Re: [Qemu-devel] KVM: Windows 64-bit troubles with user space irqchip

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2011-02-02 15:35, Avi Kivity wrote:
> On 02/02/2011 04:30 PM, Jan Kiszka wrote:
>> On 2011-02-02 14:05, Avi Kivity wrote:
>>>  On 02/02/2011 02:50 PM, Jan Kiszka wrote:
>>>>>>
>>>>>   Opps, -smp 1. With -smp 2 it boot almost completely and then hangs.
>>>>
>>>>  Ah, good (or not good). With Windows 2003 Server, I actually get a Blue
>>>>  Screen (Stop 0x000000b8).
>>>
>>>  Userspace APIC is broken since it may run with an outdated cr8, does
>>>  reverting 27a4f7976d5 help?
>>
>> Can you elaborate on what is broken? The way hw/apic.c maintains the
>> tpr? Would it make sense to compare this against the in-kernel model? Or
>> do you mean something else?
> 
> The problem, IIRC, was that we look up the TPR but it may already have 
> been changed by the running vcpu.  Not 100% sure.
> 
> If that is indeed the problem then the fix would be to process the APIC 
> in vcpu context (which is what the kernel does - we set a bit in the IRR 
> and all further processing is synchronous).

You mean: user space changes the tpr value while the vcpu is in KVM_RUN,
then we return from the kernel and overwrite the tpr in the apic with
the vcpu's view, right?

Jan

-- 
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux