Re: [Qemu-devel] cpuid problem in upstream qemu with kvm

[Gleb Natapov]

On Mon, Dec 14, 2009 at 02:02:03PM -0600, Anthony Liguori wrote:
> Gleb Natapov wrote:
> >>I thought KVM emulates the syscall instruction?  I swear I've seen
> >>patches for that.
> >>
> >It is. Starting from 2.6.32.
> 
> Okay, so this is a performance vs. migration compatibility issue then?
> 
> BTW, couldn't we just not advertise syscall in cpuid?  That should
> fix it too without sacrificing migration compatibility.  We get a
> slight slowdown on AMD hosts but that's probably minor compared to
> the cost of using emulated syscall on Intel hosts.
> 
As far as I understand not advertising syscall for 64bit CPU is not a
valid option.

--
                        Gleb.