On Wed, Jun 01, 2022 at 10:21:51AM -0600, Alex Williamson wrote: > Some ioctls clearly cannot occur while the device is in low power, such > as resets and interrupt control, but even less obvious things like > getting region info require device access. Migration also provides a > channel to device access. I wonder what power management means in a case like that. For the migration drivers they all rely on a PF driver that is not VFIO, so it should be impossible for power management to cause the PF to stop working. I would expect any sane design of power management for a VF to not cause any harm to the migration driver.. > I'm also still curious how we're going to handle devices that cannot > return to low power such as the self-refresh mode on the GPU. We can > potentially prevent any wake-ups from the vfio device interface, but > that doesn't preclude a wake-up via an external lspci. I think we need > to understand how we're going to handle such devices before we can > really complete the design. AIUI, we cannot disable the self-refresh > sleep mode without imposing unreasonable latency and memory > requirements on the guest and we cannot retrigger the self-refresh > low-power mode without non-trivial device specific code. It begs the question if power management should be something that only a device-specific drivers should allow? Jason
