[dpdk-dev] [PATCH 0/4] Vhost: fix mq=on but VIRTIO_NET_F_MQ not negotiated

[dpdk-dev] [PATCH 0/4] Vhost: fix mq=on but VIRTIO_NET_F_MQ not negotiated

[Maxime Coquelin]

Having QEMU started with mq=on but guest driver not negotiating
VIRTIO_NET_F_MQ feature ends up in the vhost device to never
start. Indeed, more queues are created in the vhost backend than
configured.

Guest drivers known to not advertise the VIRTIO_NET_F_MQ feature are
iPXE and OVMF Virtio-net drivers.

Queues are created because before starting the guest, QEMU sends
VHOST_USER_SET_VRING_CALL requests for all queues declared in QEMU
command line. Also, once Virtio features negotiated, QEMU sends
VHOST_USER_SET_VRING_ENABLE requests to disable all but the first
queue pair.

This series fixes this by destroying all but first queue pair in
the backend if VIRTIO_NET_F_MQ isn't negotiated. First patches
makes sure that VHOST_USER_SET_FEATURES request doesn't change
Virtio features while the device is running, which should never
happen as per the Virtio spec. This helps to make sure vitqueues
aren't destroyed while being processed, but also protect from
other illegal features changes (e.g. VIRTIO_NET_F_MRG_RXBUF).

Maxime Coquelin (4):
  vhost: prevent features to be changed while device is running
  vhost: propagate VHOST_USER_SET_FEATURES handling error
  vhost: extract virtqueue cleaning and freeing functions
  vhost: destroy unused virtqueues when multiqueue not negotiated

 lib/librte_vhost/vhost.c      | 22 ++++++++++++----------
 lib/librte_vhost/vhost.h      |  3 +++
 lib/librte_vhost/vhost_user.c | 40 ++++++++++++++++++++++++++++++++++++++--
 3 files changed, 53 insertions(+), 12 deletions(-)

-- 
2.14.3

[dpdk-dev] [PATCH 1/4] vhost: prevent features to be changed while device is running

[Maxime Coquelin]

As section 2.2 of the Virtio spec states about features
negotiation:
"During device initialization, the driver reads this and tells
the device the subset that it accepts. The only way to
renegotiate is to reset the device."

This patch implements a check to prevent illegal features change
while the device is running.

One exception is the VHOST_F_LOG_ALL feature bit, which is enabled
when live-migration is initiated. But this feature is not negotiated
with the Virtio driver, but directly with the Vhost master.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/librte_vhost/vhost_user.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index f4c7ce462..f51055ab2 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -183,7 +183,22 @@ vhost_user_set_features(struct virtio_net *dev, uint64_t features)
 		return -1;
 	}
 
-	if ((dev->flags & VIRTIO_DEV_RUNNING) && dev->features != features) {
+	if (dev->features == features)
+		return 0;
+
+	if (dev->flags & VIRTIO_DEV_RUNNING) {
+		/*
+		 * Error out if master tries to change features while device is
+		 * in running state. The exception being VHOST_F_LOG_ALL, which
+		 * is enabled when the live-migration starts.
+		 */
+		if ((dev->features ^ features) & ~(1ULL >> VHOST_F_LOG_ALL)) {
+			RTE_LOG(ERR, VHOST_CONFIG,
+				"(%d) features changed while device is running.\n",
+				dev->vid);
+			return -1;
+		}
+
 		if (dev->notify_ops->features_changed)
 			dev->notify_ops->features_changed(dev->vid, features);
 	}
-- 
2.14.3

[dpdk-dev] [PATCH 2/4] vhost: propagate VHOST_USER_SET_FEATURES handling error

[Maxime Coquelin]

Not propagating VHOST_USER_SET_FEATURES request handling
error may result in unpredictable behavior, as host and
guests features may no more be synchronized.

This patch fixes this by reporting the error to the upper
layer, which would result in the device being destroyed
and the connection with the master to be closed.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/librte_vhost/vhost_user.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index f51055ab2..7d84af3e2 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -1263,7 +1263,9 @@ vhost_user_msg_handler(int vid, int fd)
 		send_vhost_reply(fd, &msg);
 		break;
 	case VHOST_USER_SET_FEATURES:
-		vhost_user_set_features(dev, msg.payload.u64);
+		ret = vhost_user_set_features(dev, msg.payload.u64);
+		if (ret)
+			return -1;
 		break;
 
 	case VHOST_USER_GET_PROTOCOL_FEATURES:
-- 
2.14.3

[dpdk-dev] [PATCH 3/4] vhost: extract virtqueue cleaning and freeing functions

[Maxime Coquelin]

This patch extracts needed code for vhost_user.c to be able
to clean and free virtqueues unitary.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/librte_vhost/vhost.c | 22 ++++++++++++----------
 lib/librte_vhost/vhost.h |  3 +++
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
index 4f8b73a09..df528a4ea 100644
--- a/lib/librte_vhost/vhost.c
+++ b/lib/librte_vhost/vhost.c
@@ -103,7 +103,7 @@ get_device(int vid)
 	return dev;
 }
 
-static void
+void
 cleanup_vq(struct vhost_virtqueue *vq, int destroy)
 {
 	if ((vq->callfd >= 0) && (destroy != 0))
@@ -127,6 +127,15 @@ cleanup_device(struct virtio_net *dev, int destroy)
 		cleanup_vq(dev->virtqueue[i], destroy);
 }
 
+void
+free_vq(struct vhost_virtqueue *vq)
+{
+	rte_free(vq->shadow_used_ring);
+	rte_free(vq->batch_copy_elems);
+	rte_mempool_free(vq->iotlb_pool);
+	rte_free(vq);
+}
+
 /*
  * Release virtqueues and device memory.
  */
@@ -134,16 +143,9 @@ static void
 free_device(struct virtio_net *dev)
 {
 	uint32_t i;
-	struct vhost_virtqueue *vq;
-
-	for (i = 0; i < dev->nr_vring; i++) {
-		vq = dev->virtqueue[i];
 
-		rte_free(vq->shadow_used_ring);
-		rte_free(vq->batch_copy_elems);
-		rte_mempool_free(vq->iotlb_pool);
-		rte_free(vq);
-	}
+	for (i = 0; i < dev->nr_vring; i++)
+		free_vq(dev->virtqueue[i]);
 
 	rte_free(dev);
 }
diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index 1cc81c17c..9cad1bb3c 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -364,6 +364,9 @@ void cleanup_device(struct virtio_net *dev, int destroy);
 void reset_device(struct virtio_net *dev);
 void vhost_destroy_device(int);
 
+void cleanup_vq(struct vhost_virtqueue *vq, int destroy);
+void free_vq(struct vhost_virtqueue *vq);
+
 int alloc_vring_queue(struct virtio_net *dev, uint32_t vring_idx);
 
 void vhost_set_ifname(int, const char *if_name, unsigned int if_len);
-- 
2.14.3

[dpdk-dev] [PATCH 4/4] vhost: destroy unused virtqueues when multiqueue not negotiated

[Maxime Coquelin]

QEMU sends VHOST_USER_SET_VRING_CALL requests for all queues
declared in QEMU command line before the guest is started.
It has the effect in DPDK vhost-user backend to allocate vrings
for all queues declared by QEMU.

If the first driver being used does not support multiqueue,
the device never changes to VIRTIO_DEV_RUNNING state as only
the first queue pair is initialized. One driver impacted by
this bug is virtio-net's iPXE driver which does not support
VIRTIO_NET_F_MQ feature.

It is safe to destroy unused virtqueues in SET_FEATURES request
handler, as it is ensured the device is not in running state
at this stage, so virtqueues aren't being processed.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/librte_vhost/vhost_user.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index 7d84af3e2..72526e006 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -173,6 +173,7 @@ vhost_user_get_features(struct virtio_net *dev)
 static int
 vhost_user_set_features(struct virtio_net *dev, uint64_t features)
 {
+	int i;
 	uint64_t vhost_features = 0;
 
 	rte_vhost_driver_get_features(dev->ifname, &vhost_features);
@@ -216,6 +217,24 @@ vhost_user_set_features(struct virtio_net *dev, uint64_t features)
 		(dev->features & (1 << VIRTIO_NET_F_MRG_RXBUF)) ? "on" : "off",
 		(dev->features & (1ULL << VIRTIO_F_VERSION_1)) ? "on" : "off");
 
+	if (!(dev->features & (1ULL << VIRTIO_NET_F_MQ))) {
+		/*
+		 * Remove all but first queue pair if MQ hasn't been
+		 * negotiated. This is safe because the device is not
+		 * running at this stage.
+		 */
+		for (i = dev->nr_vring; i > 1; i--) {
+			struct vhost_virtqueue *vq = dev->virtqueue[i];
+
+			if (!vq)
+				continue;
+
+			cleanup_vq(vq, 1);
+			free_vq(vq);
+			dev->nr_vring--;
+		}
+	}
+
 	return 0;
 }
 
-- 
2.14.3

Re: [dpdk-dev] [PATCH 1/4] vhost: prevent features to be changed while device is running

[Ladi Prosek]

On Mon, Dec 4, 2017 at 3:08 PM, Maxime Coquelin
<maxime.coquelin@redhat.com> wrote:
> As section 2.2 of the Virtio spec states about features
> negotiation:
> "During device initialization, the driver reads this and tells
> the device the subset that it accepts. The only way to
> renegotiate is to reset the device."
>
> This patch implements a check to prevent illegal features change
> while the device is running.
>
> One exception is the VHOST_F_LOG_ALL feature bit, which is enabled
> when live-migration is initiated. But this feature is not negotiated
> with the Virtio driver, but directly with the Vhost master.
>
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  lib/librte_vhost/vhost_user.c | 17 ++++++++++++++++-
>  1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
> index f4c7ce462..f51055ab2 100644
> --- a/lib/librte_vhost/vhost_user.c
> +++ b/lib/librte_vhost/vhost_user.c
> @@ -183,7 +183,22 @@ vhost_user_set_features(struct virtio_net *dev, uint64_t features)
>                 return -1;
>         }
>
> -       if ((dev->flags & VIRTIO_DEV_RUNNING) && dev->features != features) {
> +       if (dev->features == features)
> +               return 0;
> +
> +       if (dev->flags & VIRTIO_DEV_RUNNING) {
> +               /*
> +                * Error out if master tries to change features while device is
> +                * in running state. The exception being VHOST_F_LOG_ALL, which
> +                * is enabled when the live-migration starts.
> +                */
> +               if ((dev->features ^ features) & ~(1ULL >> VHOST_F_LOG_ALL)) {

The 1 should be shifted to the left:

  1ULL << VHOST_F_LOG_ALL


> +                       RTE_LOG(ERR, VHOST_CONFIG,
> +                               "(%d) features changed while device is running.\n",
> +                               dev->vid);
> +                       return -1;
> +               }
> +
>                 if (dev->notify_ops->features_changed)
>                         dev->notify_ops->features_changed(dev->vid, features);
>         }
> --
> 2.14.3
>

Re: [dpdk-dev] [PATCH 1/4] vhost: prevent features to be changed while device is running

[Maxime Coquelin]

On 12/04/2017 03:17 PM, Ladi Prosek wrote:
> On Mon, Dec 4, 2017 at 3:08 PM, Maxime Coquelin
> <maxime.coquelin@redhat.com>  wrote:
>> As section 2.2 of the Virtio spec states about features
>> negotiation:
>> "During device initialization, the driver reads this and tells
>> the device the subset that it accepts. The only way to
>> renegotiate is to reset the device."
>>
>> This patch implements a check to prevent illegal features change
>> while the device is running.
>>
>> One exception is the VHOST_F_LOG_ALL feature bit, which is enabled
>> when live-migration is initiated. But this feature is not negotiated
>> with the Virtio driver, but directly with the Vhost master.
>>
>> Signed-off-by: Maxime Coquelin<maxime.coquelin@redhat.com>
>> ---
>>   lib/librte_vhost/vhost_user.c | 17 ++++++++++++++++-
>>   1 file changed, 16 insertions(+), 1 deletion(-)
>>
>> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
>> index f4c7ce462..f51055ab2 100644
>> --- a/lib/librte_vhost/vhost_user.c
>> +++ b/lib/librte_vhost/vhost_user.c
>> @@ -183,7 +183,22 @@ vhost_user_set_features(struct virtio_net *dev, uint64_t features)
>>                  return -1;
>>          }
>>
>> -       if ((dev->flags & VIRTIO_DEV_RUNNING) && dev->features != features) {
>> +       if (dev->features == features)
>> +               return 0;
>> +
>> +       if (dev->flags & VIRTIO_DEV_RUNNING) {
>> +               /*
>> +                * Error out if master tries to change features while device is
>> +                * in running state. The exception being VHOST_F_LOG_ALL, which
>> +                * is enabled when the live-migration starts.
>> +                */
>> +               if ((dev->features ^ features) & ~(1ULL >> VHOST_F_LOG_ALL)) {
> The 1 should be shifted to the left:
> 
>    1ULL << VHOST_F_LOG_ALL

Oh right, of course.

Thanks for spotting this.
Maxime

Re: [dpdk-dev] [PATCH 0/4] Vhost: fix mq=on but VIRTIO_NET_F_MQ not negotiated

[Ladi Prosek]

On Mon, Dec 4, 2017 at 3:08 PM, Maxime Coquelin
<maxime.coquelin@redhat.com> wrote:
> Having QEMU started with mq=on but guest driver not negotiating
> VIRTIO_NET_F_MQ feature ends up in the vhost device to never
> start. Indeed, more queues are created in the vhost backend than
> configured.
>
> Guest drivers known to not advertise the VIRTIO_NET_F_MQ feature are
> iPXE and OVMF Virtio-net drivers.
>
> Queues are created because before starting the guest, QEMU sends
> VHOST_USER_SET_VRING_CALL requests for all queues declared in QEMU
> command line. Also, once Virtio features negotiated, QEMU sends
> VHOST_USER_SET_VRING_ENABLE requests to disable all but the first
> queue pair.
>
> This series fixes this by destroying all but first queue pair in
> the backend if VIRTIO_NET_F_MQ isn't negotiated.

The destroyed queue pairs will be re-created when an MQ-enabled driver
takes over later on, though, is that correct?

iPXE and OVMF virtio-net drivers will typically not be the last ones
driving the device. They will likely load an OS equipped with a driver
that negotiates the MQ feature. Thanks!

> First patches
> makes sure that VHOST_USER_SET_FEATURES request doesn't change
> Virtio features while the device is running, which should never
> happen as per the Virtio spec. This helps to make sure vitqueues
> aren't destroyed while being processed, but also protect from
> other illegal features changes (e.g. VIRTIO_NET_F_MRG_RXBUF).
>
> Maxime Coquelin (4):
>   vhost: prevent features to be changed while device is running
>   vhost: propagate VHOST_USER_SET_FEATURES handling error
>   vhost: extract virtqueue cleaning and freeing functions
>   vhost: destroy unused virtqueues when multiqueue not negotiated
>
>  lib/librte_vhost/vhost.c      | 22 ++++++++++++----------
>  lib/librte_vhost/vhost.h      |  3 +++
>  lib/librte_vhost/vhost_user.c | 40 ++++++++++++++++++++++++++++++++++++++--
>  3 files changed, 53 insertions(+), 12 deletions(-)
>
> --
> 2.14.3
>

Re: [dpdk-dev] [PATCH 0/4] Vhost: fix mq=on but VIRTIO_NET_F_MQ not negotiated

[Maxime Coquelin]

On 12/04/2017 03:27 PM, Ladi Prosek wrote:
> On Mon, Dec 4, 2017 at 3:08 PM, Maxime Coquelin
> <maxime.coquelin@redhat.com>  wrote:
>> Having QEMU started with mq=on but guest driver not negotiating
>> VIRTIO_NET_F_MQ feature ends up in the vhost device to never
>> start. Indeed, more queues are created in the vhost backend than
>> configured.
>>
>> Guest drivers known to not advertise the VIRTIO_NET_F_MQ feature are
>> iPXE and OVMF Virtio-net drivers.
>>
>> Queues are created because before starting the guest, QEMU sends
>> VHOST_USER_SET_VRING_CALL requests for all queues declared in QEMU
>> command line. Also, once Virtio features negotiated, QEMU sends
>> VHOST_USER_SET_VRING_ENABLE requests to disable all but the first
>> queue pair.
>>
>> This series fixes this by destroying all but first queue pair in
>> the backend if VIRTIO_NET_F_MQ isn't negotiated.
> The destroyed queue pairs will be re-created when an MQ-enabled driver
> takes over later on, though, is that correct?

Correct! When the new driver registers, QEMU sends
VHOST_USER_SET_VRING_ENABLE requests to all queues in order to enable
only the first queue pair, disabling all others queue pairs.

In QEMU, see virtio_net_set_queues() in hw/net/virtio-net.c

> iPXE and OVMF virtio-net drivers will typically not be the last ones
> driving the device. They will likely load an OS equipped with a driver
> that negotiates the MQ feature. Thanks!
Maxime