libvhost-user implements several vring features without advertising
them. There is no way for the vhost-user master to detect support for
these features.
Things more or less work today because QEMU assumes the vhost-user
backend always implements certain feature bits like
VIRTIO_RING_F_EVENT_IDX. This is not documented anywhere.
This patch explicitly advertises features implemented in libvhost-user
so that the vhost-user master does not need to make undocumented
assumptions.
Feature bits that libvhost-user now advertises can be removed from
vhost-user-blk.c. Devices should not be responsible for advertising
vring feature bits, that is libvhost-user's job.
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
I have tested make check and virtiofsd.
---
contrib/libvhost-user/libvhost-user.c | 10 ++++++++++
contrib/vhost-user-blk/vhost-user-blk.c | 4 +---
2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-user/libvhost-user.c
index 3bca996c62..b43874ba12 100644
--- a/contrib/libvhost-user/libvhost-user.c
+++ b/contrib/libvhost-user/libvhost-user.c
@@ -495,6 +495,16 @@ static bool
vu_get_features_exec(VuDev *dev, VhostUserMsg *vmsg)
{
vmsg->payload.u64 =
+ /*
+ * The following VIRTIO feature bits are supported by our virtqueue
+ * implementation:
+ */
+ 1ULL << VIRTIO_F_NOTIFY_ON_EMPTY |
+ 1ULL << VIRTIO_RING_F_INDIRECT_DESC |
+ 1ULL << VIRTIO_RING_F_EVENT_IDX |
+ 1ULL << VIRTIO_F_VERSION_1 |
+
+ /* vhost-user feature bits */
1ULL << VHOST_F_LOG_ALL |
1ULL << VHOST_USER_F_PROTOCOL_FEATURES;
diff --git a/contrib/vhost-user-blk/vhost-user-blk.c b/contrib/vhost-user-blk/vhost-user-blk.c
index 6fd91c7e99..25eccd02b5 100644
--- a/contrib/vhost-user-blk/vhost-user-blk.c
+++ b/contrib/vhost-user-blk/vhost-user-blk.c
@@ -382,9 +382,7 @@ vub_get_features(VuDev *dev)
1ull << VIRTIO_BLK_F_DISCARD |
1ull << VIRTIO_BLK_F_WRITE_ZEROES |
#endif
- 1ull << VIRTIO_BLK_F_CONFIG_WCE |
- 1ull << VIRTIO_F_VERSION_1 |
- 1ull << VHOST_USER_F_PROTOCOL_FEATURES;
+ 1ull << VIRTIO_BLK_F_CONFIG_WCE;
if (vdev_blk->enable_ro) {
features |= 1ull << VIRTIO_BLK_F_RO;
--
2.25.4
Hi On Fri, May 29, 2020 at 6:13 PM Stefan Hajnoczi <stefanha@redhat.com> wrote: > > libvhost-user implements several vring features without advertising > them. There is no way for the vhost-user master to detect support for > these features. > > Things more or less work today because QEMU assumes the vhost-user > backend always implements certain feature bits like > VIRTIO_RING_F_EVENT_IDX. This is not documented anywhere. > > This patch explicitly advertises features implemented in libvhost-user > so that the vhost-user master does not need to make undocumented > assumptions. > > Feature bits that libvhost-user now advertises can be removed from > vhost-user-blk.c. Devices should not be responsible for advertising > vring feature bits, that is libvhost-user's job. > > Cc: Marc-André Lureau <marcandre.lureau@redhat.com> > Cc: Jason Wang <jasowang@redhat.com> > Cc: Michael S. Tsirkin <mst@redhat.com> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> > --- > I have tested make check and virtiofsd. > --- > contrib/libvhost-user/libvhost-user.c | 10 ++++++++++ > contrib/vhost-user-blk/vhost-user-blk.c | 4 +--- > 2 files changed, 11 insertions(+), 3 deletions(-) > > diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-user/libvhost-user.c > index 3bca996c62..b43874ba12 100644 > --- a/contrib/libvhost-user/libvhost-user.c > +++ b/contrib/libvhost-user/libvhost-user.c > @@ -495,6 +495,16 @@ static bool > vu_get_features_exec(VuDev *dev, VhostUserMsg *vmsg) > { > vmsg->payload.u64 = > + /* > + * The following VIRTIO feature bits are supported by our virtqueue > + * implementation: > + */ > + 1ULL << VIRTIO_F_NOTIFY_ON_EMPTY | > + 1ULL << VIRTIO_RING_F_INDIRECT_DESC | > + 1ULL << VIRTIO_RING_F_EVENT_IDX | > + 1ULL << VIRTIO_F_VERSION_1 | > + > + /* vhost-user feature bits */ > 1ULL << VHOST_F_LOG_ALL | > 1ULL << VHOST_USER_F_PROTOCOL_FEATURES; > > diff --git a/contrib/vhost-user-blk/vhost-user-blk.c b/contrib/vhost-user-blk/vhost-user-blk.c > index 6fd91c7e99..25eccd02b5 100644 > --- a/contrib/vhost-user-blk/vhost-user-blk.c > +++ b/contrib/vhost-user-blk/vhost-user-blk.c > @@ -382,9 +382,7 @@ vub_get_features(VuDev *dev) > 1ull << VIRTIO_BLK_F_DISCARD | > 1ull << VIRTIO_BLK_F_WRITE_ZEROES | > #endif > - 1ull << VIRTIO_BLK_F_CONFIG_WCE | > - 1ull << VIRTIO_F_VERSION_1 | > - 1ull << VHOST_USER_F_PROTOCOL_FEATURES; > + 1ull << VIRTIO_BLK_F_CONFIG_WCE; > > if (vdev_blk->enable_ro) { > features |= 1ull << VIRTIO_BLK_F_RO; > -- > 2.25.4 >
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