RE: [VIRTIO GPU PATCH v3 0/1] Add new feature flag VIRTIO_GPU_F_FREEZE_S3

[Parav Pandit <parav@nvidia.com>]

> From: virtio-dev@lists.oasis-open.org <virtio-dev@lists.oasis-open.org> On
> Behalf Of Chen, Jiqian
> Sent: Wednesday, August 2, 2023 8:51 AM
> Hi all,
> 
> Do you have any other comments on the modification of virtio-gpu S3?
> Looking forward to your reply and comments.
> 
I am not familiar with the GPU, so a dumb question is, why the S3 state is gpu specific?
Can a transport specific suspend state be used and apply to all virtio devices?
And can you please add both the rationale to the commit message?

> On 2023/7/20 20:18, Jiqian Chen wrote:
> > v3:
> >
> > Hi all,
> > Thanks for Gerd Hoffmann's advice. V3 makes below changes:
> > * Use enum for freeze mode, so this can be extended with more
> >   modes in the future.
> > * Rename functions and paratemers with "_S3" postfix.
> > * Explain in more detail
> >
> > And latest version on QEMU and Linux kernel side:
> > 	QEMU: https://lore.kernel.org/qemu-devel/20230720120816.8751-1-
> Jiqian.Chen@amd.com
> > 	Kernel:
> > https://lore.kernel.org/lkml/20230720115805.8206-1-Jiqian.Chen@amd.com
> > /T/#t
> >
> > Best regards,
> > Jiqian Chen.
> >
> >
> > v2:
> > link,
> > https://lists.oasis-open.org/archives/virtio-comment/202307/msg00160.h
> > tml
> >
> > Hi all,
> > Thanks to Gerd Hoffmann for his suggestions. V2 makes below changes:
> > * Elaborate on the types of resources.
> > * Add some descriptions for S3 and S4.
> >
> >
> > v1:
> > link,
> > https://lists.oasis-open.org/archives/virtio-comment/202306/msg00595.h
> > tml
> >
> > Hi all,
> > I am working to implement virtgpu S3 function on Xen.
> >
> > Currently on Xen, if we start a guest through Qemu with enabling
> > virtgpu, and then suspend and s3resume guest. We can find that the
> > guest kernel comes back, but the display doesn't. It just shown a black screen.
> >
> > That is because when guest was during suspending, it called into Qemu
> > and Qemu destroyed all resources and reset renderer. This made the
> > display gone after guest resumed.
> >
> > So, I add a mechanism that when guest is suspending, it will notify
> > Qemu, and then Qemu will not destroy resources. That can help guest's
> > display come back.
> >
> > As discussed and suggested by Robert Beckett and Gerd Hoffmann on v1
> > qemu's mailing list. Due to that mechanism needs cooperation between
> > guest and host. What's more, as virtio drivers by design paravirt
> > drivers, it is reasonable for guest to accept some cooperation with
> > host to manage suspend/resume. So I request to add a new feature flag,
> > so that guest and host can negotiate whenever freezing is supported or not.
> >
> > Jiqian Chen (1):
> >   virtio-gpu: Add new feature flag VIRTIO_GPU_F_FREEZE_S3
> >
> >  device-types/gpu/description.tex | 42
> > ++++++++++++++++++++++++++++++++
> >  1 file changed, 42 insertions(+)
> >
> 
> --
> Best regards,
> Jiqian Chen.