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

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

On 2011-02-02 15:43, Jan Kiszka wrote:
> 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  Userspace APIC is broken since it may run with an outdated cr8, does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?

Hmm, probably rather that there is a discrepancy between tpr and irr.
The latter is changed asynchronously /wrt to the vcpu, the former /wrt
the user space device model.

Run apic_set_irq on the vcpu?

Jan

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