On Thu, 2010-07-08 at 16:16 +0800, Avi Kivity wrote: > On 07/08/2010 11:03 AM, Huang Ying wrote: > > On Thu, 2010-07-08 at 15:43 +0800, Avi Kivity wrote: > > > >> On 07/08/2010 05:07 AM, Huang Ying wrote: > >> > >>> > >>>> static u32 emulated_msrs[] = { > >>>> MSR_IA32_MISC_ENABLE, > >>>> + MSR_IA32_MCG_STATUS, > >>>> + MSR_IA32_MCG_CTL, > >>>> > >>>> > >>> We need only clear MSR_IA32_MCG_STATUS during reset, but should not > >>> clear MSR_IA32_MCG_CTL. > >>> > >>> > >>> > >> Why not? > >> > > According to Intel 64 and IA32 Architectures Software Developer's Manual > > (SDM) Vol 3A (Table 9-1), machine check MSRs should be sticky across > > reset. > > > Well, my copy says: > > Machine-Check Architecture Pwr up or Reset: Undefined > INIT: Unchanged If my understanding is correct. Pwr up or Reset is cold reboot and INIT is warm reboot. So MCE can be logged after the warm reboot. > So it seems we're free to clear it. But probably the best thing would > be to have the bios initialize it to disabled state? > > Note, in any case we have to expose the MSRs for live migration. > > > Except we need some special processing for MSR_IA32_MCG_STATUS. > > > > What do you have in mind? MSR_IA32_MCG_STATUS need to be cleared across reboot. > > And if we clear MSR_IA32_MCG_CTL, the machine check reporting is > > disabled according to SDM Vol 3A, section 15.3.1.3 > > > > Won't the kernel reenable MCE? In my testing, the sequence > MCE-reset-MCE worked after the patch (whereas it would fail without it). Yes. Because kernel will reenable it. But if we only clear MSR_IA32_MCG_STATUS only, MCE-reset-MCE should work too. Best Regards, Huang Ying -- 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