On Mon, Nov 26, 2012 at 11:03:48PM +0100, Alexander Graf wrote: > > On 26.11.2012, at 22:55, Alexander Graf wrote: > > > > > On 26.11.2012, at 22:33, Paul Mackerras wrote: > > > >> On Mon, Nov 26, 2012 at 02:15:16PM +0100, Alexander Graf wrote: > >>> > >>> On 23.11.2012, at 22:42, Paul Mackerras wrote: > >>> > >>>> On Fri, Nov 23, 2012 at 03:13:09PM +0100, Alexander Graf wrote: > >>>>> > >>>>> On 22.11.2012, at 10:25, Paul Mackerras wrote: > >>>>> > >>>>>> + /* Do they have an SLB shadow buffer registered? */ > >>>>>> + slb = vcpu->arch.slb_shadow.pinned_addr; > >>>>>> + if (!slb) > >>>>>> + return; > >>>>> > >>>>> Mind to explain this case? What happens here? Do we leave the guest > >>>>> with an empty SLB? Why would this ever happen? What happens next as > >>>>> soon as we go back into the guest? > >>>> > >>>> Yes, we leave the guest with an empty SLB, the access gets retried and > >>>> this time the guest gets an SLB miss interrupt, which it can hopefully > >>>> handle using an SLB miss handler that runs entirely in real mode. > >>>> This could happen for instance while the guest is in SLOF or yaboot or > >>>> some other code that runs basically in real mode but occasionally > >>>> turns the MMU on for some accesses, and happens to have a bug where it > >>>> creates a duplicate SLB entry. > >>> > >>> Is this what pHyp does? Also, is this what we want? Why don't we populate > >>> an #MC into the guest so it knows it did something wrong? > >> > >> Yes, yes and we do. Anytime we get a machine check while in the guest > >> we give the guest a machine check interrupt. > >> > >> Ultimately we want to implement the "FWNMI" (Firmware-assisted NMI) > >> thing defined in PAPR which makes the handling of system reset and > >> machine check slightly nicer for the guest, but that's for later. It > >> will build on top of the stuff in this patch. > > > > So why would the function return 1 then which means "MC is handled, forget > > about it" rather than 0, which means "inject MC into the guest"? > > Oh wait - 1 means "have the host handle it". Let me check up the code again.
1 means "the problem is fixed, now give the guest a machine check interrupt". 0 means "exit the guest, have the host's MC handler look at it, then give the guest a machine check". In this case the delivery of the MC to the guest happens in kvmppc_handle_exit(). Paul. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
