On 10.02.21 11:39, Hikaru Nishida wrote:
From: Hikaru Nishida <hikalium@xxxxxxxxxxxx> Hi folks, 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 don't fully grasp why you want the guest to manually adjust its CLOCK_BOOTTIME. Wouldn't it make more sense to extend kvmclock's notion of wall clock time to tell you about suspended vs executed wall clock?
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