[PATCH 1/4] kvm tools: Support VIRTIO_RING_F_EVENT_IDX

[PATCH 1/4] kvm tools: Support VIRTIO_RING_F_EVENT_IDX

[Sasha Levin]

Support the event index feature in the virtio spec.

The results are less notifications between the guest and host, and in
result faster operation of the virt queues.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
 tools/kvm/include/kvm/virtio.h |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/tools/kvm/include/kvm/virtio.h b/tools/kvm/include/kvm/virtio.h
index c6c380d..cd24285 100644
--- a/tools/kvm/include/kvm/virtio.h
+++ b/tools/kvm/include/kvm/virtio.h
@@ -38,6 +38,8 @@ static inline bool virt_queue__available(struct virt_queue *vq)
 {
 	if (!vq->vring.avail)
 		return 0;
+
+	vring_avail_event(&vq->vring) = vq->last_avail_idx;
 	return vq->vring.avail->idx !=  vq->last_avail_idx;
 }
 
@@ -51,6 +53,11 @@ static inline void *guest_pfn_to_host(struct kvm *kvm, u32 pfn)
 	return guest_flat_to_host(kvm, (unsigned long)pfn << VIRTIO_PCI_QUEUE_ADDR_SHIFT);
 }
 
+static inline int virtio_queue__should_signal(struct virt_queue *vq)
+{
+	return vring_used_event(&vq->vring) <= vq->vring.used->idx;
+}
+
 struct vring_used_elem *virt_queue__set_used_elem(struct virt_queue *queue, u32 head, u32 len);
 
 u16 virt_queue__get_iov(struct virt_queue *queue, struct iovec iov[], u16 *out, u16 *in, struct kvm *kvm);
-- 
1.7.8.rc1

[PATCH 2/4] kvm tools: Add '--no-dhcp' to disable kernel DHCP

[Sasha Levin]

This new option disables the kernel DHCP which runs when starting
a custom rootfs.

This is useful when we want to start a rootfs but are using a network
other than the usermode IP proxy (a network which doesn't provide DHCP).

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
 tools/kvm/builtin-run.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/tools/kvm/builtin-run.c b/tools/kvm/builtin-run.c
index 3b00bf0..43cf2c4 100644
--- a/tools/kvm/builtin-run.c
+++ b/tools/kvm/builtin-run.c
@@ -91,6 +91,7 @@ static bool balloon;
 static bool using_rootfs;
 static bool custom_rootfs;
 static bool no_net;
+static bool no_dhcp;
 extern bool ioport_debug;
 extern int  active_console;
 extern int  debug_iodelay;
@@ -432,6 +433,7 @@ static const struct option options[] = {
 	OPT_CALLBACK_DEFAULT('n', "network", NULL, "network params",
 		     "Create a new guest NIC",
 		     netdev_parser, NULL),
+	OPT_BOOLEAN('\0', "no-dhcp", &no_dhcp, "Disable kernel DHCP in rootfs mode"),
 
 	OPT_GROUP("BIOS options:"),
 	OPT_INTEGER('\0', "vidmode", &vidmode,
@@ -861,8 +863,11 @@ int kvm_cmd_run(int argc, const char **argv, const char *prefix)
 
 	if (using_rootfs) {
 		strcat(real_cmdline, " root=/dev/root rw rootflags=rw,trans=virtio,version=9p2000.L rootfstype=9p");
-		if (custom_rootfs)
-			strcat(real_cmdline, " init=/virt/init ip=dhcp");
+		if (custom_rootfs) {
+			strcat(real_cmdline, " init=/virt/init");
+			if (!no_dhcp)
+				strcat(real_cmdline, "  ip=dhcp");
+		}
 	} else if (!strstr(real_cmdline, "root=")) {
 		strlcat(real_cmdline, " root=/dev/vda rw ", sizeof(real_cmdline));
 	}
-- 
1.7.8.rc1

[PATCH 3/4] kvm tools: Support event idx in virtio-net

[Sasha Levin]

Support event idx both when using vhost and when using simple TAP mode.

I did simple TCP stream performance test with vhost, and it showed another 9%
increase over regular vhost mode.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
 tools/kvm/virtio/net.c |   12 ++++++++----
 1 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/tools/kvm/virtio/net.c b/tools/kvm/virtio/net.c
index 58ca4ed..118517f 100644
--- a/tools/kvm/virtio/net.c
+++ b/tools/kvm/virtio/net.c
@@ -102,7 +102,9 @@ static void *virtio_net_rx_thread(void *p)
 			virt_queue__set_used_elem(vq, head, len);
 
 			/* We should interrupt guest right now, otherwise latency is huge. */
-			ndev->vtrans.trans_ops->signal_vq(kvm, &ndev->vtrans, VIRTIO_NET_RX_QUEUE);
+			if (virtio_queue__should_signal(&ndev->vqs[VIRTIO_NET_RX_QUEUE]))
+				ndev->vtrans.trans_ops->signal_vq(kvm, &ndev->vtrans,
+								VIRTIO_NET_RX_QUEUE);
 		}
 
 	}
@@ -140,7 +142,8 @@ static void *virtio_net_tx_thread(void *p)
 			virt_queue__set_used_elem(vq, head, len);
 		}
 
-		ndev->vtrans.trans_ops->signal_vq(kvm, &ndev->vtrans, VIRTIO_NET_TX_QUEUE);
+		if (virtio_queue__should_signal(&ndev->vqs[VIRTIO_NET_TX_QUEUE]))
+			ndev->vtrans.trans_ops->signal_vq(kvm, &ndev->vtrans, VIRTIO_NET_TX_QUEUE);
 	}
 
 	pthread_exit(NULL);
@@ -314,7 +317,8 @@ static u32 get_host_features(struct kvm *kvm, void *dev)
 		| 1UL << VIRTIO_NET_F_HOST_TSO6
 		| 1UL << VIRTIO_NET_F_GUEST_UFO
 		| 1UL << VIRTIO_NET_F_GUEST_TSO4
-		| 1UL << VIRTIO_NET_F_GUEST_TSO6;
+		| 1UL << VIRTIO_NET_F_GUEST_TSO6
+		| 1UL << VIRTIO_RING_F_EVENT_IDX;
 }
 
 static void set_guest_features(struct kvm *kvm, void *dev, u32 features)
@@ -453,7 +457,7 @@ static struct virtio_ops net_dev_virtio_ops = (struct virtio_ops) {
 
 static void virtio_net__vhost_init(struct kvm *kvm, struct net_dev *ndev)
 {
-	u64 features = 0;
+	u64 features = 1UL << VIRTIO_RING_F_EVENT_IDX;
 	struct vhost_memory *mem;
 	int r;
 
-- 
1.7.8.rc1

[PATCH 4/4] kvm tool: Add event idx support to virtio-blk

[Sasha Levin]

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
 tools/kvm/virtio/blk.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/tools/kvm/virtio/blk.c b/tools/kvm/virtio/blk.c
index ed4e099..9495f28 100644
--- a/tools/kvm/virtio/blk.c
+++ b/tools/kvm/virtio/blk.c
@@ -93,7 +93,8 @@ void virtio_blk_complete(void *param, long len)
 	virt_queue__set_used_elem(req->vq, req->head, len);
 	mutex_unlock(&bdev->mutex);
 
-	bdev->vtrans.trans_ops->signal_vq(req->kvm, &bdev->vtrans, queueid);
+	if (virtio_queue__should_signal(&bdev->vqs[queueid]))
+		bdev->vtrans.trans_ops->signal_vq(req->kvm, &bdev->vtrans, queueid);
 
 	virtio_blk_req_push(req->bdev, req);
 }
@@ -170,7 +171,9 @@ static u8 get_config(struct kvm *kvm, void *dev, u32 offset)
 
 static u32 get_host_features(struct kvm *kvm, void *dev)
 {
-	return 1UL << VIRTIO_BLK_F_SEG_MAX | 1UL << VIRTIO_BLK_F_FLUSH;
+	return	1UL << VIRTIO_BLK_F_SEG_MAX
+		| 1UL << VIRTIO_BLK_F_FLUSH
+		| 1UL << VIRTIO_RING_F_EVENT_IDX;
 }
 
 static void set_guest_features(struct kvm *kvm, void *dev, u32 features)
-- 
1.7.8.rc1

Re: [PATCH 1/4] kvm tools: Support VIRTIO_RING_F_EVENT_IDX

[Pekka Enberg]

On Thu, Nov 17, 2011 at 3:04 PM, Sasha Levin <levinsasha928@gmail.com> wrote:
> Support the event index feature in the virtio spec.
>
> The results are less notifications between the guest and host, and in
> result faster operation of the virt queues.
>
> Signed-off-by: Sasha Levin <levinsasha928@gmail.com>

What's this patch doing? There's no mention of VIRTIO_RING_F_EVENT_IDX
in the diff...

> ---
>  tools/kvm/include/kvm/virtio.h |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)
>
> diff --git a/tools/kvm/include/kvm/virtio.h b/tools/kvm/include/kvm/virtio.h
> index c6c380d..cd24285 100644
> --- a/tools/kvm/include/kvm/virtio.h
> +++ b/tools/kvm/include/kvm/virtio.h
> @@ -38,6 +38,8 @@ static inline bool virt_queue__available(struct virt_queue *vq)
>  {
>        if (!vq->vring.avail)
>                return 0;
> +
> +       vring_avail_event(&vq->vring) = vq->last_avail_idx;
>        return vq->vring.avail->idx !=  vq->last_avail_idx;
>  }
>
> @@ -51,6 +53,11 @@ static inline void *guest_pfn_to_host(struct kvm *kvm, u32 pfn)
>        return guest_flat_to_host(kvm, (unsigned long)pfn << VIRTIO_PCI_QUEUE_ADDR_SHIFT);
>  }
>
> +static inline int virtio_queue__should_signal(struct virt_queue *vq)
> +{
> +       return vring_used_event(&vq->vring) <= vq->vring.used->idx;
> +}
> +
>  struct vring_used_elem *virt_queue__set_used_elem(struct virt_queue *queue, u32 head, u32 len);
>
>  u16 virt_queue__get_iov(struct virt_queue *queue, struct iovec iov[], u16 *out, u16 *in, struct kvm *kvm);
> --
> 1.7.8.rc1
>
> --
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>

Re: [PATCH 1/4] kvm tools: Support VIRTIO_RING_F_EVENT_IDX

[Sasha Levin]

On Thu, 2011-11-17 at 15:24 +0200, Pekka Enberg wrote:
> On Thu, Nov 17, 2011 at 3:04 PM, Sasha Levin <levinsasha928@gmail.com> wrote:
> > Support the event index feature in the virtio spec.
> >
> > The results are less notifications between the guest and host, and in
> > result faster operation of the virt queues.
> >
> > Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
> 
> What's this patch doing? There's no mention of VIRTIO_RING_F_EVENT_IDX
> in the diff...

It allows enabling the VIRTIO_RING_F_EVENT_IDX feature in various
virtio-* devices by updating the avail event idx and providing a
function to allow the devices to query the vq and decide if they need to
signal the VQ or not.

-- 

Sasha.

Re: [PATCH 1/4] kvm tools: Support VIRTIO_RING_F_EVENT_IDX

[Pekka Enberg]

> On Thu, 2011-11-17 at 15:24 +0200, Pekka Enberg wrote:
>> On Thu, Nov 17, 2011 at 3:04 PM, Sasha Levin <levinsasha928@gmail.com> wrote:
>> > Support the event index feature in the virtio spec.
>> >
>> > The results are less notifications between the guest and host, and in
>> > result faster operation of the virt queues.
>> >
>> > Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
>>
>> What's this patch doing? There's no mention of VIRTIO_RING_F_EVENT_IDX
>> in the diff...

On Thu, Nov 17, 2011 at 3:36 PM, Sasha Levin <levinsasha928@gmail.com> wrote:
> It allows enabling the VIRTIO_RING_F_EVENT_IDX feature in various
> virtio-* devices by updating the avail event idx and providing a
> function to allow the devices to query the vq and decide if they need to
> signal the VQ or not.

Right. The changelog is extremely confusing as is the ordering in the
patch series. You usually write something like "in preparation for
enabling XYZ support, add helper functions" and include the
conversions immediately after the helpers.

I'll fix the issues myself later today when I have the change to merge
patches. That is, unless you beat me to it and send a v2 of the
series.

                        Pekka