Re: [PATCH 1/2] KVM: x86 emulator: don't update vcpu state if instruction is restarted.

Avi Kivity
2010-08-01T12:35:43Z

On 08/01/2010 03:23 PM, Gleb Natapov wrote:
> On Sun, Aug 01, 2010 at 03:17:10PM +0300, Avi Kivity wrote:
>> On 08/01/2010 01:53 PM, Gleb Natapov wrote:
>>>> That requires everyone to update, or suffer major breakage.
>>>>
>>> They will suffer major breakage when they update to a kvm that calls to
>>> kvm-tpr-opt.c from emulator anyway.
>> Why?
>>
> Because tpr code will be called with wrong rip. Emulator always updated rip at the end
> of an instruction emulation in writeback stage.
>

We can change it before switching enabling e_i_g_s by default.

>>> So what can we do about it?
>>>
>> Keep the existing behaviour.
>>
> Existing behaviour will cause breakage.
>

The existing user-visible behaviour. The user doesn't know whether the
emulator is involved or not.

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