vm1,
> there are many tx interrupts in vm2.
> but without event_triggered there are just a few tx interrupts.
>
> v2->v3:
> -update the interrupt disable flag even with the event_triggered is set,
> -instead of checking whether event_triggered is set in
> -virtqueue_get_buf_ctx_{packed/split}, will cause the drivers which have
> -not called virtqueue_{enable/disable}_cb to miss notifications.
>
> v3->v4:
> -remove change for
> -"if (vq->packed.event_flags_shadow != VRING_PACKED_EVENT_FLAG_DISABLE)"
> -in virtqueue_disable_cb_packed
>
> Fixes: 8d622d21d248 ("virtio: fix up virtio_disable_cb")
> Signed-off-by: huangjie.albert <huangjie.albert@bytedance.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
Can you confirm you tested 9p and it still works fine?
> ---
> drivers/virtio/virtio_ring.c | 22 ++++++++++++++++------
> 1 file changed, 16 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index cbeeea1b0439..ec7ab8e04846 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -931,6 +931,14 @@ static void virtqueue_disable_cb_split(struct virtqueue *_vq)
>
> if (!(vq->split.avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
> vq->split.avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
> +
> + /*
> + * If device triggered an event already it won't trigger one again:
> + * no need to disable.
> + */
> + if (vq->event_triggered)
> + return;
> +
> if (vq->event)
> /* TODO: this is a hack. Figure out a cleaner value to write. */
> vring_used_event(&vq->split.vring) = 0x0;
> @@ -1761,6 +1769,14 @@ static void virtqueue_disable_cb_packed(struct virtqueue *_vq)
>
> if (vq->packed.event_flags_shadow != VRING_PACKED_EVENT_FLAG_DISABLE) {
> vq->packed.event_flags_shadow = VRING_PACKED_EVENT_FLAG_DISABLE;
> +
> + /*
> + * If device triggered an event already it won't trigger one again:
> + * no need to disable.
> + */
> + if (vq->event_triggered)
> + return;
> +
> vq->packed.vring.driver->flags =
> cpu_to_le16(vq->packed.event_flags_shadow);
> }
> @@ -2462,12 +2478,6 @@ void virtqueue_disable_cb(struct virtqueue *_vq)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> - /* If device triggered an event already it won't trigger one again:
> - * no need to disable.
> - */
> - if (vq->event_triggered)
> - return;
> -
> if (vq->packed_ring)
> virtqueue_disable_cb_packed(_vq);
> else
> --
> 2.20.1
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [External] Re: [PATCH v4] virtio_ring: interrupt disable flag updated to vq even with event_triggered is set
2023-03-29 16:40 ` Michael S. Tsirkin
@ 2023-03-30 2:15 ` 黄杰
0 siblings, 0 replies; 6+ messages in thread
From: 黄杰 @ 2023-03-30 2:15 UTC (permalink / raw)
To: Michael S. Tsirkin; +Cc: Jason Wang, virtualization, linux-kernel
Michael S. Tsirkin <mst@redhat.com> 于2023年3月30日周四 00:40写道:
>
> On Wed, Mar 29, 2023 at 06:23:00PM +0800, Albert Huang wrote:
> > From: "huangjie.albert" <huangjie.albert@bytedance.com>
> >
> > in virtio_net, if we disable the napi_tx, when we triger a tx interrupt,
> > the vq->event_triggered will be set to true. It will no longer be set to
> > false. Unless we explicitly call virtqueue_enable_cb_delayed or
> > virtqueue_enable_cb_prepare.
> >
> > If we disable the napi_tx, it will only be called when the tx ring
> > buffer is relatively small.
> >
> > Because event_triggered is true. Therefore, VRING_AVAIL_F_NO_INTERRUPT or
> > VRING_PACKED_EVENT_FLAG_DISABLE will not be set. So we update
> > vring_used_event(&vq->split.vring) or vq->packed.vring.driver->off_wrap
> > every time we call virtqueue_get_buf_ctx.This bring more interruptions.
> >
> > To summarize:
> > 1) event_triggered was set to true in vring_interrupt()
> > 2) after this nothing will happen for virtqueue_disable_cb() so
> > VRING_AVAIL_F_NO_INTERRUPT is not set in avail_flags_shadow
> > 3) virtqueue_get_buf_ctx_split() will still think the cb is enabled
> > then it tries to publish new event
> >
> > To fix:
> > update VRING_AVAIL_F_NO_INTERRUPT or VRING_PACKED_EVENT_FLAG_DISABLE to vq
> > when we call virtqueue_disable_cb even the event_triggered is set to true.
> >
> > Tested with iperf:
> > iperf3 tcp stream:
> > vm1 -----------------> vm2
> > vm2 just receives tcp data stream from vm1, and sends the ack to vm1,
> > there are many tx interrupts in vm2.
> > but without event_triggered there are just a few tx interrupts.
> >
> > v2->v3:
> > -update the interrupt disable flag even with the event_triggered is set,
> > -instead of checking whether event_triggered is set in
> > -virtqueue_get_buf_ctx_{packed/split}, will cause the drivers which have
> > -not called virtqueue_{enable/disable}_cb to miss notifications.
> >
> > v3->v4:
> > -remove change for
> > -"if (vq->packed.event_flags_shadow != VRING_PACKED_EVENT_FLAG_DISABLE)"
> > -in virtqueue_disable_cb_packed
> >
> > Fixes: 8d622d21d248 ("virtio: fix up virtio_disable_cb")
> > Signed-off-by: huangjie.albert <huangjie.albert@bytedance.com>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > Signed-off-by: Jason Wang <jasowang@redhat.com>
>
> Can you confirm you tested 9p and it still works fine?
>
Yes, I tested it in my local environment. After applying this patch,
9p works fine.
Thanks.
> > ---
> > drivers/virtio/virtio_ring.c | 22 ++++++++++++++++------
> > 1 file changed, 16 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > index cbeeea1b0439..ec7ab8e04846 100644
> > --- a/drivers/virtio/virtio_ring.c
> > +++ b/drivers/virtio/virtio_ring.c
> > @@ -931,6 +931,14 @@ static void virtqueue_disable_cb_split(struct virtqueue *_vq)
> >
> > if (!(vq->split.avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
> > vq->split.avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
> > +
> > + /*
> > + * If device triggered an event already it won't trigger one again:
> > + * no need to disable.
> > + */
> > + if (vq->event_triggered)
> > + return;
> > +
> > if (vq->event)
> > /* TODO: this is a hack. Figure out a cleaner value to write. */
> > vring_used_event(&vq->split.vring) = 0x0;
> > @@ -1761,6 +1769,14 @@ static void virtqueue_disable_cb_packed(struct virtqueue *_vq)
> >
> > if (vq->packed.event_flags_shadow != VRING_PACKED_EVENT_FLAG_DISABLE) {
> > vq->packed.event_flags_shadow = VRING_PACKED_EVENT_FLAG_DISABLE;
> > +
> > + /*
> > + * If device triggered an event already it won't trigger one again:
> > + * no need to disable.
> > + */
> > + if (vq->event_triggered)
> > + return;
> > +
> > vq->packed.vring.driver->flags =
> > cpu_to_le16(vq->packed.event_flags_shadow);
> > }
> > @@ -2462,12 +2478,6 @@ void virtqueue_disable_cb(struct virtqueue *_vq)
> > {
> > struct vring_virtqueue *vq = to_vvq(_vq);
> >
> > - /* If device triggered an event already it won't trigger one again:
> > - * no need to disable.
> > - */
> > - if (vq->event_triggered)
> > - return;
> > -
> > if (vq->packed_ring)
> > virtqueue_disable_cb_packed(_vq);
> > else
> > --
> > 2.20.1
>
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2023-03-30 2:16 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-03-29 10:23 [PATCH v4] virtio_ring: interrupt disable flag updated to vq even with event_triggered is set Albert Huang
2023-03-29 11:45 ` Xuan Zhuo
2023-03-29 16:34 ` Michael S. Tsirkin
2023-03-29 16:36 ` Michael S. Tsirkin
2023-03-29 16:40 ` Michael S. Tsirkin
2023-03-30 2:15 ` [External] " 黄杰
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