| Message ID | 20220321153037.3622127-13-alex.bennee@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | various virtio docs, fixes and tweaks | expand |
On Mon, Mar 21, 2022 at 03:30:36PM +0000, Alex Bennée wrote: > Previously we would silently suppress VHOST_USER_PROTOCOL_F_CONFIG > during the protocol negotiation if the QEMU stub hadn't implemented > the vhost_dev_config_notifier. However this isn't the only way we can > handle config messages, the existing vdc->get/set_config can do this > as well. Could you give an example where the problem is encountered please? > Lightly re-factor the code to check for both potential methods and > instead of silently squashing the feature error out. It is unlikely > that a vhost-user backend expecting to handle CONFIG messages will > behave correctly if they never get sent. Hmm but are you sure? Most devices work mostly fine without CONFIG messages, there's a chance a backend set this flag just in case without much thought ... > Fixes: 1c3e5a2617 ("vhost-user: back SET/GET_CONFIG requests with a protocol feature") I'm not sure whether something is broken or this is a cleanup patch. Fixes tag means "if you have 1c3e5a2617 you should pick this patch", so cleanups don't need a fixes: tag. > Cc: Maxime Coquelin <maxime.coquelin@redhat.com> > Cc: Michael S. Tsirkin <mst@redhat.com> > Cc: Stefan Hajnoczi <stefanha@redhat.com> > Signed-off-by: Alex Bennée <alex.bennee@linaro.org> > > --- > - we can't check for get_config/set_config as the stack squashed vdev > - use vhost-user-state to transmit this > --- > include/hw/virtio/vhost-user.h | 1 + > hw/scsi/vhost-user-scsi.c | 1 + > hw/virtio/vhost-user.c | 46 ++++++++++++++++++++++++---------- > 3 files changed, 35 insertions(+), 13 deletions(-) > > diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h > index e44a41bb70..6e0e8a71a3 100644 > --- a/include/hw/virtio/vhost-user.h > +++ b/include/hw/virtio/vhost-user.h > @@ -22,6 +22,7 @@ typedef struct VhostUserState { > CharBackend *chr; > VhostUserHostNotifier notifier[VIRTIO_QUEUE_MAX]; > int memory_slots; > + bool supports_config; > } VhostUserState; > > bool vhost_user_init(VhostUserState *user, CharBackend *chr, Error **errp); > diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c > index 1b2f7eed98..9be21d07ee 100644 > --- a/hw/scsi/vhost-user-scsi.c > +++ b/hw/scsi/vhost-user-scsi.c > @@ -121,6 +121,7 @@ static void vhost_user_scsi_realize(DeviceState *dev, Error **errp) > vsc->dev.backend_features = 0; > vqs = vsc->dev.vqs; > > + s->vhost_user.supports_config = true; > ret = vhost_dev_init(&vsc->dev, &s->vhost_user, > VHOST_BACKEND_TYPE_USER, 0, errp); > if (ret < 0) { > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c > index b27b8c56e2..6ce082861b 100644 > --- a/hw/virtio/vhost-user.c > +++ b/hw/virtio/vhost-user.c > @@ -1949,14 +1949,15 @@ static int vhost_user_postcopy_notifier(NotifierWithReturn *notifier, > static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque, > Error **errp) > { > - uint64_t features, protocol_features, ram_slots; > + uint64_t features, ram_slots; > struct vhost_user *u; > + VhostUserState *vus = (VhostUserState *) opaque; > int err; > > assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER); > > u = g_new0(struct vhost_user, 1); > - u->user = opaque; > + u->user = vus; > u->dev = dev; > dev->opaque = u; > > @@ -1967,6 +1968,10 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque, > } > > if (virtio_has_feature(features, VHOST_USER_F_PROTOCOL_FEATURES)) { > + bool supports_f_config = vus->supports_config || > + (dev->config_ops && dev->config_ops->vhost_dev_config_notifier); > + uint64_t protocol_features; > + > dev->backend_features |= 1ULL << VHOST_USER_F_PROTOCOL_FEATURES; > > err = vhost_user_get_u64(dev, VHOST_USER_GET_PROTOCOL_FEATURES, > @@ -1976,19 +1981,34 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque, > return -EPROTO; > } > > - dev->protocol_features = > - protocol_features & VHOST_USER_PROTOCOL_FEATURE_MASK; > - > - if (!dev->config_ops || !dev->config_ops->vhost_dev_config_notifier) { > - /* Don't acknowledge CONFIG feature if device doesn't support it */ > - dev->protocol_features &= ~(1ULL << VHOST_USER_PROTOCOL_F_CONFIG); > - } else if (!(protocol_features & > - (1ULL << VHOST_USER_PROTOCOL_F_CONFIG))) { > - error_setg(errp, "Device expects VHOST_USER_PROTOCOL_F_CONFIG " > - "but backend does not support it."); > - return -EINVAL; > + /* > + * We will use all the protocol features we support - although > + * we suppress F_CONFIG if we know QEMUs internal code can not support > + * it. > + */ > + protocol_features &= VHOST_USER_PROTOCOL_FEATURE_MASK; > + > + if (supports_f_config) { > + if (!virtio_has_feature(protocol_features, > + VHOST_USER_PROTOCOL_F_CONFIG)) { > + error_setg(errp, "vhost-user device %s expecting " > + "VHOST_USER_PROTOCOL_F_CONFIG but the vhost-user backend does " > + "not support it.", dev->vdev->name); > + return -EPROTO; > + } > + } else { > + if (virtio_has_feature(protocol_features, > + VHOST_USER_PROTOCOL_F_CONFIG)) { > + warn_reportf_err(*errp, "vhost-user backend supports " > + "VHOST_USER_PROTOCOL_F_CONFIG for " > + "device %s but QEMU does not.", > + dev->vdev->name); > + protocol_features &= ~(1ULL << VHOST_USER_PROTOCOL_F_CONFIG); > + } > } > > + /* final set of protocol features */ > + dev->protocol_features = protocol_features; > err = vhost_user_set_protocol_features(dev, dev->protocol_features); > if (err < 0) { > error_setg_errno(errp, EPROTO, "vhost_backend_init failed"); > -- > 2.30.2
"Michael S. Tsirkin" <mst@redhat.com> writes: > On Mon, Mar 21, 2022 at 03:30:36PM +0000, Alex Bennée wrote: >> Previously we would silently suppress VHOST_USER_PROTOCOL_F_CONFIG >> during the protocol negotiation if the QEMU stub hadn't implemented >> the vhost_dev_config_notifier. However this isn't the only way we can >> handle config messages, the existing vdc->get/set_config can do this >> as well. > > Could you give an example where the problem is encountered please? Well I only came across it when I realised by rpmb implementation wasn't sending config updates to the vhost-user daemon because it only implemented set/get_config methods. I think vhost-user-scsi suffers from this but I'm not able to test it as it's not clear how to do it. The vhost-user-scsi daemon want to attach to real SCSI devices rather than a file for the block device. I guess I need to somehow add "fake" scsi nodes to my host system which SCSI commands can be passed to? When was the last time vhost-user-scsi was tested with anything? >> Lightly re-factor the code to check for both potential methods and >> instead of silently squashing the feature error out. It is unlikely >> that a vhost-user backend expecting to handle CONFIG messages will >> behave correctly if they never get sent. > > Hmm but are you sure? Most devices work mostly fine without CONFIG > messages, there's a chance a backend set this flag just in case > without much thought ... But that would be a bug right? Certainly a mismatch if something really does want to see config messages. Again RPMB needs this because it's the vhost-user daemon that knows the size of the device. >> Fixes: 1c3e5a2617 ("vhost-user: back SET/GET_CONFIG requests with a protocol feature") > > I'm not sure whether something is broken or this is a cleanup patch. > Fixes tag means "if you have 1c3e5a2617 you should pick this patch", so > cleanups don't need a fixes: tag. No I think it's broken, we just didn't notice because as you say most devices don't need to care. > > >> Cc: Maxime Coquelin <maxime.coquelin@redhat.com> >> Cc: Michael S. Tsirkin <mst@redhat.com> >> Cc: Stefan Hajnoczi <stefanha@redhat.com> >> Signed-off-by: Alex Bennée <alex.bennee@linaro.org> >> >> --- >> - we can't check for get_config/set_config as the stack squashed vdev >> - use vhost-user-state to transmit this >> --- >> include/hw/virtio/vhost-user.h | 1 + >> hw/scsi/vhost-user-scsi.c | 1 + >> hw/virtio/vhost-user.c | 46 ++++++++++++++++++++++++---------- >> 3 files changed, 35 insertions(+), 13 deletions(-) >> >> diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h >> index e44a41bb70..6e0e8a71a3 100644 >> --- a/include/hw/virtio/vhost-user.h >> +++ b/include/hw/virtio/vhost-user.h >> @@ -22,6 +22,7 @@ typedef struct VhostUserState { >> CharBackend *chr; >> VhostUserHostNotifier notifier[VIRTIO_QUEUE_MAX]; >> int memory_slots; >> + bool supports_config; >> } VhostUserState; >> >> bool vhost_user_init(VhostUserState *user, CharBackend *chr, Error **errp); >> diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c >> index 1b2f7eed98..9be21d07ee 100644 >> --- a/hw/scsi/vhost-user-scsi.c >> +++ b/hw/scsi/vhost-user-scsi.c >> @@ -121,6 +121,7 @@ static void vhost_user_scsi_realize(DeviceState *dev, Error **errp) >> vsc->dev.backend_features = 0; >> vqs = vsc->dev.vqs; >> >> + s->vhost_user.supports_config = true; >> ret = vhost_dev_init(&vsc->dev, &s->vhost_user, >> VHOST_BACKEND_TYPE_USER, 0, errp); >> if (ret < 0) { >> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c >> index b27b8c56e2..6ce082861b 100644 >> --- a/hw/virtio/vhost-user.c >> +++ b/hw/virtio/vhost-user.c >> @@ -1949,14 +1949,15 @@ static int vhost_user_postcopy_notifier(NotifierWithReturn *notifier, >> static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque, >> Error **errp) >> { >> - uint64_t features, protocol_features, ram_slots; >> + uint64_t features, ram_slots; >> struct vhost_user *u; >> + VhostUserState *vus = (VhostUserState *) opaque; >> int err; >> >> assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER); >> >> u = g_new0(struct vhost_user, 1); >> - u->user = opaque; >> + u->user = vus; >> u->dev = dev; >> dev->opaque = u; >> >> @@ -1967,6 +1968,10 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque, >> } >> >> if (virtio_has_feature(features, VHOST_USER_F_PROTOCOL_FEATURES)) { >> + bool supports_f_config = vus->supports_config || >> + (dev->config_ops && dev->config_ops->vhost_dev_config_notifier); >> + uint64_t protocol_features; >> + >> dev->backend_features |= 1ULL << VHOST_USER_F_PROTOCOL_FEATURES; >> >> err = vhost_user_get_u64(dev, VHOST_USER_GET_PROTOCOL_FEATURES, >> @@ -1976,19 +1981,34 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque, >> return -EPROTO; >> } >> >> - dev->protocol_features = >> - protocol_features & VHOST_USER_PROTOCOL_FEATURE_MASK; >> - >> - if (!dev->config_ops || !dev->config_ops->vhost_dev_config_notifier) { >> - /* Don't acknowledge CONFIG feature if device doesn't support it */ >> - dev->protocol_features &= ~(1ULL << VHOST_USER_PROTOCOL_F_CONFIG); >> - } else if (!(protocol_features & >> - (1ULL << VHOST_USER_PROTOCOL_F_CONFIG))) { >> - error_setg(errp, "Device expects VHOST_USER_PROTOCOL_F_CONFIG " >> - "but backend does not support it."); >> - return -EINVAL; >> + /* >> + * We will use all the protocol features we support - although >> + * we suppress F_CONFIG if we know QEMUs internal code can not support >> + * it. >> + */ >> + protocol_features &= VHOST_USER_PROTOCOL_FEATURE_MASK; >> + >> + if (supports_f_config) { >> + if (!virtio_has_feature(protocol_features, >> + VHOST_USER_PROTOCOL_F_CONFIG)) { >> + error_setg(errp, "vhost-user device %s expecting " >> + "VHOST_USER_PROTOCOL_F_CONFIG but the vhost-user backend does " >> + "not support it.", dev->vdev->name); >> + return -EPROTO; >> + } >> + } else { >> + if (virtio_has_feature(protocol_features, >> + VHOST_USER_PROTOCOL_F_CONFIG)) { >> + warn_reportf_err(*errp, "vhost-user backend supports " >> + "VHOST_USER_PROTOCOL_F_CONFIG for " >> + "device %s but QEMU does not.", >> + dev->vdev->name); >> + protocol_features &= ~(1ULL << VHOST_USER_PROTOCOL_F_CONFIG); >> + } >> } >> >> + /* final set of protocol features */ >> + dev->protocol_features = protocol_features; >> err = vhost_user_set_protocol_features(dev, dev->protocol_features); >> if (err < 0) { >> error_setg_errno(errp, EPROTO, "vhost_backend_init failed"); >> -- >> 2.30.2
On Tue, Mar 22, 2022 at 03:54:32PM +0000, Alex Bennée wrote: > > "Michael S. Tsirkin" <mst@redhat.com> writes: > > > On Mon, Mar 21, 2022 at 03:30:36PM +0000, Alex Bennée wrote: > >> Previously we would silently suppress VHOST_USER_PROTOCOL_F_CONFIG > >> during the protocol negotiation if the QEMU stub hadn't implemented > >> the vhost_dev_config_notifier. However this isn't the only way we can > >> handle config messages, the existing vdc->get/set_config can do this > >> as well. > > > > Could you give an example where the problem is encountered please? > > Well I only came across it when I realised by rpmb implementation wasn't > sending config updates to the vhost-user daemon because it only > implemented set/get_config methods. > > I think vhost-user-scsi suffers from this but I'm not able to test it as > it's not clear how to do it. The vhost-user-scsi daemon want to attach > to real SCSI devices rather than a file for the block device. I guess I > need to somehow add "fake" scsi nodes to my host system which SCSI > commands can be passed to? > > When was the last time vhost-user-scsi was tested with anything? It's for passthrough mostly, yes. I think you can use tcm_loop on top of loopback on top of a file. Didn't try myself. > >> Lightly re-factor the code to check for both potential methods and > >> instead of silently squashing the feature error out. It is unlikely > >> that a vhost-user backend expecting to handle CONFIG messages will > >> behave correctly if they never get sent. > > > > Hmm but are you sure? Most devices work mostly fine without CONFIG > > messages, there's a chance a backend set this flag just in case > > without much thought ... > > But that would be a bug right? Certainly a mismatch if something really > does want to see config messages. Again RPMB needs this because it's the > vhost-user daemon that knows the size of the device. Could you pls clarify how do you create a config that's broken with RPMB? > >> Fixes: 1c3e5a2617 ("vhost-user: back SET/GET_CONFIG requests with a protocol feature") > > > > I'm not sure whether something is broken or this is a cleanup patch. > > Fixes tag means "if you have 1c3e5a2617 you should pick this patch", so > > cleanups don't need a fixes: tag. > > No I think it's broken, we just didn't notice because as you say most > devices don't need to care. I was mostly asking about the fixes tag. If no existing user cares then it's best to avoid the fixes tag, it's a hint for backporters which versions need the patch. > > > > > >> Cc: Maxime Coquelin <maxime.coquelin@redhat.com> > >> Cc: Michael S. Tsirkin <mst@redhat.com> > >> Cc: Stefan Hajnoczi <stefanha@redhat.com> > >> Signed-off-by: Alex Bennée <alex.bennee@linaro.org> > >> > >> --- > >> - we can't check for get_config/set_config as the stack squashed vdev > >> - use vhost-user-state to transmit this > >> --- > >> include/hw/virtio/vhost-user.h | 1 + > >> hw/scsi/vhost-user-scsi.c | 1 + > >> hw/virtio/vhost-user.c | 46 ++++++++++++++++++++++++---------- > >> 3 files changed, 35 insertions(+), 13 deletions(-) > >> > >> diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h > >> index e44a41bb70..6e0e8a71a3 100644 > >> --- a/include/hw/virtio/vhost-user.h > >> +++ b/include/hw/virtio/vhost-user.h > >> @@ -22,6 +22,7 @@ typedef struct VhostUserState { > >> CharBackend *chr; > >> VhostUserHostNotifier notifier[VIRTIO_QUEUE_MAX]; > >> int memory_slots; > >> + bool supports_config; > >> } VhostUserState; > >> > >> bool vhost_user_init(VhostUserState *user, CharBackend *chr, Error **errp); > >> diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c > >> index 1b2f7eed98..9be21d07ee 100644 > >> --- a/hw/scsi/vhost-user-scsi.c > >> +++ b/hw/scsi/vhost-user-scsi.c > >> @@ -121,6 +121,7 @@ static void vhost_user_scsi_realize(DeviceState *dev, Error **errp) > >> vsc->dev.backend_features = 0; > >> vqs = vsc->dev.vqs; > >> > >> + s->vhost_user.supports_config = true; > >> ret = vhost_dev_init(&vsc->dev, &s->vhost_user, > >> VHOST_BACKEND_TYPE_USER, 0, errp); > >> if (ret < 0) { > >> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c > >> index b27b8c56e2..6ce082861b 100644 > >> --- a/hw/virtio/vhost-user.c > >> +++ b/hw/virtio/vhost-user.c > >> @@ -1949,14 +1949,15 @@ static int vhost_user_postcopy_notifier(NotifierWithReturn *notifier, > >> static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque, > >> Error **errp) > >> { > >> - uint64_t features, protocol_features, ram_slots; > >> + uint64_t features, ram_slots; > >> struct vhost_user *u; > >> + VhostUserState *vus = (VhostUserState *) opaque; > >> int err; > >> > >> assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER); > >> > >> u = g_new0(struct vhost_user, 1); > >> - u->user = opaque; > >> + u->user = vus; > >> u->dev = dev; > >> dev->opaque = u; > >> > >> @@ -1967,6 +1968,10 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque, > >> } > >> > >> if (virtio_has_feature(features, VHOST_USER_F_PROTOCOL_FEATURES)) { > >> + bool supports_f_config = vus->supports_config || > >> + (dev->config_ops && dev->config_ops->vhost_dev_config_notifier); > >> + uint64_t protocol_features; > >> + > >> dev->backend_features |= 1ULL << VHOST_USER_F_PROTOCOL_FEATURES; > >> > >> err = vhost_user_get_u64(dev, VHOST_USER_GET_PROTOCOL_FEATURES, > >> @@ -1976,19 +1981,34 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque, > >> return -EPROTO; > >> } > >> > >> - dev->protocol_features = > >> - protocol_features & VHOST_USER_PROTOCOL_FEATURE_MASK; > >> - > >> - if (!dev->config_ops || !dev->config_ops->vhost_dev_config_notifier) { > >> - /* Don't acknowledge CONFIG feature if device doesn't support it */ > >> - dev->protocol_features &= ~(1ULL << VHOST_USER_PROTOCOL_F_CONFIG); > >> - } else if (!(protocol_features & > >> - (1ULL << VHOST_USER_PROTOCOL_F_CONFIG))) { > >> - error_setg(errp, "Device expects VHOST_USER_PROTOCOL_F_CONFIG " > >> - "but backend does not support it."); > >> - return -EINVAL; > >> + /* > >> + * We will use all the protocol features we support - although > >> + * we suppress F_CONFIG if we know QEMUs internal code can not support > >> + * it. > >> + */ > >> + protocol_features &= VHOST_USER_PROTOCOL_FEATURE_MASK; > >> + > >> + if (supports_f_config) { > >> + if (!virtio_has_feature(protocol_features, > >> + VHOST_USER_PROTOCOL_F_CONFIG)) { > >> + error_setg(errp, "vhost-user device %s expecting " > >> + "VHOST_USER_PROTOCOL_F_CONFIG but the vhost-user backend does " > >> + "not support it.", dev->vdev->name); > >> + return -EPROTO; > >> + } > >> + } else { > >> + if (virtio_has_feature(protocol_features, > >> + VHOST_USER_PROTOCOL_F_CONFIG)) { > >> + warn_reportf_err(*errp, "vhost-user backend supports " > >> + "VHOST_USER_PROTOCOL_F_CONFIG for " > >> + "device %s but QEMU does not.", > >> + dev->vdev->name); > >> + protocol_features &= ~(1ULL << VHOST_USER_PROTOCOL_F_CONFIG); > >> + } > >> } > >> > >> + /* final set of protocol features */ > >> + dev->protocol_features = protocol_features; > >> err = vhost_user_set_protocol_features(dev, dev->protocol_features); > >> if (err < 0) { > >> error_setg_errno(errp, EPROTO, "vhost_backend_init failed"); > >> -- > >> 2.30.2 > > > -- > Alex Bennée
diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h index e44a41bb70..6e0e8a71a3 100644 --- a/include/hw/virtio/vhost-user.h +++ b/include/hw/virtio/vhost-user.h @@ -22,6 +22,7 @@ typedef struct VhostUserState { CharBackend *chr; VhostUserHostNotifier notifier[VIRTIO_QUEUE_MAX]; int memory_slots; + bool supports_config; } VhostUserState; bool vhost_user_init(VhostUserState *user, CharBackend *chr, Error **errp); diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c index 1b2f7eed98..9be21d07ee 100644 --- a/hw/scsi/vhost-user-scsi.c +++ b/hw/scsi/vhost-user-scsi.c @@ -121,6 +121,7 @@ static void vhost_user_scsi_realize(DeviceState *dev, Error **errp) vsc->dev.backend_features = 0; vqs = vsc->dev.vqs; + s->vhost_user.supports_config = true; ret = vhost_dev_init(&vsc->dev, &s->vhost_user, VHOST_BACKEND_TYPE_USER, 0, errp); if (ret < 0) { diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c index b27b8c56e2..6ce082861b 100644 --- a/hw/virtio/vhost-user.c +++ b/hw/virtio/vhost-user.c @@ -1949,14 +1949,15 @@ static int vhost_user_postcopy_notifier(NotifierWithReturn *notifier, static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque, Error **errp) { - uint64_t features, protocol_features, ram_slots; + uint64_t features, ram_slots; struct vhost_user *u; + VhostUserState *vus = (VhostUserState *) opaque; int err; assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER); u = g_new0(struct vhost_user, 1); - u->user = opaque; + u->user = vus; u->dev = dev; dev->opaque = u; @@ -1967,6 +1968,10 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque, } if (virtio_has_feature(features, VHOST_USER_F_PROTOCOL_FEATURES)) { + bool supports_f_config = vus->supports_config || + (dev->config_ops && dev->config_ops->vhost_dev_config_notifier); + uint64_t protocol_features; + dev->backend_features |= 1ULL << VHOST_USER_F_PROTOCOL_FEATURES; err = vhost_user_get_u64(dev, VHOST_USER_GET_PROTOCOL_FEATURES, @@ -1976,19 +1981,34 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque, return -EPROTO; } - dev->protocol_features = - protocol_features & VHOST_USER_PROTOCOL_FEATURE_MASK; - - if (!dev->config_ops || !dev->config_ops->vhost_dev_config_notifier) { - /* Don't acknowledge CONFIG feature if device doesn't support it */ - dev->protocol_features &= ~(1ULL << VHOST_USER_PROTOCOL_F_CONFIG); - } else if (!(protocol_features & - (1ULL << VHOST_USER_PROTOCOL_F_CONFIG))) { - error_setg(errp, "Device expects VHOST_USER_PROTOCOL_F_CONFIG " - "but backend does not support it."); - return -EINVAL; + /* + * We will use all the protocol features we support - although + * we suppress F_CONFIG if we know QEMUs internal code can not support + * it. + */ + protocol_features &= VHOST_USER_PROTOCOL_FEATURE_MASK; + + if (supports_f_config) { + if (!virtio_has_feature(protocol_features, + VHOST_USER_PROTOCOL_F_CONFIG)) { + error_setg(errp, "vhost-user device %s expecting " + "VHOST_USER_PROTOCOL_F_CONFIG but the vhost-user backend does " + "not support it.", dev->vdev->name); + return -EPROTO; + } + } else { + if (virtio_has_feature(protocol_features, + VHOST_USER_PROTOCOL_F_CONFIG)) { + warn_reportf_err(*errp, "vhost-user backend supports " + "VHOST_USER_PROTOCOL_F_CONFIG for " + "device %s but QEMU does not.", + dev->vdev->name); + protocol_features &= ~(1ULL << VHOST_USER_PROTOCOL_F_CONFIG); + } } + /* final set of protocol features */ + dev->protocol_features = protocol_features; err = vhost_user_set_protocol_features(dev, dev->protocol_features); if (err < 0) { error_setg_errno(errp, EPROTO, "vhost_backend_init failed");
Previously we would silently suppress VHOST_USER_PROTOCOL_F_CONFIG during the protocol negotiation if the QEMU stub hadn't implemented the vhost_dev_config_notifier. However this isn't the only way we can handle config messages, the existing vdc->get/set_config can do this as well. Lightly re-factor the code to check for both potential methods and instead of silently squashing the feature error out. It is unlikely that a vhost-user backend expecting to handle CONFIG messages will behave correctly if they never get sent. Fixes: 1c3e5a2617 ("vhost-user: back SET/GET_CONFIG requests with a protocol feature") Cc: Maxime Coquelin <maxime.coquelin@redhat.com> Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Alex Bennée <alex.bennee@linaro.org> --- - we can't check for get_config/set_config as the stack squashed vdev - use vhost-user-state to transmit this --- include/hw/virtio/vhost-user.h | 1 + hw/scsi/vhost-user-scsi.c | 1 + hw/virtio/vhost-user.c | 46 ++++++++++++++++++++++++---------- 3 files changed, 35 insertions(+), 13 deletions(-)