Re: [Xen-devel] [PATCH v2 09/12] x86/vmce, tools/libxl: expose LMCE capability in guest MSR_IA32_MCG_CAP

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

On 03/20/17 18:27 +0000, Ian Jackson wrote:
> Haozhong Zhang writes ("[PATCH v2 09/12] x86/vmce, tools/libxl: expose LMCE 
> capability in guest MSR_IA32_MCG_CAP"):
> > If LMCE is supported by host and ' mca_caps = [ "lmce" ] ' is
> > present in xl config, the LMCE capability will be exposed in guest
> > MSR_IA32_MCG_CAP.  By default, LMCE is not exposed to guest so as to
> > keep the backwards migration compatibility.
> 
> Excluse my ignorance, but I'm not sure what MCE, MCA and LMCE are.
> I'm guessing MC = Machine Check ?
>

Yes.

> Is MCA "Machine Check Architecture" ?  Is that precisely the machinery
> for handling MCEs, or is it something else ?

Yes for both.

And LMCE stands for 'Local Machine Check Error', which is only sent to
the affected CPU, in contrast to the current ones on Intel CPU that
are broadcast to all CPUs.

> 
> I think we may need a bit of care in the user-facing interface to try
> to make the names and docs comprehensible.
>

'mca_caps' stands for capabilities of the machine check architecture
present to guest. I choose this name because the existing
intel_init_mca() uses "MCA capability" when it prints supported
capabilities, and ...

> > +=head3 x86
> > +
> > +=over 4
> > +
> > +=item B<mca_caps=[ "CAP", "CAP", ... ]>
> > +
> > +(HVM only) Enable MCA capabilities besides default ones enabled
> > +by Xen hypervisor for the HVM domain. "CAP" can be one in the
> > +following list:
> 
> Would it be incorrect to replace references to "MCA" with "MCE" (eg,
> changing "mca_caps" to "mce_caps" here) ?
>

... besides for consistency with intel_init_mca(), Intel SDM uses "the
information about the machine check architecture" (at the beginning of
section "IA32_MCG_CAP MSR", Vol 3). 'mca_caps' currently is for
capabilities indicated by IA32_MCG_CAP, so I think 'mca' is a better
name than 'mce'.

Thanks,
Haozhong

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel