Hi Thomas,
> Subject: Re: [RFC][PATCH] drm/virtgpu: Make vblank event dependent on
> the host resource
>
> >>
> >> On 10/17/25 10:38, Thomas Zimmermann wrote:
> >> ...
> >>> There's little difference between the current event handling and the
> one
> >>> where no vblanks have been set up. I suspect that the vblank timer
> >>> callback interferes with the locking in atomic_flush. That would also
> >>> explain why the fps drop at no clear pattern.
> >>>
> >>> Could you please test the attached patch? It enables/disables the
> vblank
> >>> timer depending on the buffer resources; as you suggested
> before. Does
> >>> this make a difference?
> >> The attached patch doesn't work, please see the trace below.
> >>
> >> @Vivek Please clarify whether you only see frames drop with your
> >> multi-gpu guest-blob setup or with a usual virgl too. I haven't noticed
> >> problem with frames pacing for virgl and nctx modes yesterday, will
> >> check again.
> > On a second look, I now see that this RFC (not the attached) patch
> > doesn't work properly with host blobs.
> >
> > I'm getting 100-150fps with this patch applied instead of expected
> > 60fps. Without this RFC patch I'm getting constant 60fps with native
> > context displaying host blobs.
> >
> > Not sure why guest blob would behave differently from the host blob.
> > Suspect something if off with the prime sharing that Vivek uses in the
> > vfio testing setup. I'd suggest to disable vblank timer only for guest
> > blobs if no quick solution will be found.
>
> After reading your reply and Vivek's new results, I'm confused now. Does
> it work or is there another patch needed?
Considering my use-case and Dmitry's virgl/venus/native context use-cases
and the benefits offered by vblank timer in these different scenarios, I think
the following patch should be sufficient for now:
diff --git a/drivers/gpu/drm/virtio/virtgpu_display.c
b/drivers/gpu/drm/virtio/virtgpu_display.c
index e972d9b015a9..c1a8f88f0a20 100644
--- a/drivers/gpu/drm/virtio/virtgpu_display.c
+++ b/drivers/gpu/drm/virtio/virtgpu_display.c
@@ -102,7 +102,11 @@ static void virtio_gpu_crtc_mode_set_nofb(struct drm_crtc
*crtc)
static void virtio_gpu_crtc_atomic_enable(struct drm_crtc *crtc,
struct drm_atomic_state *state)
{
- drm_crtc_vblank_on(crtc);
+ struct drm_device *dev = crtc->dev;
+ struct virtio_gpu_device *vgdev = dev->dev_private;
+
+ if (!vgdev->has_resource_blob || vgdev->has_virgl_3d)
+ drm_crtc_vblank_on(crtc);
}
static void virtio_gpu_crtc_atomic_disable(struct drm_crtc *crtc,
@@ -112,7 +116,8 @@ static void virtio_gpu_crtc_atomic_disable(struct drm_crtc
*crtc,
struct virtio_gpu_device *vgdev = dev->dev_private;
struct virtio_gpu_output *output = drm_crtc_to_virtio_gpu_output(crtc);
- drm_crtc_vblank_off(crtc);
+ if (!vgdev->has_resource_blob || vgdev->has_virgl_3d)
+ drm_crtc_vblank_off(crtc);
Thanks,
Vivek
>
> Best regards
> Thomas
>
> >
>
> --
> --
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Frankenstrasse 146, 90461 Nuernberg, Germany
> GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
> HRB 36809 (AG Nuernberg)
>
