On Tue, Mar 25, 2025 at 4:07 AM David Woodhouse <dwmw2@xxxxxxxxxxxxx> wrote: > > On Mon, 2025-03-24 at 15:54 -0700, Sean Christopherson wrote: > > > > David can confirm, but I'm pretty sure the drift you are observing is addressed > > by David's series to fix a plethora of kvmclock warts. > > > > https://lore.kernel.org/all/20240522001817.619072-1-dwmw2@xxxxxxxxxxxxx > > Yes, that looks like exactly the problem my series is addressing. We > shouldn't update the pvclock so often. And if/when we do, we shouldn't > clamp it to some *other* clock which progresses at a different rate to > the pvclock, because that causes steps in the pvclock. I applied the patch series on top of 6.9 cleanly and tested it with my debug tool patch. But it seems the time drift still increased monotonically. Would you help take a look if the tool patch makes sense? https://github.com/minggr/linux/commit/5284a211b6bdc9f9041b669539558a6a858e88d0 The tool patch adds a KVM debugfs entry to trigger time calculations and print the results. See my first email for more detail. Test Script: #!/bin/bash qemu_pid=$(pidof qemu-system-x86_64) while [ 1 ] ; do echo "=====================================" echo "Guest OS running time: $(ps -p $qemu_pid -o etime= | awk '{print $1}')" cat /sys/kernel/debug/kvm/*/pvclock echo sleep 10 done Thanks, Ming
