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Re: [Qemu-devel] [PATCH] kvm: fix Win2k boot without KVM
From: |
Jan Kiszka |
Subject: |
Re: [Qemu-devel] [PATCH] kvm: fix Win2k boot without KVM |
Date: |
Sat, 03 Nov 2012 21:57:13 +0100 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
On 2012-11-03 20:37, Jan Kiszka wrote:
> On 2012-11-03 20:26, Blue Swirl wrote:
>> On Sat, Nov 3, 2012 at 7:10 PM, Jan Kiszka <address@hidden> 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 <address@hidden> wrote:
>>>>>> On 2012-11-03 19:49, Blue Swirl wrote:
>>>>>>> Ignore accesses to VAPIC when kvmvapic is not enabled.
>>>>>>>
>>>>>>> Cc: Jan Kiszka <address@hidden>
>>>>>>> Signed-off-by: Blue Swirl <address@hidden>
>>>>>>> ---
>>>>>>> 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.
>
> You are on the wrong track: All is set up, the first TPR accesses are
> happening, and the kvmvapic is trying to patch them away. In TCG mode,
> this requires a flush of the current TB afterward. And this somehow
> fails, causing various issues as executing resumes at invalid addresses.
>
> Jan
>
> PS: A good hash is e.g. b34bd5e5c8f356ec206e5a306ee3a9b6f42c4315, long
> after the kvmvapic merge.
>
> PPS: Bisecting in QEMU is no fun - too many transient build breakages.
>
Bisection ended here: 0b57e287138728f72d88b06e69b970c5d745c44a
(cpu_physical_memory_write_rom() needs to do TB invalidates).
The problem is that this invalidation happens with
is_cpu_write_access=0, "consuming" the current TB for the final
invalidation in patch_instruction with is_cpu_write_access=1. So,
instead of generating a new TB and resuming execution there, the guest
jumps back to an invalidated TB.
I have a patch, but it moves half of tb_invalidate_phys_page_range to
patch_instruction. Need to check if that can be solved cleaner.
Jan
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- [Qemu-devel] [PATCH] kvm: fix Win2k boot without KVM, Blue Swirl, 2012/11/03
- Re: [Qemu-devel] [PATCH] kvm: fix Win2k boot without KVM, Jan Kiszka, 2012/11/03
- Re: [Qemu-devel] [PATCH] kvm: fix Win2k boot without KVM, Blue Swirl, 2012/11/03
- Re: [Qemu-devel] [PATCH] kvm: fix Win2k boot without KVM, Jan Kiszka, 2012/11/03
- Re: [Qemu-devel] [PATCH] kvm: fix Win2k boot without KVM, Blue Swirl, 2012/11/03
- Re: [Qemu-devel] [PATCH] kvm: fix Win2k boot without KVM, Jan Kiszka, 2012/11/03
- Re: [Qemu-devel] [PATCH] kvm: fix Win2k boot without KVM, Blue Swirl, 2012/11/03
- Re: [Qemu-devel] [PATCH] kvm: fix Win2k boot without KVM, Jan Kiszka, 2012/11/03
- Re: [Qemu-devel] [PATCH] kvm: fix Win2k boot without KVM,
Jan Kiszka <=
- Re: [Qemu-devel] [PATCH] kvm: fix Win2k boot without KVM, Jan Kiszka, 2012/11/03