From mboxrd@z Thu Jan 1 00:00:00 1970 From: Scott Wood Subject: Re: [PATCH 2/2 v2] KVM: PPC: booke: Add watchdog emulation Date: Tue, 17 Jul 2012 12:00:39 -0500 Message-ID: <50059A37.10004@freescale.com> References: <1341830087-12728-1-git-send-email-Bharat.Bhushan@freescale.com> <50044CF1.8070806@suse.de> <5004B995.8060303@freescale.com> <6A3DF150A5B70D4F9B66A25E3F7C888D03DCB1A9@039-SN2MPN1-023.039d.mgd.msft.net> <500594CF.9070601@freescale.com> <6A3DF150A5B70D4F9B66A25E3F7C888D03DCBABD@039-SN2MPN1-023.039d.mgd.msft.net> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Wood Scott-B07421 , Alexander Graf , "kvm-ppc@vger.kernel.org" , "kvm@vger.kernel.org" , "bharatb.yadav@gmail.com" , Benjamin Herrenschmidt , Kumar Gala To: Bhushan Bharat-R65777 Return-path: In-Reply-To: <6A3DF150A5B70D4F9B66A25E3F7C888D03DCBABD@039-SN2MPN1-023.039d.mgd.msft.net> Sender: kvm-ppc-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 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@vger.kernel.org; >> kvm@vger.kernel.org; bharatb.yadav@gmail.com; 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. > But interrupt will not be delivered to guest and Final expiry can still cause reset etc !! Right? Not sure what your point is -- yes, if the interrupt is masked it will not be delivered to the guest, and the enforcement mechanism of the watchdog is still active. >>> And we want that if TSR.WRS update >>> wins the race with clearing of watchdog interrupt condition from guest >>> then anyways let QEMU exit with reason KVM_EXIT_WDT? >> >> What race? If ENW and WIS are both set when the watchdog timer fires, it's a >> final expiration. It's irrelevant what happens to WIS after that point, before >> enforcement kicks in. > > What I was thinking of was if we can remove this check in vcpu_runnable() and use watchdog bit in pending_exception to qualify vcpu_runnable() No, we want a new bit. -Scott