[lkml]   [2016]   [Jun]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH v2 3/3] KVM: VMX: enable guest access to LMCE related MSRs
On Thu, Jun 16, 2016 at 12:04:50PM +0200, Paolo Bonzini wrote:
> On 16/06/2016 08:05, Haozhong Zhang wrote:
> > From: Ashok Raj <>
> >
> > On Intel platforms, this patch adds LMCE to KVM MCE supported
> > capabilities and handles guest access to LMCE related MSRs.
> >
> > Signed-off-by: Ashok Raj <>
> > [Haozhong: macro KVM_MCE_CAP_SUPPORTED => variable kvm_mce_cap_supported
> > Only enable LMCE on Intel platform
> > Check MSR_IA32_FEATURE_CONTROL when handling guest
> > access to MSR_IA32_MCG_EXT_CTL]
> > Signed-off-by: Haozhong Zhang <>
> > @@ -6433,6 +6455,8 @@ static __init int hardware_setup(void)
> >
> > kvm_set_posted_intr_wakeup_handler(wakeup_handler);
> >
> > + kvm_mce_cap_supported |= MCG_LMCE_P;
> Ah, so virtual LMCE is available on all processors! This is
> interesting, but it also makes it more complicated to handle in QEMU; a
> new QEMU generally doesn't require a new kernel.
> Eduardo, any ideas?

(CCing libvirt list)

As we shouldn't make machine-type changes introduce new host
requirements, it looks like we need to either add a new set of
CPU models (unreasonable), or expect management software to
explicitly enable LMCE after ensuring the host supports it.

Or we could wait for a reasonable time after the feature is
available in the kernel, and declare that QEMU as a whole
requires a newer kernel. But how much time would be reasonable
for that?

Long term, I believe we should think of a better solution. I
don't think it is reasonable to require new libvirt code to be
written for every single low-level feature that requires a newer
kernel or newer host hardware. Maybe new introspection interfaces
that would allow us to drop the "no new requirements on
machine-type changes" rule?


 \ /
  Last update: 2016-06-16 17:41    [W:0.158 / U:2.032 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site