> -----Original Message----- > From: kvm-ppc-owner@xxxxxxxxxxxxxxx [mailto:kvm-ppc- > owner@xxxxxxxxxxxxxxx] On Behalf Of Alexander Graf > Sent: Wednesday, May 16, 2012 6:18 PM > To: Sethi Varun-B16395 > Cc: Bhushan Bharat-R65777; kvm-ppc@xxxxxxxxxxxxxxx > Subject: Re: [PATCH] KVM: PPC: Not optimizing MSR_CE and MSR_DE with > paravirt. > > On 05/16/2012 02:27 PM, Sethi Varun-B16395 wrote: > > > >> -----Original Message----- > >> From: kvm-ppc-owner@xxxxxxxxxxxxxxx [mailto:kvm-ppc- > >> owner@xxxxxxxxxxxxxxx] On Behalf Of Alexander Graf > >> Sent: Wednesday, May 16, 2012 2:42 PM > >> To: Bhushan Bharat-R65777 > >> Cc: kvm-ppc@xxxxxxxxxxxxxxx > >> Subject: Re: [PATCH] KVM: PPC: Not optimizing MSR_CE and MSR_DE with > >> paravirt. > >> > >> On 05/16/2012 10:42 AM, Bhushan Bharat-R65777 wrote: > >>>> -----Original Message----- > >>>> From: kvm-ppc-owner@xxxxxxxxxxxxxxx > >>>> [mailto:kvm-ppc-owner@xxxxxxxxxxxxxxx] On Behalf Of Alexander Graf > >>>> Sent: Tuesday, May 15, 2012 8:01 PM > >>>> To: Bhushan Bharat-R65777 > >>>> Cc: kvm-ppc@xxxxxxxxxxxxxxx; Bhushan Bharat-R65777 > >>>> Subject: Re: [PATCH] KVM: PPC: Not optimizing MSR_CE and MSR_DE > >>>> with > >> paravirt. > >>>> On 05/15/2012 09:37 AM, Bharat Bhushan wrote: > >>>>> From: Bhushan Bharat-R65777<R65777@xxxxxxxxxxxxx> > >>>>> > >>>>> If there is pending critical or machine check interrupt then guest > >>>>> would like to capture it when guest enable MSR.CE and MSR_ME > >> respectively. > >>>>> Also as mostly MSR_CE and MSR_ME are updated with rfi/rfci/rfmii > >>>>> which anyway traps so removing the the paravirt optimization for > >>>>> MSR.CE and MSR.ME. > >>>> It's only not safe for e500mc and above, right? > >>> For e500mc and above the paravirt emulation code will not come into > >> picture, And critical and machine check interrupt will happen only if > >> MSR have corresponding bits set. So they are already safe. Is not it? > >> > >> Yup, though it might be worth documenting the fact with a few > >> #ifdef's, in case anyone wants to run PR KVM on e500mc ever. > >> > > Synchronous error report machine checks don't depend on MSR[ME] in case > of e500mc. > > > >>>> E500v2 and book3s should be > >>>> fine. > >>> And with this patch e500v2 will be fine? Not sure of book3s :). > >> Well, e500v2 has edge triggered MCs, no? MSR.CE is unsafe however, as > >> criticals are basically the same as externals. > >> > > In case of e500v2 machine check would be reported if MSR[ME], but if > > MSR[ME] is not set the core would enter a check stop state. Yes, > machine checks on e500v2 are edge triggered. > > Why is MSR[CE] unsafe? > > MSR=0 > * critical interrupt comes in * > mtmsr(MSR_CE) > --> MSR == MSR_CE > * interrupt should be delivered, but host doesn't get notified that > MSR_CE is changing * > > However, we completely ignore critical interrupts in KVM these days, no? > Well, it's least likely that MSR_CE/MSR_ME would get changed directly. They would mostly get changed via rfci/rfmci, which would trap. -Varun -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
