Hi, > -----Original Message----- > From: Radim Krcmar [mailto:rkrc...@redhat.com] > Subject: Re: [PATCH] rtc: introduce nmi disable bit handler for cmos > > 2015-12-15 05:43-0500, Paolo Bonzini: > >> Hi Paolo, > >> > >> /* for KVM_GET/SET_VCPU_EVENTS */ > >> struct kvm_vcpu_events { > >> ... > >> struct { > >> __u8 injected; > >> __u8 pending; > >> __u8 masked; > >> __u8 pad; > >> } nmi; > >> ... > >> > >> I found that the nmi.masked property does these enable or disable NMI > jobs. > >> So, I think we don't need to add a new bit. Right? > > > > nmi.masked says whether the CPU is accepting the NMIs, and is cleared > > by the next IRET instruction. This is a different thing; it probably > > shouldn't affect NMI IPIs, and it definitely should remain set until > > cleared via the RTC. So it should be something like > > > > _u8 external_nmi_disabled; > > > > or similar. > > OK, I see, thanks.
> > *However* I found this in the ICH9 datasheet: > > > > The ICH9's I/O APIC can only send interrupts due to interrupts which > > do not include SMI, NMI or INIT. This means that in IA-32/Intel ® 64 > > based platforms, Front Side Bus interrupt message format delivery > modes > > 010 (SMI/PMI), 100 (NMI), and 101 (INIT) as indicated in this section, > > must not be used and is not supported. > > > > In theory the PIIX4 could deliver such messages, but perhaps we could > > disable them in the KVM IOAPIC. If we do this, there is no need for a > > change to struct kvm_vcpu_events, because all external NMI sources will > > be in userspace. > > > > Radim, what do you think? > > I looked at the 440fx, piix, and 82083aa(ioapic) datasheets and the > NMI_EN bit doesn't seem to be propagated into the IOAPIC. > The IOAPIC datasheet doesn't mention a thing about NMI masking and PIIX4 > generates NMI on SERR# or IOCHK# so it seems that the NMI_EN feature > only changes the behavior of those two ... > Currently, Qemu doesn't handle SERR# (bit 7) and IOCHK# (bit 6) of port 0x61. The Linux kernel gets the nmi reason when invoke default_do_nmi(), Qemu always return 0. Regards, -Gonglei > I think it's best to do nothing in KVM. > > (q35 guests shouldn't configure IOAPIC to send unsupported messages and > disabling SMI/NMI/INIT in the in-kernel IOAPIC for piix is risky.)
