On Tue, Apr 06, 2021, Michael Tokarev wrote: > Hi! > > It looks like this commit: > > commit 87fa7f3e98a1310ef1ac1900e7ee7f9610a038bc > Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Date: Wed Jul 8 21:51:54 2020 +0200 > > x86/kvm: Move context tracking where it belongs > > Context tracking for KVM happens way too early in the vcpu_run() > code. Anything after guest_enter_irqoff() and before guest_exit_irqoff() > cannot use RCU and should also be not instrumented. > > The current way of doing this covers way too much code. Move it closer to > the actual vmenter/exit code. > > broke kvm guest cpu time accounting - after this commit, when running > qemu-system-x86_64 -enable-kvm, the guest time (in /proc/stat and > elsewhere) is always 0. > > I dunno why it happened, but it happened, and all kernels after 5.9 > are affected by this. > > This commit is found in a (painful) git bisect between kernel 5.8 and 5.10. Yes :-( There's a bugzilla[1] and two proposed fixes[2][3]. I don't particularly like either of the fixes, but an elegant solution hasn't presented itself. Thomas/Paolo, can you please weigh in? [1] https://bugzilla.kernel.org/show_bug.cgi?id=209831 [2] https://lkml.kernel.org/r/1617011036-11734-1-git-send-email-wanpengli@xxxxxxxxxxx [3] https://lkml.kernel.org/r/20210206004218.312023-1-seanjc@xxxxxxxxxx
