On 07/17/2012 12:10 PM, Bhushan Bharat-R65777 wrote: > > >> -----Original Message----- >> From: Wood Scott-B07421 >> Sent: Tuesday, July 17, 2012 10:31 PM >> To: Bhushan Bharat-R65777 >> Cc: Wood Scott-B07421; Alexander Graf; kvm-ppc@xxxxxxxxxxxxxxx; >> kvm@xxxxxxxxxxxxxxx; bharatb.yadav@xxxxxxxxx; Benjamin Herrenschmidt; Kumar Gala >> Subject: Re: [PATCH 2/2 v2] KVM: PPC: booke: Add watchdog emulation >> >> On 07/17/2012 11:56 AM, Bhushan Bharat-R65777 wrote: >>> >>> >>>> -----Original Message----- >>>> From: Wood Scott-B07421 >>>> Sent: Tuesday, July 17, 2012 10:08 PM >>>> To: Bhushan Bharat-R65777 >>>> Cc: Wood Scott-B07421; Alexander Graf; kvm-ppc@xxxxxxxxxxxxxxx; >>>> kvm@xxxxxxxxxxxxxxx; bharatb.yadav@xxxxxxxxx; Benjamin Herrenschmidt; >>>> Kumar Gala >>>> Subject: Re: [PATCH 2/2 v2] KVM: PPC: booke: Add watchdog emulation >>>> >>>> On 07/17/2012 06:31 AM, Bhushan Bharat-R65777 wrote: >>>>>>>> int kvm_arch_vcpu_runnable(struct kvm_vcpu *v) { >>>>>>>> - return !(v->arch.shared->msr & MSR_WE) || >>>>>>>> - !!(v->arch.pending_exceptions) || >>>>>>>> - v->requests; >>>>>>>> + bool ret = !(v->arch.shared->msr & MSR_WE) || >>>>>>>> + !!(v->arch.pending_exceptions) || >>>>>>>> + v->requests; >>>>>>>> + >>>>>>>> + ret = ret || kvmppc_get_tsr_wrc(v); >>>>>>> >>>>>>> Why do you need to declare the cpu as non-runnable when a watchdog >>>>>>> event occured? >>>>>> >>>>>> It's the other way around -- it's always runnable when a watchdog >>>>>> exit is pending. It's like a pending exception. >>>>> >>>>> With the above check, Are we trying to handle the case where >>>>> watchdog interrupt bit in pending_exception is cleared by guest >>>>> after final expiry but before the qemu exit? >>>> >>>> No, we're just trying to test the actual condition we want to exit on. >>>> The watchdog interrupt might be masked (either with WIE or CE). >>> >>> If the interrupt is masked then still the pending_exception will be set. >> >> Not if it's masked by WIE -- and even when masked by CE, it's a bug that we >> currently consider the vcpu runnable. We shouldn't depend on that bug. > > Scott can you please describe what is bug? If an interrupt is masked by EE, CE, ME, etc. it is still in pending_exceptions, so runnable still returns true, and we can't go idle. > What I remember is that if > vcpu is not run-able then we halt vcpu and cannot cause qemu exit > also. I agree that we want to be considered runnable if we have a final expiration with an action. What I disagree with is using the same pending_exceptions bit as is used for the ordinary watchdog interrupt. They're not the same thing. -Scott -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html