Re: [PATCH] KVM: x86: Add instruction length to VCPU event state

[Jan Kiszka <jan.kiszka@web.de>]

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Avi Kivity wrote:
> On 02/13/2010 11:51 AM, Jan Kiszka wrote:
>> From: Jan Kiszka<jan.kiszka@siemens.com>
>>
>> VMX requires a properly set instruction length VM entry field when
>> trying to inject soft exception and interrupts. We have to preserve this
>> state across VM save/restore to avoid breaking the re-injection of such
>> events on Intel. So add it to the new VCPU event state.
>>
>>    
> 
> Can't we fake it?  set instruction length to 1 and rewind rip by 1.
> 
> The only case where I think this can fail is if we have a fault during
> the soft exception injection.

I don't think so. If e.g. privileged soft exception delivery failed, we
happen to return to user space at this point and we then start a
migration, we have to deal with arbitrary lengths on re-injection on the
migration target.

Jan


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