| Message ID | 20240618121958.88673-1-thuth@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | hw/virtio: Fix the de-initialization of vhost-user devices | expand |
On Tue, 18 Jun 2024 15:19, Thomas Huth <thuth@redhat.com> wrote: >The unrealize functions of the various vhost-user devices are >calling the corresponding vhost_*_set_status() functions with a >status of 0 to shut down the device correctly. > >Now these vhost_*_set_status() functions all follow this scheme: > > bool should_start = virtio_device_should_start(vdev, status); > > if (vhost_dev_is_started(&vvc->vhost_dev) == should_start) { > return; > } > > if (should_start) { > /* ... do the initialization stuff ... */ > } else { > /* ... do the cleanup stuff ... */ > } > >The problem here is virtio_device_should_start(vdev, 0) currently >always returns "true" since it internally only looks at vdev->started >instead of looking at the "status" parameter. Thus once the device >got started once, virtio_device_should_start() always returns true virtio_device_should_start() returning true if it's already started and running looks like a code smell to me... it intuitively feels like a ternary state instead of boolean: not startable, startable, already started. >and thus the vhost_*_set_status() functions return early, without >ever doing any clean-up when being called with status == 0. This >causes e.g. problems when trying to hot-plug and hot-unplug a vhost >user devices multiple times since the de-initialization step is >completely skipped during the unplug operation. > >This bug has been introduced in commit 9f6bcfd99f ("hw/virtio: move >vm_running check to virtio_device_started") which replaced > > should_start = status & VIRTIO_CONFIG_S_DRIVER_OK; > >with > > should_start = virtio_device_started(vdev, status); > >which later got replaced by virtio_device_should_start(). This blocked >the possibility to set should_start to false in case the status flag >VIRTIO_CONFIG_S_DRIVER_OK was not set. > >Fix it by adjusting the virtio_device_should_start() function to >only consider the status flag instead of vdev->started. Since this >function is only used in the various vhost_*_set_status() functions >for exactly the same purpose, it should be fine to fix it in this >central place there without any risk to change the behavior of other >code. > >Fixes: 9f6bcfd99f ("hw/virtio: move vm_running check to virtio_device_started") >Buglink: https://issues.redhat.com/browse/RHEL-40708 >Signed-off-by: Thomas Huth <thuth@redhat.com> >--- Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
On 18/06/2024 14.19, Thomas Huth wrote: > The unrealize functions of the various vhost-user devices are > calling the corresponding vhost_*_set_status() functions with a > status of 0 to shut down the device correctly. > > Now these vhost_*_set_status() functions all follow this scheme: > > bool should_start = virtio_device_should_start(vdev, status); > > if (vhost_dev_is_started(&vvc->vhost_dev) == should_start) { > return; > } > > if (should_start) { > /* ... do the initialization stuff ... */ > } else { > /* ... do the cleanup stuff ... */ > } > > The problem here is virtio_device_should_start(vdev, 0) currently > always returns "true" since it internally only looks at vdev->started > instead of looking at the "status" parameter. Thus once the device > got started once, virtio_device_should_start() always returns true > and thus the vhost_*_set_status() functions return early, without > ever doing any clean-up when being called with status == 0. This > causes e.g. problems when trying to hot-plug and hot-unplug a vhost > user devices multiple times since the de-initialization step is > completely skipped during the unplug operation. > > This bug has been introduced in commit 9f6bcfd99f ("hw/virtio: move > vm_running check to virtio_device_started") which replaced > > should_start = status & VIRTIO_CONFIG_S_DRIVER_OK; > > with > > should_start = virtio_device_started(vdev, status); > > which later got replaced by virtio_device_should_start(). This blocked > the possibility to set should_start to false in case the status flag > VIRTIO_CONFIG_S_DRIVER_OK was not set. > > Fix it by adjusting the virtio_device_should_start() function to > only consider the status flag instead of vdev->started. Since this > function is only used in the various vhost_*_set_status() functions > for exactly the same purpose, it should be fine to fix it in this > central place there without any risk to change the behavior of other > code. > > Fixes: 9f6bcfd99f ("hw/virtio: move vm_running check to virtio_device_started") > Buglink: https://issues.redhat.com/browse/RHEL-40708 > Signed-off-by: Thomas Huth <thuth@redhat.com> > --- > include/hw/virtio/virtio.h | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h > index 7d5ffdc145..2eafad17b8 100644 > --- a/include/hw/virtio/virtio.h > +++ b/include/hw/virtio/virtio.h > @@ -470,9 +470,9 @@ static inline bool virtio_device_started(VirtIODevice *vdev, uint8_t status) > * @vdev - the VirtIO device > * @status - the devices status bits > * > - * This is similar to virtio_device_started() but also encapsulates a > - * check on the VM status which would prevent a device starting > - * anyway. > + * This is similar to virtio_device_started() but ignores vdev->started > + * and also encapsulates a check on the VM status which would prevent a > + * device from starting anyway. > */ > static inline bool virtio_device_should_start(VirtIODevice *vdev, uint8_t status) > { > @@ -480,7 +480,7 @@ static inline bool virtio_device_should_start(VirtIODevice *vdev, uint8_t status > return false; > } > > - return virtio_device_started(vdev, status); > + return status & VIRTIO_CONFIG_S_DRIVER_OK; > } Michael, any concerns or comments about this patch? If not, I could also take it via my s390x tree since this fixes vhost-ccw devices on s390x. Thomas
On Mon, Jul 01, 2024 at 04:07:56PM +0200, Thomas Huth wrote: > On 18/06/2024 14.19, Thomas Huth wrote: > > The unrealize functions of the various vhost-user devices are > > calling the corresponding vhost_*_set_status() functions with a > > status of 0 to shut down the device correctly. > > > > Now these vhost_*_set_status() functions all follow this scheme: > > > > bool should_start = virtio_device_should_start(vdev, status); > > > > if (vhost_dev_is_started(&vvc->vhost_dev) == should_start) { > > return; > > } > > > > if (should_start) { > > /* ... do the initialization stuff ... */ > > } else { > > /* ... do the cleanup stuff ... */ > > } > > > > The problem here is virtio_device_should_start(vdev, 0) currently > > always returns "true" since it internally only looks at vdev->started > > instead of looking at the "status" parameter. Thus once the device > > got started once, virtio_device_should_start() always returns true > > and thus the vhost_*_set_status() functions return early, without > > ever doing any clean-up when being called with status == 0. This > > causes e.g. problems when trying to hot-plug and hot-unplug a vhost > > user devices multiple times since the de-initialization step is > > completely skipped during the unplug operation. > > > > This bug has been introduced in commit 9f6bcfd99f ("hw/virtio: move > > vm_running check to virtio_device_started") which replaced > > > > should_start = status & VIRTIO_CONFIG_S_DRIVER_OK; > > > > with > > > > should_start = virtio_device_started(vdev, status); > > > > which later got replaced by virtio_device_should_start(). This blocked > > the possibility to set should_start to false in case the status flag > > VIRTIO_CONFIG_S_DRIVER_OK was not set. > > > > Fix it by adjusting the virtio_device_should_start() function to > > only consider the status flag instead of vdev->started. Since this > > function is only used in the various vhost_*_set_status() functions > > for exactly the same purpose, it should be fine to fix it in this > > central place there without any risk to change the behavior of other > > code. > > > > Fixes: 9f6bcfd99f ("hw/virtio: move vm_running check to virtio_device_started") > > Buglink: https://issues.redhat.com/browse/RHEL-40708 > > Signed-off-by: Thomas Huth <thuth@redhat.com> > > --- > > include/hw/virtio/virtio.h | 8 ++++---- > > 1 file changed, 4 insertions(+), 4 deletions(-) > > > > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h > > index 7d5ffdc145..2eafad17b8 100644 > > --- a/include/hw/virtio/virtio.h > > +++ b/include/hw/virtio/virtio.h > > @@ -470,9 +470,9 @@ static inline bool virtio_device_started(VirtIODevice *vdev, uint8_t status) > > * @vdev - the VirtIO device > > * @status - the devices status bits > > * > > - * This is similar to virtio_device_started() but also encapsulates a > > - * check on the VM status which would prevent a device starting > > - * anyway. > > + * This is similar to virtio_device_started() but ignores vdev->started > > + * and also encapsulates a check on the VM status which would prevent a > > + * device from starting anyway. > > */ > > static inline bool virtio_device_should_start(VirtIODevice *vdev, uint8_t status) > > { > > @@ -480,7 +480,7 @@ static inline bool virtio_device_should_start(VirtIODevice *vdev, uint8_t status > > return false; > > } > > - return virtio_device_started(vdev, status); > > + return status & VIRTIO_CONFIG_S_DRIVER_OK; > > } > > Michael, any concerns or comments about this patch? > > If not, I could also take it via my s390x tree since this fixes vhost-ccw > devices on s390x. > > Thomas I'm working on a pull request with this today. I can drop it if you prefer ...
On 01/07/2024 17.06, Michael S. Tsirkin wrote: > On Mon, Jul 01, 2024 at 04:07:56PM +0200, Thomas Huth wrote: >> On 18/06/2024 14.19, Thomas Huth wrote: >>> The unrealize functions of the various vhost-user devices are >>> calling the corresponding vhost_*_set_status() functions with a >>> status of 0 to shut down the device correctly. >>> >>> Now these vhost_*_set_status() functions all follow this scheme: >>> >>> bool should_start = virtio_device_should_start(vdev, status); >>> >>> if (vhost_dev_is_started(&vvc->vhost_dev) == should_start) { >>> return; >>> } >>> >>> if (should_start) { >>> /* ... do the initialization stuff ... */ >>> } else { >>> /* ... do the cleanup stuff ... */ >>> } >>> >>> The problem here is virtio_device_should_start(vdev, 0) currently >>> always returns "true" since it internally only looks at vdev->started >>> instead of looking at the "status" parameter. Thus once the device >>> got started once, virtio_device_should_start() always returns true >>> and thus the vhost_*_set_status() functions return early, without >>> ever doing any clean-up when being called with status == 0. This >>> causes e.g. problems when trying to hot-plug and hot-unplug a vhost >>> user devices multiple times since the de-initialization step is >>> completely skipped during the unplug operation. >>> >>> This bug has been introduced in commit 9f6bcfd99f ("hw/virtio: move >>> vm_running check to virtio_device_started") which replaced >>> >>> should_start = status & VIRTIO_CONFIG_S_DRIVER_OK; >>> >>> with >>> >>> should_start = virtio_device_started(vdev, status); >>> >>> which later got replaced by virtio_device_should_start(). This blocked >>> the possibility to set should_start to false in case the status flag >>> VIRTIO_CONFIG_S_DRIVER_OK was not set. >>> >>> Fix it by adjusting the virtio_device_should_start() function to >>> only consider the status flag instead of vdev->started. Since this >>> function is only used in the various vhost_*_set_status() functions >>> for exactly the same purpose, it should be fine to fix it in this >>> central place there without any risk to change the behavior of other >>> code. >>> >>> Fixes: 9f6bcfd99f ("hw/virtio: move vm_running check to virtio_device_started") >>> Buglink: https://issues.redhat.com/browse/RHEL-40708 >>> Signed-off-by: Thomas Huth <thuth@redhat.com> >>> --- >>> include/hw/virtio/virtio.h | 8 ++++---- >>> 1 file changed, 4 insertions(+), 4 deletions(-) >>> >>> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h >>> index 7d5ffdc145..2eafad17b8 100644 >>> --- a/include/hw/virtio/virtio.h >>> +++ b/include/hw/virtio/virtio.h >>> @@ -470,9 +470,9 @@ static inline bool virtio_device_started(VirtIODevice *vdev, uint8_t status) >>> * @vdev - the VirtIO device >>> * @status - the devices status bits >>> * >>> - * This is similar to virtio_device_started() but also encapsulates a >>> - * check on the VM status which would prevent a device starting >>> - * anyway. >>> + * This is similar to virtio_device_started() but ignores vdev->started >>> + * and also encapsulates a check on the VM status which would prevent a >>> + * device from starting anyway. >>> */ >>> static inline bool virtio_device_should_start(VirtIODevice *vdev, uint8_t status) >>> { >>> @@ -480,7 +480,7 @@ static inline bool virtio_device_should_start(VirtIODevice *vdev, uint8_t status >>> return false; >>> } >>> - return virtio_device_started(vdev, status); >>> + return status & VIRTIO_CONFIG_S_DRIVER_OK; >>> } >> >> Michael, any concerns or comments about this patch? >> >> If not, I could also take it via my s390x tree since this fixes vhost-ccw >> devices on s390x. >> >> Thomas > > I'm working on a pull request with this today. > I can drop it if you prefer ... Ah, perfect, please include it in your PR then! Thanks, Thomas
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h index 7d5ffdc145..2eafad17b8 100644 --- a/include/hw/virtio/virtio.h +++ b/include/hw/virtio/virtio.h @@ -470,9 +470,9 @@ static inline bool virtio_device_started(VirtIODevice *vdev, uint8_t status) * @vdev - the VirtIO device * @status - the devices status bits * - * This is similar to virtio_device_started() but also encapsulates a - * check on the VM status which would prevent a device starting - * anyway. + * This is similar to virtio_device_started() but ignores vdev->started + * and also encapsulates a check on the VM status which would prevent a + * device from starting anyway. */ static inline bool virtio_device_should_start(VirtIODevice *vdev, uint8_t status) { @@ -480,7 +480,7 @@ static inline bool virtio_device_should_start(VirtIODevice *vdev, uint8_t status return false; } - return virtio_device_started(vdev, status); + return status & VIRTIO_CONFIG_S_DRIVER_OK; } static inline void virtio_set_started(VirtIODevice *vdev, bool started)
The unrealize functions of the various vhost-user devices are calling the corresponding vhost_*_set_status() functions with a status of 0 to shut down the device correctly. Now these vhost_*_set_status() functions all follow this scheme: bool should_start = virtio_device_should_start(vdev, status); if (vhost_dev_is_started(&vvc->vhost_dev) == should_start) { return; } if (should_start) { /* ... do the initialization stuff ... */ } else { /* ... do the cleanup stuff ... */ } The problem here is virtio_device_should_start(vdev, 0) currently always returns "true" since it internally only looks at vdev->started instead of looking at the "status" parameter. Thus once the device got started once, virtio_device_should_start() always returns true and thus the vhost_*_set_status() functions return early, without ever doing any clean-up when being called with status == 0. This causes e.g. problems when trying to hot-plug and hot-unplug a vhost user devices multiple times since the de-initialization step is completely skipped during the unplug operation. This bug has been introduced in commit 9f6bcfd99f ("hw/virtio: move vm_running check to virtio_device_started") which replaced should_start = status & VIRTIO_CONFIG_S_DRIVER_OK; with should_start = virtio_device_started(vdev, status); which later got replaced by virtio_device_should_start(). This blocked the possibility to set should_start to false in case the status flag VIRTIO_CONFIG_S_DRIVER_OK was not set. Fix it by adjusting the virtio_device_should_start() function to only consider the status flag instead of vdev->started. Since this function is only used in the various vhost_*_set_status() functions for exactly the same purpose, it should be fine to fix it in this central place there without any risk to change the behavior of other code. Fixes: 9f6bcfd99f ("hw/virtio: move vm_running check to virtio_device_started") Buglink: https://issues.redhat.com/browse/RHEL-40708 Signed-off-by: Thomas Huth <thuth@redhat.com> --- include/hw/virtio/virtio.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)