Messages in this thread | | | Date | Tue, 01 Nov 2011 14:28:31 -0500 | From | Anthony Liguori <> | Subject | Re: [PATCH 2/6 V2] Add functions to check if the host has stopped the vm |
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On 10/31/2011 03:07 PM, Eric B Munson wrote: > When a host stops or suspends a VM it will set a flag to show this. The > watchdog will use these functions to determine if a softlockup is real, or the > result of a suspended VM. > > Signed-off-by: Eric B Munson<emunson@mgebm.net> > --- > arch/x86/include/asm/pvclock.h | 2 ++ > arch/x86/kernel/kvmclock.c | 19 +++++++++++++++++++ > 2 files changed, 21 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h > index c59cc97..7d3ba41 100644 > --- a/arch/x86/include/asm/pvclock.h > +++ b/arch/x86/include/asm/pvclock.h > @@ -13,6 +13,8 @@ void pvclock_read_wallclock(struct pvclock_wall_clock *wall, > struct timespec *ts); > void pvclock_resume(void); > > +bool kvm_check_and_clear_host_stopped(int cpu);
A kvm-specific function shouldn't be declared in pvclock.h as this is shared code between KVM and Xen.
> + > /* > * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction, > * yielding a 64-bit result. > diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c > index c1a0188..8ddcfaf 100644 > --- a/arch/x86/kernel/kvmclock.c > +++ b/arch/x86/kernel/kvmclock.c > @@ -113,6 +113,25 @@ static void kvm_get_preset_lpj(void) > preset_lpj = lpj; > } > > +bool kvm_check_and_clear_host_stopped(int cpu) > +{ > + 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 =&per_cpu(hv_clock, cpu); > + if ((src->flags& PVCLOCK_GUEST_STOPPED) != 0) { > + src->flags = src->flags& (~PVCLOCK_GUEST_STOPPED); > + ret = true; > + }
It would be helpful to separate out the patches for guest enablement from host enablement. This is a guest function, correct?
Don't you need an atomic getandset here? Can the host clear this flag or only set it?
It's ashame we don't have a proper pvclock spec in Documentation/. I would suggest at least adding a description of how this bit works in the first patch.
Regards,
Anthony Liguori
> + > + return ret; > +} > + > static struct clocksource kvm_clock = { > .name = "kvm-clock", > .read = kvm_clock_get_cycles,
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