Yajun Wu <yaj...@nvidia.com> writes:
> Hi Alex, > > With this change, VHOST_USER_F_PROTOCOL_FEATURES bit will be set to > backend for virtio block device (previously not). > > From https://www.qemu.org/docs/master/interop/vhost-user.html spec: > If VHOST_USER_F_PROTOCOL_FEATURES has not been negotiated, the ring starts > directly in the enabled state. > If VHOST_USER_F_PROTOCOL_FEATURES has been negotiated, the ring is > initialized in a disabled state and is enabled by > VHOST_USER_SET_VRING_ENABLE with parameter 1. > > Vhost-user-blk won't send out VHOST_USER_SET_VRING_ENABLE today. > Backend gets VHOST_USER_F_PROTOCOL_FEATURES negotiated and can't get > VHOST_USER_SET_VRING_ENABLE. > VQs keep in disabled state. If the backend advertises protocol features but the stub doesn't support it how does it get enabled? The testing I did was mostly by hand with the gpio backend and using the qtests. I Think we need to add some acceptance testing into avocado with some real daemons because I don't think we have enough coverage with the current qtest approach. > > Can you check on this scenario? > > Thanks > > -----Original Message----- > From: Qemu-devel <qemu-devel-bounces+yajunw=nvidia....@nongnu.org> On Behalf > Of Alex Bennée > Sent: Thursday, July 28, 2022 9:55 PM > To: qemu-devel@nongnu.org > Cc: m...@redhat.com; Alex Bennée <alex.ben...@linaro.org> > Subject: [PATCH v2 1/4] hw/virtio: incorporate backend features in features > > External email: Use caution opening links or attachments > > > There are some extra bits used over a vhost-user connection which are hidden > from the device itself. We need to set them here to ensure we enable things > like the protocol extensions. > > Currently net/vhost-user.c has it's own inscrutable way of persisting this > data but it really should live in the core vhost_user code. > > Signed-off-by: Alex Bennée <alex.ben...@linaro.org> > Message-Id: <20220726192150.2435175-7-alex.ben...@linaro.org> > --- > hw/virtio/vhost-user.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c index > 75b8df21a4..1936a44e82 100644 > --- a/hw/virtio/vhost-user.c > +++ b/hw/virtio/vhost-user.c > @@ -1460,7 +1460,14 @@ static int vhost_user_set_features(struct vhost_dev > *dev, > */ > bool log_enabled = features & (0x1ULL << VHOST_F_LOG_ALL); > > - return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features, > + /* > + * We need to include any extra backend only feature bits that > + * might be needed by our device. Currently this includes the > + * VHOST_USER_F_PROTOCOL_FEATURES bit for enabling protocol > + * features. > + */ > + return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, > + features | dev->backend_features, > log_enabled); } -- Alex Bennée
