Re: [kvm-devel] [PATCH 2/3] Refactor hypercall infrastructure (v3)

[Avi Kivity <avi@qumranet.com>]

Avi Kivity wrote:
> Anthony Liguori wrote:
>   
> > This patch refactors the current hypercall infrastructure to better support live
> > migration and SMP.  It eliminates the hypercall page by trapping the UD
> > exception that would occur if you used the wrong hypercall instruction for the
> > underlying architecture and replacing it with the right one lazily.
> >
> > It also introduces the infrastructure to probe for hypercall available via
> > CPUID leaves 0x40000000.  CPUID leaf 0x40000001 should be filled out by
> > userspace.
> >
> > A fall-out of this patch is that the unhandled hypercalls no longer trap to
> > userspace.  There is very little reason though to use a hypercall to communicate
> > with userspace as PIO or MMIO can be used.  There is no code in tree that uses
> > userspace hypercalls.
> >
> >   
> >     
>
>
> Surprisingly, this patch kills Windows XP (ACPI HAL).  I'll try to find 
> out why.
>
>   

Not trapping #UD brings things back to normal.  So, Windows likes to 
execute undefined instructions, and we don'd handle these well.

I really should start asking for unit tests for these kinds of things 
(execute undefined instruction, see the #UD, say ok).

--
error compiling committee.c: too many arguments to function

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