On Tue, Sep 16, 2025 at 10:36:22AM +0200, Thomas Zimmermann wrote:
> HyperV's virtual hardware does not provide vblank interrupts. Use a
> vblank timer to simulate the interrupt. Rate-limits the display's
> update frequency to the display-mode settings. Avoids excessive CPU
> overhead with compositors that do not rate-limit their output.
>
> Signed-off-by: Thomas Zimmermann <tzimmerm...@suse.de>
> Reviewed-by: Javier Martinez Canillas <javi...@redhat.com>
> Tested-by: Michael Kelley <mhkli...@outlook.com>
> ---
> drivers/gpu/drm/hyperv/hyperv_drm_modeset.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c
> b/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c
> index 945b9482bcb3..6e6eb1c12a68 100644
> --- a/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c
> +++ b/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c
> @@ -19,6 +19,8 @@
> #include <drm/drm_probe_helper.h>
> #include <drm/drm_panic.h>
> #include <drm/drm_plane.h>
> +#include <drm/drm_vblank.h>
> +#include <drm/drm_vblank_helper.h>
>
> #include "hyperv_drm.h"
>
> @@ -111,11 +113,15 @@ static void hyperv_crtc_helper_atomic_enable(struct
> drm_crtc *crtc,
> crtc_state->mode.hdisplay,
> crtc_state->mode.vdisplay,
> plane_state->fb->pitches[0]);
> +
> + drm_crtc_vblank_on(crtc);
> }
>
> static const struct drm_crtc_helper_funcs hyperv_crtc_helper_funcs = {
> .atomic_check = drm_crtc_helper_atomic_check,
> + .atomic_flush = drm_crtc_vblank_atomic_flush,
> .atomic_enable = hyperv_crtc_helper_atomic_enable,
> + .atomic_disable = drm_crtc_vblank_atomic_disable,
> };
>
> static const struct drm_crtc_funcs hyperv_crtc_funcs = {
> @@ -125,6 +131,7 @@ static const struct drm_crtc_funcs hyperv_crtc_funcs = {
> .page_flip = drm_atomic_helper_page_flip,
> .atomic_duplicate_state = drm_atomic_helper_crtc_duplicate_state,
> .atomic_destroy_state = drm_atomic_helper_crtc_destroy_state,
> + DRM_CRTC_VBLANK_TIMER_FUNCS,
> };
>
> static int hyperv_plane_atomic_check(struct drm_plane *plane,
> @@ -321,6 +328,10 @@ int hyperv_mode_config_init(struct hyperv_drm_device *hv)
> return ret;
> }
>
> + ret = drm_vblank_init(dev, 1);
> + if (ret)
> + return ret;
> +
> drm_mode_config_reset(dev);
>
> return 0;
>
> --
> 2.51.0
>
Tested this series.
On a Hyper-V VM running Ubuntu,
with this patch
$ time find /
real 0m13.911s
user 0m0.965s
sys 0m3.815s
without this patch
$ time find /
real 0m14.254s
user 0m0.954s
sys 0m3.863s
Tested-by: Prasanna Kumar T S M <p...@linux.microsoft.com>
