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Re: [Qemu-devel] cpuid problem in upstream qemu with kvm
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] cpuid problem in upstream qemu with kvm |
Date: |
Mon, 14 Dec 2009 22:14:09 +0200 |
User-agent: |
Mutt/1.5.19 (2009-01-05) |
On Mon, Dec 14, 2009 at 10:08:38PM +0200, Gleb Natapov wrote:
> 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.
Yes. 64 bit kernel 32 bit userpace crashes with -cpu qemu64,-syscall.
> --
> Gleb.
- [Qemu-devel] cpuid problem in upstream qemu with kvm, Michael S. Tsirkin, 2009/12/14
- Re: [Qemu-devel] cpuid problem in upstream qemu with kvm, Anthony Liguori, 2009/12/14
- Re: [Qemu-devel] cpuid problem in upstream qemu with kvm, Michael S. Tsirkin, 2009/12/14
- Re: [Qemu-devel] cpuid problem in upstream qemu with kvm, Michael S. Tsirkin, 2009/12/14
- Re: [Qemu-devel] cpuid problem in upstream qemu with kvm, Anthony Liguori, 2009/12/14
- Re: [Qemu-devel] cpuid problem in upstream qemu with kvm, Michael S. Tsirkin, 2009/12/14
- Re: [Qemu-devel] cpuid problem in upstream qemu with kvm, Anthony Liguori, 2009/12/14
- Re: [Qemu-devel] cpuid problem in upstream qemu with kvm, Michael S. Tsirkin, 2009/12/14
- Re: [Qemu-devel] cpuid problem in upstream qemu with kvm, Anthony Liguori, 2009/12/14
- Re: [Qemu-devel] cpuid problem in upstream qemu with kvm, Michael S. Tsirkin, 2009/12/15
- Re: [Qemu-devel] cpuid problem in upstream qemu with kvm, Anthony Liguori, 2009/12/15
- Re: [Qemu-devel] cpuid problem in upstream qemu with kvm, Michael S. Tsirkin, 2009/12/15
- Re: [Qemu-devel] cpuid problem in upstream qemu with kvm, Avi Kivity, 2009/12/20