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Date: Fri, 07 Nov 2008 18:01:38 +0100
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] kvm: sync registers?
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	<200811071631.54494.paul@codesourcery.com>
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To: qemu-devel@nongnu.org

Paul Brook wrote:
> On Friday 07 November 2008, Anthony Liguori wrote:
>> Gerd Hoffmann wrote:
>>>   Hi,
>>>
>>> How does kvm sync registers between kernel and qemu env?
>>> I see there are kvm_arch_{get,put}_registers() functions in
>>> target-i386/kvm.c, but grep doesn't find a single call of them?
>> Right now, it doesn't.  We should probably sync registers in the same
>> places that kvm-userspace does (gdbstubs, vmport, etc.).
>>
>> I tried to always sync registers on every exit but this causes boot to
>> fail. The same is true of kvm-userspace though and I've been meaning to
>> dig into why this is.
> 
> Maybe due to do with inconsistencies between the segment register contents and 
> the descriptor tables? I know I've written code that relies on this feature.

Unlikely.  xenner depends on that too, and also on kvm supporting it.
start-of-day actually sets up the segment registers only, not any
descriptor tables, then starts the guest in protected mode.