Re: [Qemu-devel] [PATCH] kvm: fix Win2k boot without KVM

[Blue Swirl <blauwirbel@gmail.com>]

On Sat, Nov 3, 2012 at 7:10 PM, Jan Kiszka <jan.kiszka@web.de> wrote:
> On 2012-11-03 20:03, Jan Kiszka wrote:
>> On 2012-11-03 19:56, Blue Swirl wrote:
>>> On Sat, Nov 3, 2012 at 6:51 PM, Jan Kiszka <jan.kiszka@web.de> wrote:
>>>> On 2012-11-03 19:49, Blue Swirl wrote:
>>>>> Ignore accesses to VAPIC when kvmvapic is not enabled.
>>>>>
>>>>> Cc: Jan Kiszka <jan.kiszka@web.de>
>>>>> Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
>>>>> ---
>>>>>  hw/kvmvapic.c |    7 ++++---
>>>>>  1 files changed, 4 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/hw/kvmvapic.c b/hw/kvmvapic.c
>>>>> index dc111ee..a97d532 100644
>>>>> --- a/hw/kvmvapic.c
>>>>> +++ b/hw/kvmvapic.c
>>>>> @@ -612,6 +612,9 @@ static void vapic_write(void *opaque, hwaddr addr, uint64_t data,
>>>>>      hwaddr rom_paddr;
>>>>>      VAPICROMState *s = opaque;
>>>>>
>>>>> +    if (!kvm_irqchip_in_kernel()) {
>>>>> +        return;
>>>>> +    }
>>>>>      cpu_synchronize_state(env);
>>>>>
>>>>>      /*
>>>>> @@ -665,9 +668,7 @@ static void vapic_write(void *opaque, hwaddr addr, uint64_t data,
>>>>>          break;
>>>>>      default:
>>>>>      case 4:
>>>>> -        if (!kvm_irqchip_in_kernel()) {
>>>>> -            apic_poll_irq(env->apic_state);
>>>>> -        }
>>>>> +        apic_poll_irq(env->apic_state);
>>>>>          break;
>>>>>      }
>>>>>  }
>>>>>
>>>>
>>>> NACK, I'm already debugging the true reason (related to code patching).
>>>
>>> This is a minimal fix that lets Win2k boot, now it does not work at
>>> all. I think it should be applied for 1.3, it can be reverted when
>>> (if) you find a better fix. There's no hurry though.
>>
>> If you want to disable it, flip apic.vapic for !kvm_enabled. Your patch
>> affects user space APIC with KVM as well, though that is perfectly fine.
>>
>> But first of all give this some days as I just started.
>
> ...even more as this regression may not be related to the introduction
> of the kvmvapic: My original test case for the kvmvapic under TCG,
> WinXP, is now also broken, causing a segfault too.
>
> What I'm seeing is that tb_invalidate_phys_page_range in
> patch_instruction no longer seems to detect that the currently executed
> tb was just changed. Any ideas what may cause this are welcome.

My theory is that the kvmvapic ROM tries to make the PIO hypercalls,
but the PIO devices in QEMU are not ready, maybe not initialized at
all.

>
> Jan
>