From: Thomas Zimmermann <tzimmerm...@suse.de> Sent: Thursday, September 4, 2025 7:56 AM > > Compositors often depend on vblanks to limit their display-update > rate. Without, they see vblank events ASAP, which breaks the rate- > limit feature. This creates high CPU overhead. It is especially a > problem with virtual devices with fast framebuffer access. > > The series moves vkms' vblank timer to DRM and converts the hyperv > DRM driver. An earlier version of this series contains examples of > other updated drivers. In principle, any DRM driver without vblank > hardware can use the timer.
I've tested this patch set in a Hyper-V guest against the linux-next20250829 kernel. All looks good. Results and perf are the same as reported here [4]. So far I haven't seen the "vblank timer overrun" error, which is consistent with the changes you made since my earlier testing. I'll keep running this test kernel for a while to see if anything anomalous occurs. For Patches 1, 2, and 4 of the series on a Hyper-V guest, Tested-by: Michael Kelley <mhkli...@outlook.com> [4] https://lore.kernel.org/dri-devel/20250523161522.409504-1-mhkli...@outlook.com/T/#m2e288dddaf7b3c025bbbf88da4b4c39e7aa950a7 > > The series has been motivated by a recent discussion about hypervdrm [1] > and other long-standing bug reports. [2][3] > > v3: > - fix deadlock (Ville, Lyude) > v2: > - rework interfaces > > [1] > https://lore.kernel.org/dri-devel/20250523161522.409504-1-mhkli...@outlook.com/T/#ma2ebb52b60bfb0325879349377738fadcd7cb7ef > [2] https://bugzilla.suse.com/show_bug.cgi?id=1189174 > [3] https://invent.kde.org/plasma/kwin/-/merge_requests/1229#note_284606 > > Thomas Zimmermann (4): > drm/vblank: Add vblank timer > drm/vblank: Add CRTC helpers for simple use cases > drm/vkms: Convert to DRM's vblank timer > drm/hypervdrm: Use vblank timer > > Documentation/gpu/drm-kms-helpers.rst | 12 ++ > drivers/gpu/drm/Makefile | 3 +- > drivers/gpu/drm/drm_vblank.c | 161 +++++++++++++++++- > drivers/gpu/drm/drm_vblank_helper.c | 176 ++++++++++++++++++++ > drivers/gpu/drm/hyperv/hyperv_drm_modeset.c | 11 ++ > drivers/gpu/drm/vkms/vkms_crtc.c | 83 +-------- > drivers/gpu/drm/vkms/vkms_drv.h | 2 - > include/drm/drm_modeset_helper_vtables.h | 12 ++ > include/drm/drm_vblank.h | 32 ++++ > include/drm/drm_vblank_helper.h | 56 +++++++ > 10 files changed, 467 insertions(+), 81 deletions(-) > create mode 100644 drivers/gpu/drm/drm_vblank_helper.c > create mode 100644 include/drm/drm_vblank_helper.h > > -- > 2.50.1
