Messages in this thread | | | From | Arnd Bergmann <> | Date | Wed, 10 Feb 2021 14:32:19 +0100 | Subject | Re: [RFC PATCH 0/2] Introduce a way to adjust CLOCK_BOOTTIME from userspace for VM guests |
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On Wed, Feb 10, 2021 at 11:39 AM Hikaru Nishida <hikalium@chromium.org> wrote: > From: Hikaru Nishida <hikalium@chromium.org> > > We'd like to add a sysfs interface that enable us to advance > CLOCK_BOOTTIME from userspace. The use case of this change is that > adjusting guest's CLOCK_BOOTTIME as host suspends to ensure that the > guest can notice the device has been suspended. > We have an application that rely on the difference between > CLOCK_BOOTTIME and CLOCK_MONOTONIC to detect whether the device went > suspend or not. However, the logic did not work well on VM environment > since most VMs are pausing the VM guests instead of actually suspending > them on the host's suspension. > With following patches, we can adjust CLOCK_BOOTTIME without actually > suspending guest and make the app working as intended. > I think this feature is also useful for other VM solutions since there > was no way to do this from userspace. > > As far as I checked, it is working as expected but is there any concern > about this change? If so, please let me know.
I think the correct internal interface to call would be timekeeping_inject_sleeptime64(), which changes boottime in a safe way.
Not sure what should call it, but kvmclock as Alex suggested might be the right place.
Arnd
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