On Wed, Mar 18, 2020 at 3:29 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > > Hi All, > > I'm not sure if $subject was a conscious design decision, or an oversight, > but that does not really matter. > > ATM the Atomic KMS API lacks the ability to set cursor hot-spot > coordinates. Mutter (and Weston) have tried to emulate this by shifting > the coordinates for where to draw the cursor by the hotspot-coordinates > and always using 0x0 for the hotspot. > > But this breaks the so called "seamless mouse mode" for virtual-machines > and there really is no way to fix this but to allow passing the proper > hotspot coordinates to the virtual gfx-card. Fully aware, we simply never had userspace for this. So - type weston patch - type kernel patch (iirc this might be some work of moving the hotspot coordinates from struct drm_plane to drm_plane_state) - wire up atomic property (it'd just do "CURSOR_HOT_X/Y" and be done with it, only attached to cursor planes that support it ofc) - I think all drivers supporting vm cursor hotspot are now atomic, so would be good to garbage-collect the old legacy infrastructure completely. legacy cursor ioctl will remap to the atomic call transparently like we do now already for everything else - type igt - get it all reviewed and merged. 0 design reasons for omitting this, simply Not Yet Done (tm). Cheers, Daniel > Seamless-mode consists of 2 parts: > > 1) Letting the VM-viewer window-system draw the cursor as it normally > would draw it. > > 2) Giving absolute coordinates of the mouse to the VM by e.g. emulating > an USB drawing tablet. These coordinates come from translating the > coordinates where the VM-viewer window-system is drawing the cursor > to an absolute position using the top left corner of the view as 0x0 > and the bottom right corner as max-abs-x,max-abs-y. > > 2) Means that any coordinates the window-system inside the VM passes to > the VM's gfx-card for where to draw the cursor are basically totally > ignored to avoid lag / flicker (and to not have to grab the cursor / > confine it to the VM-viewer window and to not have to warp the > pointer). > > This means that the offset added to the coordinates by e.g. mutter to > emulate the hotspot are ignored. For Seamless mouse mode to keep working > properly the window-system inside the VM need to pass the VM's gfx-card > the correct hotspot when setting the cursor. Which currently is not > possible when restricting oneself to the atomic APIs. > > Also see: https://gitlab.gnome.org/GNOME/mutter/issues/1094 > Where this is currently being tracked from the mutter side. Mutter > internally has both atomic and legacy paths. The plan for now is to > push the hotspot-emulation by shifting coordinates thing into the > atomic path, fixing seamless mouse mode when running in legacy mode, > combined with blacklisting vboxvideo, vmwgfx, qxl and cirrus from > using atomic mode. > > This is of course a workaround, eventually we would like to see > the atomic API extended to allow passing the cursor hot spot. > > I'm not really familiar enough with the atomic API to come up with > an API design for this, but if there are suggestions on how this > should look like from the uAPI side then I can take a shot at > implementing this (and hooking it up in mutter's atomic code > paths to test it). > > Regards, > > Hans > > > > p.s. > > Before people start discussing how the VM / VM-viewer is broken here and > the VM needs to be fixed. Seamless mouse mode exists for at least a > decade and has worked fine during this entire decade. It also works > fine when using the legacy (non atomic) DRM_IOCTL_MODE_CURSOR2 ioctl; > > Also this problem reproduces with 2 completely independent VM code-bases, > it has been seen on both qemu-kvm VMs and on VirtualBox VMs and I would > not be surprised if other hypervisors are also affected. > > And on the API consumer side this problem has been triggered by both > mutter and Weston. > > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
