| Message ID | 20191226043649.14481-2-yuri.benditovich@daynix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] virtio: reset region cache when on queue deletion | expand |
On 2019/12/26 下午12:36, Yuri Benditovich wrote: > https://bugzilla.redhat.com/show_bug.cgi?id=1708480 > Fix leak of region reference that prevents complete > device deletion on hot unplug. More information is needed here, the bug said only q35 can meet this issue. What makes q35 different here? > > Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com> > --- > hw/virtio/virtio.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > index 04716b5f6c..baadec8abc 100644 > --- a/hw/virtio/virtio.c > +++ b/hw/virtio/virtio.c > @@ -2340,6 +2340,11 @@ void virtio_del_queue(VirtIODevice *vdev, int n) > vdev->vq[n].vring.num_default = 0; > vdev->vq[n].handle_output = NULL; > vdev->vq[n].handle_aio_output = NULL; > + /* > + * with vring.num = 0 the queue will be ignored > + * in later loops of region cache reset > + */ I can't get the meaning of this comment. Thanks > + virtio_virtqueue_reset_region_cache(&vdev->vq[n]); > g_free(vdev->vq[n].used_elems); > } >
On Thu, Dec 26, 2019 at 10:58 AM Jason Wang <jasowang@redhat.com> wrote: > > > On 2019/12/26 下午12:36, Yuri Benditovich wrote: > > https://bugzilla.redhat.com/show_bug.cgi?id=1708480 > > Fix leak of region reference that prevents complete > > device deletion on hot unplug. > > > More information is needed here, the bug said only q35 can meet this > issue. What makes q35 different here? > I do not have any ready answer, I did not dig into it too much. Probably Michael Tsirkin or Paolo Bonzini can answer without digging. > > > > > Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com> > > --- > > hw/virtio/virtio.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > > index 04716b5f6c..baadec8abc 100644 > > --- a/hw/virtio/virtio.c > > +++ b/hw/virtio/virtio.c > > @@ -2340,6 +2340,11 @@ void virtio_del_queue(VirtIODevice *vdev, int n) > > vdev->vq[n].vring.num_default = 0; > > vdev->vq[n].handle_output = NULL; > > vdev->vq[n].handle_aio_output = NULL; > > + /* > > + * with vring.num = 0 the queue will be ignored > > + * in later loops of region cache reset > > + */ > > > I can't get the meaning of this comment. > > Thanks > > > > + virtio_virtqueue_reset_region_cache(&vdev->vq[n]); > > g_free(vdev->vq[n].used_elems); > > } > > >
On Thu, Dec 26, 2019 at 11:29:50AM +0200, Yuri Benditovich wrote: > On Thu, Dec 26, 2019 at 10:58 AM Jason Wang <jasowang@redhat.com> wrote: > > > > > > On 2019/12/26 下午12:36, Yuri Benditovich wrote: > > > https://bugzilla.redhat.com/show_bug.cgi?id=1708480 > > > Fix leak of region reference that prevents complete > > > device deletion on hot unplug. > > > > > > More information is needed here, the bug said only q35 can meet this > > issue. What makes q35 different here? > > > > I do not have any ready answer, I did not dig into it too much. > Probably Michael Tsirkin or Paolo Bonzini can answer without digging. > > > > > > > > Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com> > > > --- > > > hw/virtio/virtio.c | 5 +++++ > > > 1 file changed, 5 insertions(+) > > > > > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > > > index 04716b5f6c..baadec8abc 100644 > > > --- a/hw/virtio/virtio.c > > > +++ b/hw/virtio/virtio.c > > > @@ -2340,6 +2340,11 @@ void virtio_del_queue(VirtIODevice *vdev, int n) > > > vdev->vq[n].vring.num_default = 0; > > > vdev->vq[n].handle_output = NULL; > > > vdev->vq[n].handle_aio_output = NULL; > > > + /* > > > + * with vring.num = 0 the queue will be ignored > > > + * in later loops of region cache reset > > > + */ > > > > > > I can't get the meaning of this comment. > > > > Thanks > > > > > > > + virtio_virtqueue_reset_region_cache(&vdev->vq[n]); Do we need to drop this from virtio_device_free_virtqueues then? > > > g_free(vdev->vq[n].used_elems); > > > } > > > > >
On Thu, Jan 2, 2020 at 1:50 AM Michael S. Tsirkin <mst@redhat.com> wrote: > On Thu, Dec 26, 2019 at 11:29:50AM +0200, Yuri Benditovich wrote: > > On Thu, Dec 26, 2019 at 10:58 AM Jason Wang <jasowang@redhat.com> wrote: > > > > > > > > > On 2019/12/26 下午12:36, Yuri Benditovich wrote: > > > > https://bugzilla.redhat.com/show_bug.cgi?id=1708480 > > > > Fix leak of region reference that prevents complete > > > > device deletion on hot unplug. > > > > > > > > > More information is needed here, the bug said only q35 can meet this > > > issue. What makes q35 different here? > > > > > > > I do not have any ready answer, I did not dig into it too much. > > Probably Michael Tsirkin or Paolo Bonzini can answer without digging. > > > > > > > > > > > > > > Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com> > > > > --- > > > > hw/virtio/virtio.c | 5 +++++ > > > > 1 file changed, 5 insertions(+) > > > > > > > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > > > > index 04716b5f6c..baadec8abc 100644 > > > > --- a/hw/virtio/virtio.c > > > > +++ b/hw/virtio/virtio.c > > > > @@ -2340,6 +2340,11 @@ void virtio_del_queue(VirtIODevice *vdev, int > n) > > > > vdev->vq[n].vring.num_default = 0; > > > > vdev->vq[n].handle_output = NULL; > > > > vdev->vq[n].handle_aio_output = NULL; > > > > + /* > > > > + * with vring.num = 0 the queue will be ignored > > > > + * in later loops of region cache reset > > > > + */ > > > > > > > > > I can't get the meaning of this comment. > > > > > > Thanks > > > > > > > > > > + virtio_virtqueue_reset_region_cache(&vdev->vq[n]); > > > Do we need to drop this from virtio_device_free_virtqueues then? > > Not mandatory. Repetitive virtio_virtqueue_reset_region_cache does not do anything bad. Some of virtio devices do not do 'virtio_del_queue' at all. Currently virtio_device_free_virtqueues resets region cache for them. IMO, not calling 'virtio_del_queue' is a bug, but not in the scope of current series, I'll take care of that later. > > > > g_free(vdev->vq[n].used_elems); > > > > } > > > > > > > > >
On Thu, Jan 02, 2020 at 09:09:04AM +0200, Yuri Benditovich wrote: > > > On Thu, Jan 2, 2020 at 1:50 AM Michael S. Tsirkin <mst@redhat.com> wrote: > > On Thu, Dec 26, 2019 at 11:29:50AM +0200, Yuri Benditovich wrote: > > On Thu, Dec 26, 2019 at 10:58 AM Jason Wang <jasowang@redhat.com> wrote: > > > > > > > > > On 2019/12/26 下午12:36, Yuri Benditovich wrote: > > > > https://bugzilla.redhat.com/show_bug.cgi?id=1708480 > > > > Fix leak of region reference that prevents complete > > > > device deletion on hot unplug. > > > > > > > > > More information is needed here, the bug said only q35 can meet this > > > issue. What makes q35 different here? > > > > > > > I do not have any ready answer, I did not dig into it too much. > > Probably Michael Tsirkin or Paolo Bonzini can answer without digging. > > > > > > > > > > > > > > Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com> > > > > --- > > > > hw/virtio/virtio.c | 5 +++++ > > > > 1 file changed, 5 insertions(+) > > > > > > > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > > > > index 04716b5f6c..baadec8abc 100644 > > > > --- a/hw/virtio/virtio.c > > > > +++ b/hw/virtio/virtio.c > > > > @@ -2340,6 +2340,11 @@ void virtio_del_queue(VirtIODevice *vdev, int > n) > > > > vdev->vq[n].vring.num_default = 0; > > > > vdev->vq[n].handle_output = NULL; > > > > vdev->vq[n].handle_aio_output = NULL; > > > > + /* > > > > + * with vring.num = 0 the queue will be ignored > > > > + * in later loops of region cache reset > > > > + */ > > > > > > > > > I can't get the meaning of this comment. > > > > > > Thanks > > > > > > > > > > + virtio_virtqueue_reset_region_cache(&vdev->vq[n]); > > > Do we need to drop this from virtio_device_free_virtqueues then? > > > > Not mandatory. Repetitive virtio_virtqueue_reset_region_cache does not do > anything bad. > Some of virtio devices do not do 'virtio_del_queue' at all. Currently > virtio_device_free_virtqueues resets region cache for them. > IMO, not calling 'virtio_del_queue' is a bug, but not in the scope of current > series, I'll take care of that later. Maybe we should just del all queues in virtio_device_unrealize? Will allow us to drop some logic tracking which vqs were created. > > > > > g_free(vdev->vq[n].used_elems); > > > > } > > > > > > > > >
On Thu, Dec 26, 2019 at 06:36:48AM +0200, Yuri Benditovich wrote: > https://bugzilla.redhat.com/show_bug.cgi?id=1708480 > Fix leak of region reference that prevents complete > device deletion on hot unplug. > > Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com> I rebased this on top of my tree. Got this: commit f3dee6a062c1f4445768296ee39070bab9863372 Author: Yuri Benditovich <yuri.benditovich@daynix.com> Date: Thu Dec 26 06:36:48 2019 +0200 virtio: reset region cache when on queue deletion https://bugzilla.redhat.com/show_bug.cgi?id=1708480 Fix leak of region reference that prevents complete device deletion on hot unplug. Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com> Message-Id: <20191226043649.14481-2-yuri.benditovich@daynix.com> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 95d8ff8508..7b861e0ca0 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -2344,6 +2344,7 @@ void virtio_delete_queue(VirtQueue *vq) vq->handle_aio_output = NULL; g_free(vq->used_elems); vq->used_elems = NULL; + virtio_virtqueue_reset_region_cache(vq); } void virtio_del_queue(VirtIODevice *vdev, int n) Can you confirm pls?
On Sun, Jan 5, 2020 at 2:22 PM Michael S. Tsirkin <mst@redhat.com> wrote: > On Thu, Dec 26, 2019 at 06:36:48AM +0200, Yuri Benditovich wrote: > > https://bugzilla.redhat.com/show_bug.cgi?id=1708480 > > Fix leak of region reference that prevents complete > > device deletion on hot unplug. > > > > Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com> > > I rebased this on top of my tree. > > Got this: > > > commit f3dee6a062c1f4445768296ee39070bab9863372 > Author: Yuri Benditovich <yuri.benditovich@daynix.com> > Date: Thu Dec 26 06:36:48 2019 +0200 > > virtio: reset region cache when on queue deletion > > https://bugzilla.redhat.com/show_bug.cgi?id=1708480 > Fix leak of region reference that prevents complete > device deletion on hot unplug. > > Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com> > Message-Id: <20191226043649.14481-2-yuri.benditovich@daynix.com> > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > index 95d8ff8508..7b861e0ca0 100644 > --- a/hw/virtio/virtio.c > +++ b/hw/virtio/virtio.c > @@ -2344,6 +2344,7 @@ void virtio_delete_queue(VirtQueue *vq) > vq->handle_aio_output = NULL; > g_free(vq->used_elems); > vq->used_elems = NULL; > + virtio_virtqueue_reset_region_cache(vq); > } > > void virtio_del_queue(VirtIODevice *vdev, int n) > > Can you confirm pls? > Yes, it is
On Sun, Jan 5, 2020 at 1:39 PM Michael S. Tsirkin <mst@redhat.com> wrote: > On Thu, Jan 02, 2020 at 09:09:04AM +0200, Yuri Benditovich wrote: > > > > > > On Thu, Jan 2, 2020 at 1:50 AM Michael S. Tsirkin <mst@redhat.com> > wrote: > > > > On Thu, Dec 26, 2019 at 11:29:50AM +0200, Yuri Benditovich wrote: > > > On Thu, Dec 26, 2019 at 10:58 AM Jason Wang <jasowang@redhat.com> > wrote: > > > > > > > > > > > > On 2019/12/26 下午12:36, Yuri Benditovich wrote: > > > > > https://bugzilla.redhat.com/show_bug.cgi?id=1708480 > > > > > Fix leak of region reference that prevents complete > > > > > device deletion on hot unplug. > > > > > > > > > > > > More information is needed here, the bug said only q35 can meet > this > > > > issue. What makes q35 different here? > > > > > > > > > > I do not have any ready answer, I did not dig into it too much. > > > Probably Michael Tsirkin or Paolo Bonzini can answer without > digging. > > > > > > > > > > > > > > > > > > > > Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com> > > > > > --- > > > > > hw/virtio/virtio.c | 5 +++++ > > > > > 1 file changed, 5 insertions(+) > > > > > > > > > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > > > > > index 04716b5f6c..baadec8abc 100644 > > > > > --- a/hw/virtio/virtio.c > > > > > +++ b/hw/virtio/virtio.c > > > > > @@ -2340,6 +2340,11 @@ void virtio_del_queue(VirtIODevice > *vdev, int > > n) > > > > > vdev->vq[n].vring.num_default = 0; > > > > > vdev->vq[n].handle_output = NULL; > > > > > vdev->vq[n].handle_aio_output = NULL; > > > > > + /* > > > > > + * with vring.num = 0 the queue will be ignored > > > > > + * in later loops of region cache reset > > > > > + */ > > > > > > > > > > > > I can't get the meaning of this comment. > > > > > > > > Thanks > > > > > > > > > > > > > + virtio_virtqueue_reset_region_cache(&vdev->vq[n]); > > > > > > Do we need to drop this from virtio_device_free_virtqueues then? > > > > > > > > Not mandatory. Repetitive virtio_virtqueue_reset_region_cache does not > do > > anything bad. > > Some of virtio devices do not do 'virtio_del_queue' at all. Currently > > virtio_device_free_virtqueues resets region cache for them. > > IMO, not calling 'virtio_del_queue' is a bug, but not in the scope of > current > > series, I'll take care of that later. > > Maybe we should just del all queues in virtio_device_unrealize? > Will allow us to drop some logic tracking which vqs were created. > > Yes, this is also possible with some rework of virtio_device_free_virtqueues. virtio-net has some additional operations around queue deletion, it deletes queues when switches from single queue to multiple. > > > > > > > > g_free(vdev->vq[n].used_elems); > > > > > } > > > > > > > > > > > > > > >
Michael, Can you please comment on Jason's question: why we have a problem only with q35 and not with legacy pc? If you have a simple answer, it will help us in further work with other hot plug/unplug problems. Thanks, Yuri Benditovich On Sun, Jan 5, 2020 at 6:21 PM Yuri Benditovich <yuri.benditovich@daynix.com> wrote: > > > On Sun, Jan 5, 2020 at 1:39 PM Michael S. Tsirkin <mst@redhat.com> wrote: > >> On Thu, Jan 02, 2020 at 09:09:04AM +0200, Yuri Benditovich wrote: >> > >> > >> > On Thu, Jan 2, 2020 at 1:50 AM Michael S. Tsirkin <mst@redhat.com> >> wrote: >> > >> > On Thu, Dec 26, 2019 at 11:29:50AM +0200, Yuri Benditovich wrote: >> > > On Thu, Dec 26, 2019 at 10:58 AM Jason Wang <jasowang@redhat.com> >> wrote: >> > > > >> > > > >> > > > On 2019/12/26 下午12:36, Yuri Benditovich wrote: >> > > > > https://bugzilla.redhat.com/show_bug.cgi?id=1708480 >> > > > > Fix leak of region reference that prevents complete >> > > > > device deletion on hot unplug. >> > > > >> > > > >> > > > More information is needed here, the bug said only q35 can meet >> this >> > > > issue. What makes q35 different here? >> > > > >> > > >> > > I do not have any ready answer, I did not dig into it too much. >> > > Probably Michael Tsirkin or Paolo Bonzini can answer without >> digging. >> > >> > >> > >> > > > >> > > > > >> > > > > Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com> >> > > > > --- >> > > > > hw/virtio/virtio.c | 5 +++++ >> > > > > 1 file changed, 5 insertions(+) >> > > > > >> > > > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c >> > > > > index 04716b5f6c..baadec8abc 100644 >> > > > > --- a/hw/virtio/virtio.c >> > > > > +++ b/hw/virtio/virtio.c >> > > > > @@ -2340,6 +2340,11 @@ void virtio_del_queue(VirtIODevice >> *vdev, int >> > n) >> > > > > vdev->vq[n].vring.num_default = 0; >> > > > > vdev->vq[n].handle_output = NULL; >> > > > > vdev->vq[n].handle_aio_output = NULL; >> > > > > + /* >> > > > > + * with vring.num = 0 the queue will be ignored >> > > > > + * in later loops of region cache reset >> > > > > + */ >> > > > >> > > > >> > > > I can't get the meaning of this comment. >> > > > >> > > > Thanks >> > > > >> > > > >> > > > > + virtio_virtqueue_reset_region_cache(&vdev->vq[n]); >> > >> > >> > Do we need to drop this from virtio_device_free_virtqueues then? >> > >> > >> > >> > Not mandatory. Repetitive virtio_virtqueue_reset_region_cache does not >> do >> > anything bad. >> > Some of virtio devices do not do 'virtio_del_queue' at all. Currently >> > virtio_device_free_virtqueues resets region cache for them. >> > IMO, not calling 'virtio_del_queue' is a bug, but not in the scope of >> current >> > series, I'll take care of that later. >> >> Maybe we should just del all queues in virtio_device_unrealize? >> Will allow us to drop some logic tracking which vqs were created. >> >> > Yes, this is also possible with some rework of > virtio_device_free_virtqueues. > virtio-net has some additional operations around queue deletion, it > deletes queues when switches from single queue to multiple. > > >> >> > >> > > > > g_free(vdev->vq[n].used_elems); >> > > > > } >> > > > > >> > > > >> > >> > >> >>
I guess it somehow has to do with the following:
if (proxy->disable_legacy == ON_OFF_AUTO_AUTO) {
proxy->disable_legacy = pcie_port ? ON_OFF_AUTO_ON : ON_OFF_AUTO_OFF;
}
so by default device on an express port does not have a legacy interface.
Somehow having a legacy interface fixes things?
Does enabling legacy on q35 without this patch fix things?
And does disabling legacy on PIIX without this patch break thing?
How can having a legacy interface fix things if it's not
even active? I don't know. Is there a chance windows drivers use the
legacy interface on a transitional device by mistake?
On Mon, Jan 06, 2020 at 11:10:18AM +0200, Yuri Benditovich wrote:
> Michael,
> Can you please comment on Jason's question: why we have a problem only with q35
> and not with legacy pc?
> If you have a simple answer, it will help us in further work with other hot
> plug/unplug problems.
>
> Thanks,
> Yuri Benditovich
>
> On Sun, Jan 5, 2020 at 6:21 PM Yuri Benditovich <yuri.benditovich@daynix.com>
> wrote:
>
>
>
> On Sun, Jan 5, 2020 at 1:39 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Thu, Jan 02, 2020 at 09:09:04AM +0200, Yuri Benditovich wrote:
> >
> >
> > On Thu, Jan 2, 2020 at 1:50 AM Michael S. Tsirkin <mst@redhat.com>
> wrote:
> >
> > On Thu, Dec 26, 2019 at 11:29:50AM +0200, Yuri Benditovich wrote:
> > > On Thu, Dec 26, 2019 at 10:58 AM Jason Wang <
> jasowang@redhat.com> wrote:
> > > >
> > > >
> > > > On 2019/12/26 下午12:36, Yuri Benditovich wrote:
> > > > > https://bugzilla.redhat.com/show_bug.cgi?id=1708480
> > > > > Fix leak of region reference that prevents complete
> > > > > device deletion on hot unplug.
> > > >
> > > >
> > > > More information is needed here, the bug said only q35 can
> meet this
> > > > issue. What makes q35 different here?
> > > >
> > >
> > > I do not have any ready answer, I did not dig into it too much.
> > > Probably Michael Tsirkin or Paolo Bonzini can answer without
> digging.
> >
> >
> >
> > > >
> > > > >
> > > > > Signed-off-by: Yuri Benditovich <
> yuri.benditovich@daynix.com>
> > > > > ---
> > > > > hw/virtio/virtio.c | 5 +++++
> > > > > 1 file changed, 5 insertions(+)
> > > > >
> > > > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> > > > > index 04716b5f6c..baadec8abc 100644
> > > > > --- a/hw/virtio/virtio.c
> > > > > +++ b/hw/virtio/virtio.c
> > > > > @@ -2340,6 +2340,11 @@ void virtio_del_queue(VirtIODevice
> *vdev, int
> > n)
> > > > > vdev->vq[n].vring.num_default = 0;
> > > > > vdev->vq[n].handle_output = NULL;
> > > > > vdev->vq[n].handle_aio_output = NULL;
> > > > > + /*
> > > > > + * with vring.num = 0 the queue will be ignored
> > > > > + * in later loops of region cache reset
> > > > > + */
> > > >
> > > >
> > > > I can't get the meaning of this comment.
> > > >
> > > > Thanks
> > > >
> > > >
> > > > > + virtio_virtqueue_reset_region_cache(&vdev->vq[n]);
> >
> >
> > Do we need to drop this from virtio_device_free_virtqueues then?
> >
> >
> >
> > Not mandatory. Repetitive virtio_virtqueue_reset_region_cache does
> not do
> > anything bad.
> > Some of virtio devices do not do 'virtio_del_queue' at all.
> Currently
> > virtio_device_free_virtqueues resets region cache for them.
> > IMO, not calling 'virtio_del_queue' is a bug, but not in the scope of
> current
> > series, I'll take care of that later.
>
> Maybe we should just del all queues in virtio_device_unrealize?
> Will allow us to drop some logic tracking which vqs were created.
>
>
>
> Yes, this is also possible with some rework of
> virtio_device_free_virtqueues.
> virtio-net has some additional operations around queue deletion, it deletes
> queues when switches from single queue to multiple.
>
>
>
> >
> > > > > g_free(vdev->vq[n].used_elems);
> > > > > }
> > > > >
> > > >
> >
> >
>
>
On Mon, Jan 6, 2020 at 11:58 AM Michael S. Tsirkin <mst@redhat.com> wrote: > I guess it somehow has to do with the following: > > if (proxy->disable_legacy == ON_OFF_AUTO_AUTO) { > proxy->disable_legacy = pcie_port ? ON_OFF_AUTO_ON : > ON_OFF_AUTO_OFF; > } > > so by default device on an express port does not have a legacy interface. > > Somehow having a legacy interface fixes things? > I'll check it. > Does enabling legacy on q35 without this patch fix things? > I'll check it also. > And does disabling legacy on PIIX without this patch break thing? > I'll check it also. > > How can having a legacy interface fix things if it's not > even active? I don't know. Is there a chance windows drivers use the > legacy interface on a transitional device by mistake? > > I'll recheck it. I do not think we use legacy interface on modern device even if it has one. > > On Mon, Jan 06, 2020 at 11:10:18AM +0200, Yuri Benditovich wrote: > > Michael, > > Can you please comment on Jason's question: why we have a problem only > with q35 > > and not with legacy pc? > > If you have a simple answer, it will help us in further work with other > hot > > plug/unplug problems. > > > > Thanks, > > Yuri Benditovich > > > > On Sun, Jan 5, 2020 at 6:21 PM Yuri Benditovich < > yuri.benditovich@daynix.com> > > wrote: > > > > > > > > On Sun, Jan 5, 2020 at 1:39 PM Michael S. Tsirkin <mst@redhat.com> > wrote: > > > > On Thu, Jan 02, 2020 at 09:09:04AM +0200, Yuri Benditovich wrote: > > > > > > > > > On Thu, Jan 2, 2020 at 1:50 AM Michael S. Tsirkin < > mst@redhat.com> > > wrote: > > > > > > On Thu, Dec 26, 2019 at 11:29:50AM +0200, Yuri Benditovich > wrote: > > > > On Thu, Dec 26, 2019 at 10:58 AM Jason Wang < > > jasowang@redhat.com> wrote: > > > > > > > > > > > > > > > On 2019/12/26 下午12:36, Yuri Benditovich wrote: > > > > > > https://bugzilla.redhat.com/show_bug.cgi?id=1708480 > > > > > > Fix leak of region reference that prevents complete > > > > > > device deletion on hot unplug. > > > > > > > > > > > > > > > More information is needed here, the bug said only q35 > can > > meet this > > > > > issue. What makes q35 different here? > > > > > > > > > > > > > I do not have any ready answer, I did not dig into it > too much. > > > > Probably Michael Tsirkin or Paolo Bonzini can answer > without > > digging. > > > > > > > > > > > > > > > > > > > > > > > > > > Signed-off-by: Yuri Benditovich < > > yuri.benditovich@daynix.com> > > > > > > --- > > > > > > hw/virtio/virtio.c | 5 +++++ > > > > > > 1 file changed, 5 insertions(+) > > > > > > > > > > > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > > > > > > index 04716b5f6c..baadec8abc 100644 > > > > > > --- a/hw/virtio/virtio.c > > > > > > +++ b/hw/virtio/virtio.c > > > > > > @@ -2340,6 +2340,11 @@ void > virtio_del_queue(VirtIODevice > > *vdev, int > > > n) > > > > > > vdev->vq[n].vring.num_default = 0; > > > > > > vdev->vq[n].handle_output = NULL; > > > > > > vdev->vq[n].handle_aio_output = NULL; > > > > > > + /* > > > > > > + * with vring.num = 0 the queue will be ignored > > > > > > + * in later loops of region cache reset > > > > > > + */ > > > > > > > > > > > > > > > I can't get the meaning of this comment. > > > > > > > > > > Thanks > > > > > > > > > > > > > > > > + > virtio_virtqueue_reset_region_cache(&vdev->vq[n]); > > > > > > > > > Do we need to drop this from virtio_device_free_virtqueues > then? > > > > > > > > > > > > Not mandatory. Repetitive > virtio_virtqueue_reset_region_cache does > > not do > > > anything bad. > > > Some of virtio devices do not do 'virtio_del_queue' at all. > > Currently > > > virtio_device_free_virtqueues resets region cache for them. > > > IMO, not calling 'virtio_del_queue' is a bug, but not in the > scope of > > current > > > series, I'll take care of that later. > > > > Maybe we should just del all queues in virtio_device_unrealize? > > Will allow us to drop some logic tracking which vqs were created. > > > > > > > > Yes, this is also possible with some rework of > > virtio_device_free_virtqueues. > > virtio-net has some additional operations around queue deletion, it > deletes > > queues when switches from single queue to multiple. > > > > > > > > > > > > > > > g_free(vdev->vq[n].used_elems); > > > > > > } > > > > > > > > > > > > > > > > > > > > > > >
On Mon, Jan 6, 2020 at 12:37 PM Yuri Benditovich < yuri.benditovich@daynix.com> wrote: > > On Mon, Jan 6, 2020 at 11:58 AM Michael S. Tsirkin <mst@redhat.com> wrote: > >> I guess it somehow has to do with the following: >> >> if (proxy->disable_legacy == ON_OFF_AUTO_AUTO) { >> proxy->disable_legacy = pcie_port ? ON_OFF_AUTO_ON : >> ON_OFF_AUTO_OFF; >> } >> >> so by default device on an express port does not have a legacy interface. >> >> Somehow having a legacy interface fixes things? >> > > No, transitional virtio-net on q35 behaves exactly as the modern one. > > >> Does enabling legacy on q35 without this patch fix things? >> > > No, legacy virtio-net on q35 has the same problem. There is also an additional problem with legacy device unplug on q35, but I think it is not in the scope of this discussion. > > >> And does disabling legacy on PIIX without this patch break thing? >> > > No, modern device on PIIX does hot unplug without problems. > > >> >> How can having a legacy interface fix things if it's not >> even active? I don't know. Is there a chance windows drivers use the >> legacy interface on a transitional device by mistake? >> > As far as I can see - no. The driver works with the device depending on VERSION_1 > I'll recheck it. I do not think we use legacy interface on modern device > even if it has one. > > >> >> On Mon, Jan 06, 2020 at 11:10:18AM +0200, Yuri Benditovich wrote: >> > Michael, >> > Can you please comment on Jason's question: why we have a problem only >> with q35 >> > and not with legacy pc? >> > If you have a simple answer, it will help us in further work with other >> hot >> > plug/unplug problems. >> > >> > Thanks, >> > Yuri Benditovich >> > >> > On Sun, Jan 5, 2020 at 6:21 PM Yuri Benditovich < >> yuri.benditovich@daynix.com> >> > wrote: >> > >> > >> > >> > On Sun, Jan 5, 2020 at 1:39 PM Michael S. Tsirkin <mst@redhat.com> >> wrote: >> > >> > On Thu, Jan 02, 2020 at 09:09:04AM +0200, Yuri Benditovich >> wrote: >> > > >> > > >> > > On Thu, Jan 2, 2020 at 1:50 AM Michael S. Tsirkin < >> mst@redhat.com> >> > wrote: >> > > >> > > On Thu, Dec 26, 2019 at 11:29:50AM +0200, Yuri >> Benditovich wrote: >> > > > On Thu, Dec 26, 2019 at 10:58 AM Jason Wang < >> > jasowang@redhat.com> wrote: >> > > > > >> > > > > >> > > > > On 2019/12/26 下午12:36, Yuri Benditovich wrote: >> > > > > > https://bugzilla.redhat.com/show_bug.cgi?id=1708480 >> > > > > > Fix leak of region reference that prevents complete >> > > > > > device deletion on hot unplug. >> > > > > >> > > > > >> > > > > More information is needed here, the bug said only >> q35 can >> > meet this >> > > > > issue. What makes q35 different here? >> > > > > >> > > > >> > > > I do not have any ready answer, I did not dig into it >> too much. >> > > > Probably Michael Tsirkin or Paolo Bonzini can answer >> without >> > digging. >> > > >> > > >> > > >> > > > > >> > > > > > >> > > > > > Signed-off-by: Yuri Benditovich < >> > yuri.benditovich@daynix.com> >> > > > > > --- >> > > > > > hw/virtio/virtio.c | 5 +++++ >> > > > > > 1 file changed, 5 insertions(+) >> > > > > > >> > > > > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c >> > > > > > index 04716b5f6c..baadec8abc 100644 >> > > > > > --- a/hw/virtio/virtio.c >> > > > > > +++ b/hw/virtio/virtio.c >> > > > > > @@ -2340,6 +2340,11 @@ void >> virtio_del_queue(VirtIODevice >> > *vdev, int >> > > n) >> > > > > > vdev->vq[n].vring.num_default = 0; >> > > > > > vdev->vq[n].handle_output = NULL; >> > > > > > vdev->vq[n].handle_aio_output = NULL; >> > > > > > + /* >> > > > > > + * with vring.num = 0 the queue will be ignored >> > > > > > + * in later loops of region cache reset >> > > > > > + */ >> > > > > >> > > > > >> > > > > I can't get the meaning of this comment. >> > > > > >> > > > > Thanks >> > > > > >> > > > > >> > > > > > + >> virtio_virtqueue_reset_region_cache(&vdev->vq[n]); >> > > >> > > >> > > Do we need to drop this from >> virtio_device_free_virtqueues then? >> > > >> > > >> > > >> > > Not mandatory. Repetitive >> virtio_virtqueue_reset_region_cache does >> > not do >> > > anything bad. >> > > Some of virtio devices do not do 'virtio_del_queue' at all. >> > Currently >> > > virtio_device_free_virtqueues resets region cache for them. >> > > IMO, not calling 'virtio_del_queue' is a bug, but not in the >> scope of >> > current >> > > series, I'll take care of that later. >> > >> > Maybe we should just del all queues in virtio_device_unrealize? >> > Will allow us to drop some logic tracking which vqs were >> created. >> > >> > >> > >> > Yes, this is also possible with some rework of >> > virtio_device_free_virtqueues. >> > virtio-net has some additional operations around queue deletion, it >> deletes >> > queues when switches from single queue to multiple. >> > >> > >> > >> > > >> > > > > > g_free(vdev->vq[n].used_elems); >> > > > > > } >> > > > > > >> > > > > >> > > >> > > >> > >> > >> >>
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 04716b5f6c..baadec8abc 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -2340,6 +2340,11 @@ void virtio_del_queue(VirtIODevice *vdev, int n) vdev->vq[n].vring.num_default = 0; vdev->vq[n].handle_output = NULL; vdev->vq[n].handle_aio_output = NULL; + /* + * with vring.num = 0 the queue will be ignored + * in later loops of region cache reset + */ + virtio_virtqueue_reset_region_cache(&vdev->vq[n]); g_free(vdev->vq[n].used_elems); }
https://bugzilla.redhat.com/show_bug.cgi?id=1708480 Fix leak of region reference that prevents complete device deletion on hot unplug. Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com> --- hw/virtio/virtio.c | 5 +++++ 1 file changed, 5 insertions(+)