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Date: Thu, 25 Jun 2009 00:32:03 +0200
From: Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [Qemu-devel] allow sysenter on 32bit guests running on vmx host
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To: Jamie Lokier <jamie@shareable.org>
Cc: qemu-devel@nongnu.org

On Wed, Jun 24, 2009 at 10:39:44PM +0100, Jamie Lokier wrote:
> What's missing is a comment saying "KVM changes this vendor id to
> Intel when run on a VMX-capable host".

Ok.

> So what happens if you have a guest which worked fine under QEMU, then
> breaks because it sees a changed vendor id when you run it under KVM?

For windows to run sysenter, the vendor id has to be intel.

> It looks like it could be a KVM mis-feature.

If we don't turn to intel it won't ever run sysenter I think, AMD
duron/athlon has syscall, not sysenter.

> Is the changing vendor id actually useful for anything, without
> updating the family/model/stepping at the same time?  E.g. does it

Sure it is useful, without the switch not even linux can run sysenter.

> No, I'm happy with 6/3/3.  Like that part of the patch :-)

Then just update the comment to clarify that on kvm we need vendor id
intel if run on intel host ;)

> Although... there aren't any 64-bit Pentium Pros, so maybe 6/3/3 is a
> bit... small? :-)

Yes, I thought about it, but I didn't want to make more aggressive
changes other than the sysenter fix.