diff mbox

[dpdk-dev,v6] vhost: support virtqueue interrupt/notification suppression

Message ID 1514310190-140916-1-git-send-email-junjie.j.chen@intel.com (mailing list archive)
State Superseded, archived
Delegated to: Yuanhan Liu
Headers show

Checks

Context Check Description
ci/checkpatch success coding style OK
ci/Intel-compilation success Compilation OK

Commit Message

junjie.j.chen@intel.com Dec. 26, 2017, 5:43 p.m. UTC
The driver can suppress interrupt when VIRTIO_F_EVENT_IDX feature bit is
negotiated. The driver set vring flags to 0, and MAY use used_event in
available ring to advise device interrupt util reach an index specified
by used_event. The device ignore the lower bit of vring flags, and send
an interrupt when index reach used_event.

The device can suppress notification in a manner analogous to the ways
driver suppress interrupt. The device manipulates flags or avail_event in
the used ring in the same way the driver manipulates flags or used_event in
available ring.

This patch is to enable this feature in vhost.

Signed-off-by: Junjie Chen <junjie.j.chen@intel.com>

v6: 
Use volatile qualifier to access avail event idx.

v5:
Remove updating avail event index in backend.

v2-v4:
Use definition of VIRTIO_F_EVENT_IDX from kernel.

---
 lib/librte_vhost/vhost.h      |  3 +++
 lib/librte_vhost/virtio_net.c | 46 +++++++++++++++++++++++++++++--------------
 2 files changed, 34 insertions(+), 15 deletions(-)

Comments

Wang, Xiao W Jan. 5, 2018, 5:25 a.m. UTC | #1
Hi,

> -----Original Message-----
> From: Chen, Junjie J
> Sent: Wednesday, December 27, 2017 1:43 AM
> To: Wang, Xiao W <xiao.w.wang@intel.com>; yliu@fridaylinux.org;
> maxime.coquelin@redhat.com; Bie, Tiwei <tiwei.bie@intel.com>
> Cc: dev@dpdk.org; Chen, Junjie J <junjie.j.chen@intel.com>
> Subject: [PATCH v6] vhost: support virtqueue interrupt/notification
> suppression
> 
> The driver can suppress interrupt when VIRTIO_F_EVENT_IDX feature bit is
> negotiated. The driver set vring flags to 0, and MAY use used_event in
> available ring to advise device interrupt util reach an index specified
> by used_event. The device ignore the lower bit of vring flags, and send
> an interrupt when index reach used_event.
> 
> The device can suppress notification in a manner analogous to the ways
> driver suppress interrupt. The device manipulates flags or avail_event in
> the used ring in the same way the driver manipulates flags or used_event in
> available ring.
> 
> This patch is to enable this feature in vhost.
> 
> Signed-off-by: Junjie Chen <junjie.j.chen@intel.com>
> 
> v6:
> Use volatile qualifier to access avail event idx.
> 
> v5:
> Remove updating avail event index in backend.
> 
> v2-v4:
> Use definition of VIRTIO_F_EVENT_IDX from kernel.
> 
> ---
>  lib/librte_vhost/vhost.h      |  3 +++
>  lib/librte_vhost/virtio_net.c | 46 +++++++++++++++++++++++++++++-------------
> -
>  2 files changed, 34 insertions(+), 15 deletions(-)
> 
> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
> index 1cc81c1..fc41c20 100644
> --- a/lib/librte_vhost/vhost.h
> +++ b/lib/librte_vhost/vhost.h
> @@ -103,6 +103,8 @@ struct vhost_virtqueue {
> 
>  	uint16_t		last_avail_idx;
>  	uint16_t		last_used_idx;
> +	/* Last used index we notify to front end. */
> +	uint16_t		signalled_used;
>  #define VIRTIO_INVALID_EVENTFD		(-1)
>  #define VIRTIO_UNINITIALIZED_EVENTFD	(-2)
> 
> @@ -211,6 +213,7 @@ struct vhost_msg {
>  				(1ULL << VIRTIO_NET_F_GUEST_TSO4) | \
>  				(1ULL << VIRTIO_NET_F_GUEST_TSO6) | \
>  				(1ULL << VIRTIO_RING_F_INDIRECT_DESC) | \
> +				(1ULL << VIRTIO_RING_F_EVENT_IDX) | \
>  				(1ULL << VIRTIO_NET_F_MTU) | \
>  				(1ULL << VIRTIO_F_IOMMU_PLATFORM))
> 
> diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
> index 6fee16e..f5777fc 100644
> --- a/lib/librte_vhost/virtio_net.c
> +++ b/lib/librte_vhost/virtio_net.c
> @@ -52,6 +52,34 @@
> 
>  #define MAX_BATCH_LEN 256
> 
> +#define vhost_used_event(vr) \
> +	(*(volatile uint16_t*)&(vr)->avail->ring[(vr)->size])
> +
> +static __rte_always_inline void
> +vhost_notify(struct virtio_net *dev,  struct vhost_virtqueue *vq)
> +{
> +	/* Don't notify guest if we don't reach index specified by guest. */
> +	if (dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX)) {
> +		uint16_t old = vq->signalled_used;
> +		uint16_t new = vq->last_used_idx;
> +
> +		LOG_DEBUG(VHOST_DATA, "%s: used_event_idx=%d, old=%d,
> new=%d\n",
> +			__func__,
> +			vhost_used_event(vq),
> +			old, new);
> +		if (vring_need_event(vhost_used_event(vq), new, old)
> +			&& (vq->callfd >= 0)) {
> +			vq->signalled_used = vq->last_used_idx;
> +			eventfd_write(vq->callfd, (eventfd_t) 1);
> +		}
> +	} else {
> +		/* Kick the guest if necessary. */
> +		if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
> +			&& (vq->callfd >= 0))
> +			eventfd_write(vq->callfd, (eventfd_t)1);
> +	}
> +}
> +
>  static bool
>  is_valid_virt_queue_idx(uint32_t idx, int is_tx, uint32_t nr_vring)
>  {
> @@ -410,11 +438,7 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t
> queue_id,
> 
>  	/* flush used->idx update before we read avail->flags. */
>  	rte_mb();
> -
> -	/* Kick the guest if necessary. */
> -	if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
> -			&& (vq->callfd >= 0))
> -		eventfd_write(vq->callfd, (eventfd_t)1);
> +	vhost_notify(dev, vq);
>  out:
>  	if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM))
>  		vhost_user_iotlb_rd_unlock(vq);
> @@ -704,11 +728,7 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t
> queue_id,
> 
>  		/* flush used->idx update before we read avail->flags. */
>  		rte_mb();
> -
> -		/* Kick the guest if necessary. */
> -		if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
> -				&& (vq->callfd >= 0))
> -			eventfd_write(vq->callfd, (eventfd_t)1);
> +		vhost_notify(dev, vq);
>  	}
> 
>  out:
> @@ -1106,11 +1126,7 @@ update_used_idx(struct virtio_net *dev, struct
> vhost_virtqueue *vq,
>  	vq->used->idx += count;
>  	vhost_log_used_vring(dev, vq, offsetof(struct vring_used, idx),
>  			sizeof(vq->used->idx));
> -
> -	/* Kick guest if required. */
> -	if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
> -			&& (vq->callfd >= 0))
> -		eventfd_write(vq->callfd, (eventfd_t)1);
> +	vhost_notify(dev, vq);
>  }
> 
>  static __rte_always_inline struct zcopy_mbuf *
> --
> 2.0.1

Reviewed-by: Xiao Wang <xiao.w.wang@intel.com>
Yuanhan Liu Jan. 8, 2018, 2:06 p.m. UTC | #2
On Tue, Dec 26, 2017 at 12:43:10PM -0500, Junjie Chen wrote:
> The driver can suppress interrupt when VIRTIO_F_EVENT_IDX feature bit is
> negotiated. The driver set vring flags to 0, and MAY use used_event in
> available ring to advise device interrupt util reach an index specified
> by used_event. The device ignore the lower bit of vring flags, and send
> an interrupt when index reach used_event.
> 
> The device can suppress notification in a manner analogous to the ways
> driver suppress interrupt. The device manipulates flags or avail_event in
> the used ring in the same way the driver manipulates flags or used_event in
> available ring.
> 
> This patch is to enable this feature in vhost.
> 
> Signed-off-by: Junjie Chen <junjie.j.chen@intel.com>

You need put "---" before the change log. Otherwise, it will be tracked in
the commit log.

> +#define vhost_used_event(vr) \
> +	(*(volatile uint16_t*)&(vr)->avail->ring[(vr)->size])
> +
> +static __rte_always_inline void
> +vhost_notify(struct virtio_net *dev,  struct vhost_virtqueue *vq)
> +{
> +	/* Don't notify guest if we don't reach index specified by guest. */
> +	if (dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX)) {
> +		uint16_t old = vq->signalled_used;
> +		uint16_t new = vq->last_used_idx;
> +
> +		LOG_DEBUG(VHOST_DATA, "%s: used_event_idx=%d, old=%d, new=%d\n",
> +			__func__,
> +			vhost_used_event(vq),
> +			old, new);
> +		if (vring_need_event(vhost_used_event(vq), new, old)

It's a bit weird that you use one from the standard linux header file
(vring_need_event), while you define you own one (vhost_used_event).
Note that the system header file also has "vring_used_event()" defined.

Besides that, I have few more comments (and some requirements):

- It'd be much better if there is a Tested-by tag. Expeclitly,
  I'm asking a test with Linux kernel virtio-net driver in guest.

- I also hope you could have done a build test on some old distributions.
  AFAIK, the two macros (vring_need_event and vring_used_event) come
  from kernel 3.0 (or above). Any kernel older than that would fail
  the build.

- I'd be great if you could make a new one based on top of my latest
  tree: I have just applied a patchset that should conflict with this
  one.

	--yliu
junjie.j.chen@intel.com Jan. 9, 2018, 2:12 a.m. UTC | #3
Hi

> -----Original Message-----
> From: Yuanhan Liu [mailto:yliu@fridaylinux.org]
> Sent: Monday, January 8, 2018 10:07 PM
> To: Chen, Junjie J <junjie.j.chen@intel.com>
> Cc: Wang, Xiao W <xiao.w.wang@intel.com>; maxime.coquelin@redhat.com;
> Bie, Tiwei <tiwei.bie@intel.com>; dev@dpdk.org; Yao, Lei A
> <lei.a.yao@intel.com>
> Subject: Re: [PATCH v6] vhost: support virtqueue interrupt/notification
> suppression
> 
> On Tue, Dec 26, 2017 at 12:43:10PM -0500, Junjie Chen wrote:
> > The driver can suppress interrupt when VIRTIO_F_EVENT_IDX feature bit
> > is negotiated. The driver set vring flags to 0, and MAY use used_event
> > in available ring to advise device interrupt util reach an index
> > specified by used_event. The device ignore the lower bit of vring
> > flags, and send an interrupt when index reach used_event.
> >
> > The device can suppress notification in a manner analogous to the ways
> > driver suppress interrupt. The device manipulates flags or avail_event
> > in the used ring in the same way the driver manipulates flags or
> > used_event in available ring.
> >
> > This patch is to enable this feature in vhost.
> >
> > Signed-off-by: Junjie Chen <junjie.j.chen@intel.com>
> 
> You need put "---" before the change log. Otherwise, it will be tracked in the
> commit log.

Will update this.
> 
> > +#define vhost_used_event(vr) \
> > +	(*(volatile uint16_t*)&(vr)->avail->ring[(vr)->size])
> > +
> > +static __rte_always_inline void
> > +vhost_notify(struct virtio_net *dev,  struct vhost_virtqueue *vq) {
> > +	/* Don't notify guest if we don't reach index specified by guest. */
> > +	if (dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX)) {
> > +		uint16_t old = vq->signalled_used;
> > +		uint16_t new = vq->last_used_idx;
> > +
> > +		LOG_DEBUG(VHOST_DATA, "%s: used_event_idx=%d, old=%d,
> new=%d\n",
> > +			__func__,
> > +			vhost_used_event(vq),
> > +			old, new);
> > +		if (vring_need_event(vhost_used_event(vq), new, old)
> 
> It's a bit weird that you use one from the standard linux header file
> (vring_need_event), while you define you own one (vhost_used_event).
> Note that the system header file also has "vring_used_event()" defined.
The vring_used_event is defined and used for virtio in kernel, kernel defines a vhost_used_event in vhost.c for vhost, so I just use a separated macro for vhost end.

I'd like to define both vhost_need_event and vhost_used_event in vhost.h to remove potential build issue in old linux distribution and also to keep consistent. Is that OK for you?

> 
> Besides that, I have few more comments (and some requirements):
> 
> - It'd be much better if there is a Tested-by tag. Expeclitly,
>   I'm asking a test with Linux kernel virtio-net driver in guest.
Sure.
> 
> - I also hope you could have done a build test on some old distributions.
>   AFAIK, the two macros (vring_need_event and vring_used_event) come
>   from kernel 3.0 (or above). Any kernel older than that would fail
>   the build.
> 
> - I'd be great if you could make a new one based on top of my latest
>   tree: I have just applied a patchset that should conflict with this
>   one.

Sure, will do this.
> 
> 	--yliu
Yuanhan Liu Jan. 9, 2018, 2:29 a.m. UTC | #4
On Tue, Jan 09, 2018 at 02:12:02AM +0000, Chen, Junjie J wrote:
> > > +		if (vring_need_event(vhost_used_event(vq), new, old)
> > 
> > It's a bit weird that you use one from the standard linux header file
> > (vring_need_event), while you define you own one (vhost_used_event).
> > Note that the system header file also has "vring_used_event()" defined.
> The vring_used_event is defined and used for virtio in kernel, kernel defines a vhost_used_event in vhost.c for vhost, so I just use a separated macro for vhost end.
> 
> I'd like to define both vhost_need_event and vhost_used_event in vhost.h to remove potential build issue in old linux distribution and also to keep consistent. Is that OK for you?

Yes.

	--yliu
diff mbox

Patch

diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index 1cc81c1..fc41c20 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -103,6 +103,8 @@  struct vhost_virtqueue {
 
 	uint16_t		last_avail_idx;
 	uint16_t		last_used_idx;
+	/* Last used index we notify to front end. */
+	uint16_t		signalled_used;
 #define VIRTIO_INVALID_EVENTFD		(-1)
 #define VIRTIO_UNINITIALIZED_EVENTFD	(-2)
 
@@ -211,6 +213,7 @@  struct vhost_msg {
 				(1ULL << VIRTIO_NET_F_GUEST_TSO4) | \
 				(1ULL << VIRTIO_NET_F_GUEST_TSO6) | \
 				(1ULL << VIRTIO_RING_F_INDIRECT_DESC) | \
+				(1ULL << VIRTIO_RING_F_EVENT_IDX) | \
 				(1ULL << VIRTIO_NET_F_MTU) | \
 				(1ULL << VIRTIO_F_IOMMU_PLATFORM))
 
diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 6fee16e..f5777fc 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -52,6 +52,34 @@ 
 
 #define MAX_BATCH_LEN 256
 
+#define vhost_used_event(vr) \
+	(*(volatile uint16_t*)&(vr)->avail->ring[(vr)->size])
+
+static __rte_always_inline void
+vhost_notify(struct virtio_net *dev,  struct vhost_virtqueue *vq)
+{
+	/* Don't notify guest if we don't reach index specified by guest. */
+	if (dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX)) {
+		uint16_t old = vq->signalled_used;
+		uint16_t new = vq->last_used_idx;
+
+		LOG_DEBUG(VHOST_DATA, "%s: used_event_idx=%d, old=%d, new=%d\n",
+			__func__,
+			vhost_used_event(vq),
+			old, new);
+		if (vring_need_event(vhost_used_event(vq), new, old)
+			&& (vq->callfd >= 0)) {
+			vq->signalled_used = vq->last_used_idx;
+			eventfd_write(vq->callfd, (eventfd_t) 1);
+		}
+	} else {
+		/* Kick the guest if necessary. */
+		if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
+			&& (vq->callfd >= 0))
+			eventfd_write(vq->callfd, (eventfd_t)1);
+	}
+}
+
 static bool
 is_valid_virt_queue_idx(uint32_t idx, int is_tx, uint32_t nr_vring)
 {
@@ -410,11 +438,7 @@  virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 
 	/* flush used->idx update before we read avail->flags. */
 	rte_mb();
-
-	/* Kick the guest if necessary. */
-	if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
-			&& (vq->callfd >= 0))
-		eventfd_write(vq->callfd, (eventfd_t)1);
+	vhost_notify(dev, vq);
 out:
 	if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM))
 		vhost_user_iotlb_rd_unlock(vq);
@@ -704,11 +728,7 @@  virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
 
 		/* flush used->idx update before we read avail->flags. */
 		rte_mb();
-
-		/* Kick the guest if necessary. */
-		if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
-				&& (vq->callfd >= 0))
-			eventfd_write(vq->callfd, (eventfd_t)1);
+		vhost_notify(dev, vq);
 	}
 
 out:
@@ -1106,11 +1126,7 @@  update_used_idx(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	vq->used->idx += count;
 	vhost_log_used_vring(dev, vq, offsetof(struct vring_used, idx),
 			sizeof(vq->used->idx));
-
-	/* Kick guest if required. */
-	if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
-			&& (vq->callfd >= 0))
-		eventfd_write(vq->callfd, (eventfd_t)1);
+	vhost_notify(dev, vq);
 }
 
 static __rte_always_inline struct zcopy_mbuf *