On Mon, Jun 11, 2012 at 06:10:34PM -0400, Eric B Munson wrote:
> On Mon, 11 Jun 2012 19:07:19 -0300, Marcelo Tosatti wrote:
> >On Mon, Jun 11, 2012 at 05:47:00PM -0400, Eric B Munson wrote:
> >>On Sun, 10 Jun 2012 17:47:24 +0200, Sedat Dilek wrote:
> >>>Hi,
> >>>
> >>>I see the same warning especially when resuming from a suspend (see
> >>>timestamps >=30-35sec) between Linux v3.5-rc1..v3.5-rc2.
> >>>
> >>>$ sudo grep kvmclock.c /var/log/kern.log
> >>>Jun 4 21:11:32 fambox kernel: [ 784.037237] WARNING: at
> >>>arch/x86/kernel/kvmclock.c:127
> >>>kvm_check_and_clear_guest_paused+0x52/0x60()
> >>>Jun 5 20:35:57 fambox kernel: [ 1928.458060] WARNING: at
> >>>arch/x86/kernel/kvmclock.c:127
> >>>kvm_check_and_clear_guest_paused+0x52/0x60()
> >>>Jun 8 09:35:52 fambox kernel: [ 3290.134637] WARNING: at
> >>>arch/x86/kernel/kvmclock.c:127
> >>>kvm_check_and_clear_guest_paused+0x52/0x60()
> >>>Jun 8 09:35:52 fambox kernel: [ 3290.238592] WARNING: at
> >>>arch/x86/kernel/kvmclock.c:127
> >>>kvm_check_and_clear_guest_paused+0x52/0x60()
> >>>Jun 8 12:11:20 fambox kernel: [ 5777.023571] WARNING: at
> >>>arch/x86/kernel/kvmclock.c:127
> >>>kvm_check_and_clear_guest_paused+0x52/0x60()
> >>>Jun 9 13:32:50 fambox kernel: [ 2778.842695] WARNING: at
> >>>arch/x86/kernel/kvmclock.c:127
> >>>kvm_check_and_clear_guest_paused+0x52/0x60()
> >>>
> >>>From [1]:
> >>>
> >>>"...The warning itself is not required for the check_and_clear
> >>>function and can be removed as far as I am concerned."
> >>>
> >>>From [2] commit 3b5d56b9317fa7b5407dff1aa7b115bf6cdbd494
> >>("kvmclock:
> >>>Add functions to check if the host has stopped the vm")
> >>>...
> >>>+bool kvm_check_and_clear_guest_paused(void)
> >>>+{
> >>>+ bool ret = false;
> >>>+ struct pvclock_vcpu_time_info *src;
> >>>+
> >>>+ /*
> >>>+ * per_cpu() is safe here because this function is only
> >>>called from
> >>>+ * timer functions where preemption is already disabled.
> >>>+ */
> >>>+ WARN_ON(!in_atomic());
> >>>+ src = &__get_cpu_var(hv_clock);
> >>>+ if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) {
> >>>+ __this_cpu_and(hv_clock.flags,
> >>>~PVCLOCK_GUEST_STOPPED);
> >>>+ ret = true;
> >>>+ }
> >>>+
> >>>+ return ret;
> >>>+}
> >>>+EXPORT_SYMBOL_GPL(kvm_check_and_clear_guest_paused);
> >>>+
> >>>...
> >>>( The export macro was dropped in a followup commit. )
> >>>
> >>>So you mean "WARN_ON(!in_atomic());" can be deleted?
> >
> >Yes.
> >
> >>When I wrote the patch originally, I was under the (incorrect)
> >>assumption that the watch dog was only ever reset in an atomic
> >>context. Given that this is not the case, the warning can be
> >>removed. Though before that happens, I have a question: if this is
> >>called outside of an atomic context, is the use of __get_cpu_Var()
> >>and __this_cpu_and() invalid?
> >
> >It remains valid because its called with interrupts
> >disabled (see migrate_hrtimers).
>
> Thank you, that was my assumption but I wanted to confirm. I do not
> have access to my working kernel tree and won't for 2 days. I can't
> get to the patch until late Wednesday so if someone else wants to
> work that up I'd appreciate it.
>
> Thanks,
> Eric
Removed the warning in kvm.git master.
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