| Message ID | 20210719142138.24543-1-den-plotnikov@yandex-team.ru |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] vhost: make SET_VRING_ADDR, SET_FEATURES send replies | expand |
ping! On 19.07.2021 17:21, Denis Plotnikov wrote: > On vhost-user-blk migration, qemu normally sends a number of commands > to enable logging if VHOST_USER_PROTOCOL_F_LOG_SHMFD is negotiated. > Qemu sends VHOST_USER_SET_FEATURES to enable buffers logging and > VHOST_USER_SET_VRING_ADDR per each started ring to enable "used ring" > data logging. > The issue is that qemu doesn't wait for reply from the vhost daemon > for these commands which may result in races between qemu expectation > of logging starting and actual login starting in vhost daemon. > > The race can appear as follows: on migration setup, qemu enables dirty page > logging by sending VHOST_USER_SET_FEATURES. The command doesn't arrive to a > vhost-user-blk daemon immediately and the daemon needs some time to turn the > logging on internally. If qemu doesn't wait for reply, after sending the > command, qemu may start migrate memory pages to a destination. At this time, > the logging may not be actually turned on in the daemon but some guest pages, > which the daemon is about to write to, may have already been transferred > without logging to the destination. Since the logging wasn't turned on, > those pages won't be transferred again as dirty. So we may end up with > corrupted data on the destination. > The same scenario is applicable for "used ring" data logging, which is > turned on with VHOST_USER_SET_VRING_ADDR command. > > To resolve this issue, this patch makes qemu wait for the commands result > explicilty if VHOST_USER_PROTOCOL_F_REPLY_ACK is negotiated and > logging is enabled. > > Signed-off-by: Denis Plotnikov <den-plotnikov@yandex-team.ru> > --- > v1 -> v2: > * send reply only when logging is enabled [mst] > > v0 -> v1: > * send reply for SET_VRING_ADDR, SET_FEATURES only [mst] > > hw/virtio/vhost-user.c | 37 ++++++++++++++++++++++++++++++++++--- > 1 file changed, 34 insertions(+), 3 deletions(-) > > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c > index ee57abe04526..133588b3961e 100644 > --- a/hw/virtio/vhost-user.c > +++ b/hw/virtio/vhost-user.c > @@ -1095,6 +1095,11 @@ static int vhost_user_set_mem_table(struct vhost_dev *dev, > return 0; > } > > +static bool log_enabled(uint64_t features) > +{ > + return !!(features & (0x1ULL << VHOST_F_LOG_ALL)); > +} > + > static int vhost_user_set_vring_addr(struct vhost_dev *dev, > struct vhost_vring_addr *addr) > { > @@ -1105,10 +1110,21 @@ static int vhost_user_set_vring_addr(struct vhost_dev *dev, > .hdr.size = sizeof(msg.payload.addr), > }; > > + bool reply_supported = virtio_has_feature(dev->protocol_features, > + VHOST_USER_PROTOCOL_F_REPLY_ACK); > + > + if (reply_supported && log_enabled(msg.hdr.flags)) { > + msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; > + } > + > if (vhost_user_write(dev, &msg, NULL, 0) < 0) { > return -1; > } > > + if (msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK) { > + return process_message_reply(dev, &msg); > + } > + > return 0; > } > > @@ -1288,7 +1304,8 @@ static int vhost_user_set_vring_call(struct vhost_dev *dev, > return vhost_set_vring_file(dev, VHOST_USER_SET_VRING_CALL, file); > } > > -static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64) > +static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64, > + bool need_reply) > { > VhostUserMsg msg = { > .hdr.request = request, > @@ -1297,23 +1314,37 @@ static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64) > .hdr.size = sizeof(msg.payload.u64), > }; > > + if (need_reply) { > + bool reply_supported = virtio_has_feature(dev->protocol_features, > + VHOST_USER_PROTOCOL_F_REPLY_ACK); > + if (reply_supported) { > + msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; > + } > + } > + > if (vhost_user_write(dev, &msg, NULL, 0) < 0) { > return -1; > } > > + if (msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK) { > + return process_message_reply(dev, &msg); > + } > + > return 0; > } > > static int vhost_user_set_features(struct vhost_dev *dev, > uint64_t features) > { > - return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features); > + return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features, > + log_enabled(features)); > } > > static int vhost_user_set_protocol_features(struct vhost_dev *dev, > uint64_t features) > { > - return vhost_user_set_u64(dev, VHOST_USER_SET_PROTOCOL_FEATURES, features); > + return vhost_user_set_u64(dev, VHOST_USER_SET_PROTOCOL_FEATURES, features, > + false); > } > > static int vhost_user_get_u64(struct vhost_dev *dev, int request, uint64_t *u64)
On 23.07.2021 12:59, Denis Plotnikov wrote: > > ping! > > On 19.07.2021 17:21, Denis Plotnikov wrote: >> On vhost-user-blk migration, qemu normally sends a number of commands >> to enable logging if VHOST_USER_PROTOCOL_F_LOG_SHMFD is negotiated. >> Qemu sends VHOST_USER_SET_FEATURES to enable buffers logging and >> VHOST_USER_SET_VRING_ADDR per each started ring to enable "used ring" >> data logging. >> The issue is that qemu doesn't wait for reply from the vhost daemon >> for these commands which may result in races between qemu expectation >> of logging starting and actual login starting in vhost daemon. >> >> The race can appear as follows: on migration setup, qemu enables dirty page >> logging by sending VHOST_USER_SET_FEATURES. The command doesn't arrive to a >> vhost-user-blk daemon immediately and the daemon needs some time to turn the >> logging on internally. If qemu doesn't wait for reply, after sending the >> command, qemu may start migrate memory pages to a destination. At this time, >> the logging may not be actually turned on in the daemon but some guest pages, >> which the daemon is about to write to, may have already been transferred >> without logging to the destination. Since the logging wasn't turned on, >> those pages won't be transferred again as dirty. So we may end up with >> corrupted data on the destination. >> The same scenario is applicable for "used ring" data logging, which is >> turned on with VHOST_USER_SET_VRING_ADDR command. >> >> To resolve this issue, this patch makes qemu wait for the commands result >> explicilty if VHOST_USER_PROTOCOL_F_REPLY_ACK is negotiated and >> logging is enabled. >> >> Signed-off-by: Denis Plotnikov<den-plotnikov@yandex-team.ru> >> --- >> v1 -> v2: >> * send reply only when logging is enabled [mst] >> >> v0 -> v1: >> * send reply for SET_VRING_ADDR, SET_FEATURES only [mst] >> >> hw/virtio/vhost-user.c | 37 ++++++++++++++++++++++++++++++++++--- >> 1 file changed, 34 insertions(+), 3 deletions(-) >> >> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c >> index ee57abe04526..133588b3961e 100644 >> --- a/hw/virtio/vhost-user.c >> +++ b/hw/virtio/vhost-user.c >> @@ -1095,6 +1095,11 @@ static int vhost_user_set_mem_table(struct vhost_dev *dev, >> return 0; >> } >> >> +static bool log_enabled(uint64_t features) >> +{ >> + return !!(features & (0x1ULL << VHOST_F_LOG_ALL)); >> +} >> + >> static int vhost_user_set_vring_addr(struct vhost_dev *dev, >> struct vhost_vring_addr *addr) >> { >> @@ -1105,10 +1110,21 @@ static int vhost_user_set_vring_addr(struct vhost_dev *dev, >> .hdr.size = sizeof(msg.payload.addr), >> }; >> >> + bool reply_supported = virtio_has_feature(dev->protocol_features, >> + VHOST_USER_PROTOCOL_F_REPLY_ACK); >> + >> + if (reply_supported && log_enabled(msg.hdr.flags)) { >> + msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; >> + } >> + >> if (vhost_user_write(dev, &msg, NULL, 0) < 0) { >> return -1; >> } >> >> + if (msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK) { >> + return process_message_reply(dev, &msg); >> + } >> + >> return 0; >> } >> >> @@ -1288,7 +1304,8 @@ static int vhost_user_set_vring_call(struct vhost_dev *dev, >> return vhost_set_vring_file(dev, VHOST_USER_SET_VRING_CALL, file); >> } >> >> -static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64) >> +static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64, >> + bool need_reply) >> { >> VhostUserMsg msg = { >> .hdr.request = request, >> @@ -1297,23 +1314,37 @@ static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64) >> .hdr.size = sizeof(msg.payload.u64), >> }; >> >> + if (need_reply) { >> + bool reply_supported = virtio_has_feature(dev->protocol_features, >> + VHOST_USER_PROTOCOL_F_REPLY_ACK); >> + if (reply_supported) { >> + msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; >> + } >> + } >> + >> if (vhost_user_write(dev, &msg, NULL, 0) < 0) { >> return -1; >> } >> >> + if (msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK) { >> + return process_message_reply(dev, &msg); >> + } >> + >> return 0; >> } >> >> static int vhost_user_set_features(struct vhost_dev *dev, >> uint64_t features) >> { >> - return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features); >> + return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features, >> + log_enabled(features)); >> } >> >> static int vhost_user_set_protocol_features(struct vhost_dev *dev, >> uint64_t features) >> { >> - return vhost_user_set_u64(dev, VHOST_USER_SET_PROTOCOL_FEATURES, features); >> + return vhost_user_set_u64(dev, VHOST_USER_SET_PROTOCOL_FEATURES, features, >> + false); >> } >> >> static int vhost_user_get_u64(struct vhost_dev *dev, int request, uint64_t *u64)
Cc more ppl. On 7/29/21 12:56 PM, Denis Plotnikov wrote: > > On 23.07.2021 12:59, Denis Plotnikov wrote: >> >> ping! >> >> On 19.07.2021 17:21, Denis Plotnikov wrote: >>> On vhost-user-blk migration, qemu normally sends a number of commands >>> to enable logging if VHOST_USER_PROTOCOL_F_LOG_SHMFD is negotiated. >>> Qemu sends VHOST_USER_SET_FEATURES to enable buffers logging and >>> VHOST_USER_SET_VRING_ADDR per each started ring to enable "used ring" >>> data logging. >>> The issue is that qemu doesn't wait for reply from the vhost daemon >>> for these commands which may result in races between qemu expectation >>> of logging starting and actual login starting in vhost daemon. >>> >>> The race can appear as follows: on migration setup, qemu enables dirty page >>> logging by sending VHOST_USER_SET_FEATURES. The command doesn't arrive to a >>> vhost-user-blk daemon immediately and the daemon needs some time to turn the >>> logging on internally. If qemu doesn't wait for reply, after sending the >>> command, qemu may start migrate memory pages to a destination. At this time, >>> the logging may not be actually turned on in the daemon but some guest pages, >>> which the daemon is about to write to, may have already been transferred >>> without logging to the destination. Since the logging wasn't turned on, >>> those pages won't be transferred again as dirty. So we may end up with >>> corrupted data on the destination. >>> The same scenario is applicable for "used ring" data logging, which is >>> turned on with VHOST_USER_SET_VRING_ADDR command. >>> >>> To resolve this issue, this patch makes qemu wait for the commands result >>> explicilty if VHOST_USER_PROTOCOL_F_REPLY_ACK is negotiated and >>> logging is enabled. >>> >>> Signed-off-by: Denis Plotnikov <den-plotnikov@yandex-team.ru> >>> --- >>> v1 -> v2: >>> * send reply only when logging is enabled [mst] >>> >>> v0 -> v1: >>> * send reply for SET_VRING_ADDR, SET_FEATURES only [mst] >>> >>> hw/virtio/vhost-user.c | 37 ++++++++++++++++++++++++++++++++++--- >>> 1 file changed, 34 insertions(+), 3 deletions(-) >>> >>> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c >>> index ee57abe04526..133588b3961e 100644 >>> --- a/hw/virtio/vhost-user.c >>> +++ b/hw/virtio/vhost-user.c >>> @@ -1095,6 +1095,11 @@ static int vhost_user_set_mem_table(struct vhost_dev *dev, >>> return 0; >>> } >>> >>> +static bool log_enabled(uint64_t features) >>> +{ >>> + return !!(features & (0x1ULL << VHOST_F_LOG_ALL)); >>> +} >>> + >>> static int vhost_user_set_vring_addr(struct vhost_dev *dev, >>> struct vhost_vring_addr *addr) >>> { >>> @@ -1105,10 +1110,21 @@ static int vhost_user_set_vring_addr(struct vhost_dev *dev, >>> .hdr.size = sizeof(msg.payload.addr), >>> }; >>> >>> + bool reply_supported = virtio_has_feature(dev->protocol_features, >>> + VHOST_USER_PROTOCOL_F_REPLY_ACK); >>> + >>> + if (reply_supported && log_enabled(msg.hdr.flags)) { >>> + msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; >>> + } >>> + >>> if (vhost_user_write(dev, &msg, NULL, 0) < 0) { >>> return -1; >>> } >>> >>> + if (msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK) { >>> + return process_message_reply(dev, &msg); >>> + } >>> + >>> return 0; >>> } >>> >>> @@ -1288,7 +1304,8 @@ static int vhost_user_set_vring_call(struct vhost_dev *dev, >>> return vhost_set_vring_file(dev, VHOST_USER_SET_VRING_CALL, file); >>> } >>> >>> -static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64) >>> +static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64, >>> + bool need_reply) >>> { >>> VhostUserMsg msg = { >>> .hdr.request = request, >>> @@ -1297,23 +1314,37 @@ static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64) >>> .hdr.size = sizeof(msg.payload.u64), >>> }; >>> >>> + if (need_reply) { >>> + bool reply_supported = virtio_has_feature(dev->protocol_features, >>> + VHOST_USER_PROTOCOL_F_REPLY_ACK); >>> + if (reply_supported) { >>> + msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; >>> + } >>> + } >>> + >>> if (vhost_user_write(dev, &msg, NULL, 0) < 0) { >>> return -1; >>> } >>> >>> + if (msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK) { >>> + return process_message_reply(dev, &msg); >>> + } >>> + >>> return 0; >>> } >>> >>> static int vhost_user_set_features(struct vhost_dev *dev, >>> uint64_t features) >>> { >>> - return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features); >>> + return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features, >>> + log_enabled(features)); >>> } >>> >>> static int vhost_user_set_protocol_features(struct vhost_dev *dev, >>> uint64_t features) >>> { >>> - return vhost_user_set_u64(dev, VHOST_USER_SET_PROTOCOL_FEATURES, features); >>> + return vhost_user_set_u64(dev, VHOST_USER_SET_PROTOCOL_FEATURES, features, >>> + false); >>> } >>> >>> static int vhost_user_get_u64(struct vhost_dev *dev, int request, uint64_t *u64)
On Thu, Jul 29, 2021 at 02:53:53PM +0200, Philippe Mathieu-Daudé wrote: > Cc more ppl. This needs to go through Michael Tsirkin's tree. Stefan > > On 7/29/21 12:56 PM, Denis Plotnikov wrote: > > > > On 23.07.2021 12:59, Denis Plotnikov wrote: > >> > >> ping! > >> > >> On 19.07.2021 17:21, Denis Plotnikov wrote: > >>> On vhost-user-blk migration, qemu normally sends a number of commands > >>> to enable logging if VHOST_USER_PROTOCOL_F_LOG_SHMFD is negotiated. > >>> Qemu sends VHOST_USER_SET_FEATURES to enable buffers logging and > >>> VHOST_USER_SET_VRING_ADDR per each started ring to enable "used ring" > >>> data logging. > >>> The issue is that qemu doesn't wait for reply from the vhost daemon > >>> for these commands which may result in races between qemu expectation > >>> of logging starting and actual login starting in vhost daemon. > >>> > >>> The race can appear as follows: on migration setup, qemu enables dirty page > >>> logging by sending VHOST_USER_SET_FEATURES. The command doesn't arrive to a > >>> vhost-user-blk daemon immediately and the daemon needs some time to turn the > >>> logging on internally. If qemu doesn't wait for reply, after sending the > >>> command, qemu may start migrate memory pages to a destination. At this time, > >>> the logging may not be actually turned on in the daemon but some guest pages, > >>> which the daemon is about to write to, may have already been transferred > >>> without logging to the destination. Since the logging wasn't turned on, > >>> those pages won't be transferred again as dirty. So we may end up with > >>> corrupted data on the destination. > >>> The same scenario is applicable for "used ring" data logging, which is > >>> turned on with VHOST_USER_SET_VRING_ADDR command. > >>> > >>> To resolve this issue, this patch makes qemu wait for the commands result > >>> explicilty if VHOST_USER_PROTOCOL_F_REPLY_ACK is negotiated and > >>> logging is enabled. > >>> > >>> Signed-off-by: Denis Plotnikov <den-plotnikov@yandex-team.ru> > >>> --- > >>> v1 -> v2: > >>> * send reply only when logging is enabled [mst] > >>> > >>> v0 -> v1: > >>> * send reply for SET_VRING_ADDR, SET_FEATURES only [mst] > >>> > >>> hw/virtio/vhost-user.c | 37 ++++++++++++++++++++++++++++++++++--- > >>> 1 file changed, 34 insertions(+), 3 deletions(-) > >>> > >>> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c > >>> index ee57abe04526..133588b3961e 100644 > >>> --- a/hw/virtio/vhost-user.c > >>> +++ b/hw/virtio/vhost-user.c > >>> @@ -1095,6 +1095,11 @@ static int vhost_user_set_mem_table(struct vhost_dev *dev, > >>> return 0; > >>> } > >>> > >>> +static bool log_enabled(uint64_t features) > >>> +{ > >>> + return !!(features & (0x1ULL << VHOST_F_LOG_ALL)); > >>> +} > >>> + > >>> static int vhost_user_set_vring_addr(struct vhost_dev *dev, > >>> struct vhost_vring_addr *addr) > >>> { > >>> @@ -1105,10 +1110,21 @@ static int vhost_user_set_vring_addr(struct vhost_dev *dev, > >>> .hdr.size = sizeof(msg.payload.addr), > >>> }; > >>> > >>> + bool reply_supported = virtio_has_feature(dev->protocol_features, > >>> + VHOST_USER_PROTOCOL_F_REPLY_ACK); > >>> + > >>> + if (reply_supported && log_enabled(msg.hdr.flags)) { > >>> + msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; > >>> + } > >>> + > >>> if (vhost_user_write(dev, &msg, NULL, 0) < 0) { > >>> return -1; > >>> } > >>> > >>> + if (msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK) { > >>> + return process_message_reply(dev, &msg); > >>> + } > >>> + > >>> return 0; > >>> } > >>> > >>> @@ -1288,7 +1304,8 @@ static int vhost_user_set_vring_call(struct vhost_dev *dev, > >>> return vhost_set_vring_file(dev, VHOST_USER_SET_VRING_CALL, file); > >>> } > >>> > >>> -static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64) > >>> +static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64, > >>> + bool need_reply) > >>> { > >>> VhostUserMsg msg = { > >>> .hdr.request = request, > >>> @@ -1297,23 +1314,37 @@ static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64) > >>> .hdr.size = sizeof(msg.payload.u64), > >>> }; > >>> > >>> + if (need_reply) { > >>> + bool reply_supported = virtio_has_feature(dev->protocol_features, > >>> + VHOST_USER_PROTOCOL_F_REPLY_ACK); > >>> + if (reply_supported) { > >>> + msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; > >>> + } > >>> + } > >>> + > >>> if (vhost_user_write(dev, &msg, NULL, 0) < 0) { > >>> return -1; > >>> } > >>> > >>> + if (msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK) { > >>> + return process_message_reply(dev, &msg); > >>> + } > >>> + > >>> return 0; > >>> } > >>> > >>> static int vhost_user_set_features(struct vhost_dev *dev, > >>> uint64_t features) > >>> { > >>> - return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features); > >>> + return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features, > >>> + log_enabled(features)); > >>> } > >>> > >>> static int vhost_user_set_protocol_features(struct vhost_dev *dev, > >>> uint64_t features) > >>> { > >>> - return vhost_user_set_u64(dev, VHOST_USER_SET_PROTOCOL_FEATURES, features); > >>> + return vhost_user_set_u64(dev, VHOST_USER_SET_PROTOCOL_FEATURES, features, > >>> + false); > >>> } > >>> > >>> static int vhost_user_get_u64(struct vhost_dev *dev, int request, uint64_t *u64) >
On Mon, Jul 19, 2021 at 05:21:38PM +0300, Denis Plotnikov wrote: > On vhost-user-blk migration, qemu normally sends a number of commands > to enable logging if VHOST_USER_PROTOCOL_F_LOG_SHMFD is negotiated. > Qemu sends VHOST_USER_SET_FEATURES to enable buffers logging and > VHOST_USER_SET_VRING_ADDR per each started ring to enable "used ring" > data logging. > The issue is that qemu doesn't wait for reply from the vhost daemon > for these commands which may result in races between qemu expectation > of logging starting and actual login starting in vhost daemon. > > The race can appear as follows: on migration setup, qemu enables dirty page > logging by sending VHOST_USER_SET_FEATURES. The command doesn't arrive to a > vhost-user-blk daemon immediately and the daemon needs some time to turn the > logging on internally. If qemu doesn't wait for reply, after sending the > command, qemu may start migrate memory pages to a destination. At this time, > the logging may not be actually turned on in the daemon but some guest pages, > which the daemon is about to write to, may have already been transferred > without logging to the destination. Since the logging wasn't turned on, > those pages won't be transferred again as dirty. So we may end up with > corrupted data on the destination. > The same scenario is applicable for "used ring" data logging, which is > turned on with VHOST_USER_SET_VRING_ADDR command. > > To resolve this issue, this patch makes qemu wait for the commands result > explicilty if VHOST_USER_PROTOCOL_F_REPLY_ACK is negotiated and > logging is enabled. > > Signed-off-by: Denis Plotnikov <den-plotnikov@yandex-team.ru> > --- > v1 -> v2: > * send reply only when logging is enabled [mst] > > v0 -> v1: > * send reply for SET_VRING_ADDR, SET_FEATURES only [mst] > > hw/virtio/vhost-user.c | 37 ++++++++++++++++++++++++++++++++++--- > 1 file changed, 34 insertions(+), 3 deletions(-) > > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c > index ee57abe04526..133588b3961e 100644 > --- a/hw/virtio/vhost-user.c > +++ b/hw/virtio/vhost-user.c > @@ -1095,6 +1095,11 @@ static int vhost_user_set_mem_table(struct vhost_dev *dev, > return 0; > } > > +static bool log_enabled(uint64_t features) > +{ > + return !!(features & (0x1ULL << VHOST_F_LOG_ALL)); > +} > + > static int vhost_user_set_vring_addr(struct vhost_dev *dev, > struct vhost_vring_addr *addr) > { > @@ -1105,10 +1110,21 @@ static int vhost_user_set_vring_addr(struct vhost_dev *dev, > .hdr.size = sizeof(msg.payload.addr), > }; > > + bool reply_supported = virtio_has_feature(dev->protocol_features, > + VHOST_USER_PROTOCOL_F_REPLY_ACK); > + > + if (reply_supported && log_enabled(msg.hdr.flags)) { > + msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; > + } > + > if (vhost_user_write(dev, &msg, NULL, 0) < 0) { > return -1; > } > > + if (msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK) { > + return process_message_reply(dev, &msg); > + } > + > return 0; > } > OK this is good, but the problem is that we then still have a race if VHOST_USER_PROTOCOL_F_REPLY_ACK is not set. Bummer. Let's send VHOST_USER_GET_FEATURES in this case to flush out outstanding messages? > @@ -1288,7 +1304,8 @@ static int vhost_user_set_vring_call(struct vhost_dev *dev, > return vhost_set_vring_file(dev, VHOST_USER_SET_VRING_CALL, file); > } > > -static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64) > +static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64, > + bool need_reply) > { > VhostUserMsg msg = { > .hdr.request = request, > @@ -1297,23 +1314,37 @@ static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64) > .hdr.size = sizeof(msg.payload.u64), > }; > > + if (need_reply) { > + bool reply_supported = virtio_has_feature(dev->protocol_features, > + VHOST_USER_PROTOCOL_F_REPLY_ACK); > + if (reply_supported) { > + msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; > + } > + } > + > if (vhost_user_write(dev, &msg, NULL, 0) < 0) { > return -1; > } > > + if (msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK) { > + return process_message_reply(dev, &msg); > + } > + > return 0; > } > > static int vhost_user_set_features(struct vhost_dev *dev, > uint64_t features) > { > - return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features); > + return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features, > + log_enabled(features)); > } > > static int vhost_user_set_protocol_features(struct vhost_dev *dev, > uint64_t features) > { > - return vhost_user_set_u64(dev, VHOST_USER_SET_PROTOCOL_FEATURES, features); > + return vhost_user_set_u64(dev, VHOST_USER_SET_PROTOCOL_FEATURES, features, > + false); > } > > static int vhost_user_get_u64(struct vhost_dev *dev, int request, uint64_t *u64) > -- > 2.25.1
On 03.08.2021 18:05, Michael S. Tsirkin wrote: > On Mon, Jul 19, 2021 at 05:21:38PM +0300, Denis Plotnikov wrote: >> On vhost-user-blk migration, qemu normally sends a number of commands >> to enable logging if VHOST_USER_PROTOCOL_F_LOG_SHMFD is negotiated. >> Qemu sends VHOST_USER_SET_FEATURES to enable buffers logging and >> VHOST_USER_SET_VRING_ADDR per each started ring to enable "used ring" >> data logging. >> The issue is that qemu doesn't wait for reply from the vhost daemon >> for these commands which may result in races between qemu expectation >> of logging starting and actual login starting in vhost daemon. >> >> The race can appear as follows: on migration setup, qemu enables dirty page >> logging by sending VHOST_USER_SET_FEATURES. The command doesn't arrive to a >> vhost-user-blk daemon immediately and the daemon needs some time to turn the >> logging on internally. If qemu doesn't wait for reply, after sending the >> command, qemu may start migrate memory pages to a destination. At this time, >> the logging may not be actually turned on in the daemon but some guest pages, >> which the daemon is about to write to, may have already been transferred >> without logging to the destination. Since the logging wasn't turned on, >> those pages won't be transferred again as dirty. So we may end up with >> corrupted data on the destination. >> The same scenario is applicable for "used ring" data logging, which is >> turned on with VHOST_USER_SET_VRING_ADDR command. >> >> To resolve this issue, this patch makes qemu wait for the commands result >> explicilty if VHOST_USER_PROTOCOL_F_REPLY_ACK is negotiated and >> logging is enabled. >> >> Signed-off-by: Denis Plotnikov <den-plotnikov@yandex-team.ru> >> --- >> v1 -> v2: >> * send reply only when logging is enabled [mst] >> >> v0 -> v1: >> * send reply for SET_VRING_ADDR, SET_FEATURES only [mst] >> >> hw/virtio/vhost-user.c | 37 ++++++++++++++++++++++++++++++++++--- >> 1 file changed, 34 insertions(+), 3 deletions(-) >> >> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c >> index ee57abe04526..133588b3961e 100644 >> --- a/hw/virtio/vhost-user.c >> +++ b/hw/virtio/vhost-user.c >> @@ -1095,6 +1095,11 @@ static int vhost_user_set_mem_table(struct vhost_dev *dev, >> return 0; >> } >> >> +static bool log_enabled(uint64_t features) >> +{ >> + return !!(features & (0x1ULL << VHOST_F_LOG_ALL)); >> +} >> + >> static int vhost_user_set_vring_addr(struct vhost_dev *dev, >> struct vhost_vring_addr *addr) >> { >> @@ -1105,10 +1110,21 @@ static int vhost_user_set_vring_addr(struct vhost_dev *dev, >> .hdr.size = sizeof(msg.payload.addr), >> }; >> >> + bool reply_supported = virtio_has_feature(dev->protocol_features, >> + VHOST_USER_PROTOCOL_F_REPLY_ACK); >> + >> + if (reply_supported && log_enabled(msg.hdr.flags)) { >> + msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; >> + } >> + >> if (vhost_user_write(dev, &msg, NULL, 0) < 0) { >> return -1; >> } >> >> + if (msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK) { >> + return process_message_reply(dev, &msg); >> + } >> + >> return 0; >> } >> > OK this is good, but the problem is that we then still have a race > if VHOST_USER_PROTOCOL_F_REPLY_ACK is not set. Bummer. > > Let's send VHOST_USER_GET_FEATURES in this case to flush out outstanding > messages? Ok, I've already sent v3 with related changes. > >> @@ -1288,7 +1304,8 @@ static int vhost_user_set_vring_call(struct vhost_dev *dev, >> return vhost_set_vring_file(dev, VHOST_USER_SET_VRING_CALL, file); >> } >> >> -static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64) >> +static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64, >> + bool need_reply) >> { >> VhostUserMsg msg = { >> .hdr.request = request, >> @@ -1297,23 +1314,37 @@ static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64) >> .hdr.size = sizeof(msg.payload.u64), >> }; >> >> + if (need_reply) { >> + bool reply_supported = virtio_has_feature(dev->protocol_features, >> + VHOST_USER_PROTOCOL_F_REPLY_ACK); >> + if (reply_supported) { >> + msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; >> + } >> + } >> + >> if (vhost_user_write(dev, &msg, NULL, 0) < 0) { >> return -1; >> } >> >> + if (msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK) { >> + return process_message_reply(dev, &msg); >> + } >> + >> return 0; >> } >> >> static int vhost_user_set_features(struct vhost_dev *dev, >> uint64_t features) >> { >> - return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features); >> + return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features, >> + log_enabled(features)); >> } >> >> static int vhost_user_set_protocol_features(struct vhost_dev *dev, >> uint64_t features) >> { >> - return vhost_user_set_u64(dev, VHOST_USER_SET_PROTOCOL_FEATURES, features); >> + return vhost_user_set_u64(dev, VHOST_USER_SET_PROTOCOL_FEATURES, features, >> + false); >> } >> >> static int vhost_user_get_u64(struct vhost_dev *dev, int request, uint64_t *u64) >> -- >> 2.25.1
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c index ee57abe04526..133588b3961e 100644 --- a/hw/virtio/vhost-user.c +++ b/hw/virtio/vhost-user.c @@ -1095,6 +1095,11 @@ static int vhost_user_set_mem_table(struct vhost_dev *dev, return 0; } +static bool log_enabled(uint64_t features) +{ + return !!(features & (0x1ULL << VHOST_F_LOG_ALL)); +} + static int vhost_user_set_vring_addr(struct vhost_dev *dev, struct vhost_vring_addr *addr) { @@ -1105,10 +1110,21 @@ static int vhost_user_set_vring_addr(struct vhost_dev *dev, .hdr.size = sizeof(msg.payload.addr), }; + bool reply_supported = virtio_has_feature(dev->protocol_features, + VHOST_USER_PROTOCOL_F_REPLY_ACK); + + if (reply_supported && log_enabled(msg.hdr.flags)) { + msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; + } + if (vhost_user_write(dev, &msg, NULL, 0) < 0) { return -1; } + if (msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK) { + return process_message_reply(dev, &msg); + } + return 0; } @@ -1288,7 +1304,8 @@ static int vhost_user_set_vring_call(struct vhost_dev *dev, return vhost_set_vring_file(dev, VHOST_USER_SET_VRING_CALL, file); } -static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64) +static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64, + bool need_reply) { VhostUserMsg msg = { .hdr.request = request, @@ -1297,23 +1314,37 @@ static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64) .hdr.size = sizeof(msg.payload.u64), }; + if (need_reply) { + bool reply_supported = virtio_has_feature(dev->protocol_features, + VHOST_USER_PROTOCOL_F_REPLY_ACK); + if (reply_supported) { + msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK; + } + } + if (vhost_user_write(dev, &msg, NULL, 0) < 0) { return -1; } + if (msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK) { + return process_message_reply(dev, &msg); + } + return 0; } static int vhost_user_set_features(struct vhost_dev *dev, uint64_t features) { - return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features); + return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES, features, + log_enabled(features)); } static int vhost_user_set_protocol_features(struct vhost_dev *dev, uint64_t features) { - return vhost_user_set_u64(dev, VHOST_USER_SET_PROTOCOL_FEATURES, features); + return vhost_user_set_u64(dev, VHOST_USER_SET_PROTOCOL_FEATURES, features, + false); } static int vhost_user_get_u64(struct vhost_dev *dev, int request, uint64_t *u64)
On vhost-user-blk migration, qemu normally sends a number of commands to enable logging if VHOST_USER_PROTOCOL_F_LOG_SHMFD is negotiated. Qemu sends VHOST_USER_SET_FEATURES to enable buffers logging and VHOST_USER_SET_VRING_ADDR per each started ring to enable "used ring" data logging. The issue is that qemu doesn't wait for reply from the vhost daemon for these commands which may result in races between qemu expectation of logging starting and actual login starting in vhost daemon. The race can appear as follows: on migration setup, qemu enables dirty page logging by sending VHOST_USER_SET_FEATURES. The command doesn't arrive to a vhost-user-blk daemon immediately and the daemon needs some time to turn the logging on internally. If qemu doesn't wait for reply, after sending the command, qemu may start migrate memory pages to a destination. At this time, the logging may not be actually turned on in the daemon but some guest pages, which the daemon is about to write to, may have already been transferred without logging to the destination. Since the logging wasn't turned on, those pages won't be transferred again as dirty. So we may end up with corrupted data on the destination. The same scenario is applicable for "used ring" data logging, which is turned on with VHOST_USER_SET_VRING_ADDR command. To resolve this issue, this patch makes qemu wait for the commands result explicilty if VHOST_USER_PROTOCOL_F_REPLY_ACK is negotiated and logging is enabled. Signed-off-by: Denis Plotnikov <den-plotnikov@yandex-team.ru> --- v1 -> v2: * send reply only when logging is enabled [mst] v0 -> v1: * send reply for SET_VRING_ADDR, SET_FEATURES only [mst] hw/virtio/vhost-user.c | 37 ++++++++++++++++++++++++++++++++++--- 1 file changed, 34 insertions(+), 3 deletions(-)