Re: [Qemu-devel] Win2k broken by kvmvapic

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

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On 2012-10-07 20:40, Blue Swirl wrote:
> On Sun, Oct 7, 2012 at 5:24 PM, Jan Kiszka <jan.kiszka@web.de> wrote:
>> On 2012-10-07 17:23, Blue Swirl wrote:
>>> Hi,
>>>
>>> Win2k does not work in HEAD, it resets the machine. I bisected this to
>>> 0b57e287138728f72d88b06e69b970c5d745c44a, but that does not look so
>>> buggy.
>>>
>>> Digging deeper, the problem is introduced by kvmvapic:
>>> Breakpoint 1, cpu_physical_memory_write_rom (addr=0xca300,
>>>     buf=0x7fffec66b500 "", len=0x5) at /src/qemu/exec.c:3536
>>> 3536                invalidate_and_set_dirty(addr1, l);
>>> (gdb) bt
>>> #0  cpu_physical_memory_write_rom (addr=0xca300, buf=0x7fffec66b500 "",
>>>     len=0x5) at /src/qemu/exec.c:3536
>>> #1  0x0000000000644089 in apic_sync_vapic (s=0x1a6ba60, sync_type=0x2)
>>>     at /src/qemu/hw/i386/../apic.c:132
>>>
>>> It looks like vapic is enabled even with KVM disabled
>>
>> Which is intentional. The VAPIC is provided in a KVM-independent way to
>> the guest. Used to work fine with XP, but I never had my finger on a 2k
>> version.
>>
>>> and this causes
>>> chaos. With -global apic.vapic=false Win2k works.
>>
>> And that means we have a bug somewhere. Can you specify the chaos you
>> see in more details? Does your Win2k boot with KVM (and kvmvapic)?
> 
> It works with KVM both with and without kvmvapic. There are these
> error messages though:
> (qemu) Invalid write to memory region kvm-pic
> Invalid write to memory region kvm-pic

Weird, that's a PIO region. And the KVM kernel module should catch all
accesses.

> 
> Here's 'info mtree' output, kvmvapic-rom line may be interesting:
> 
> memory
> 0000000000000000-7ffffffffffffffe (prio 0, RW): system
>   0000000000000000-000000000fffffff (prio 0, RW): alias ram-below-4g
> @pc.ram 0000000000000000-000000000fffffff
>   00000000000a0000-00000000000bffff (prio 1, RW): alias smram-region
> @pci 00000000000a0000-00000000000bffff
>   00000000000c0000-00000000000c3fff (prio 1, R-): alias pam-rom
> @pc.ram 00000000000c0000-00000000000c3fff
>   00000000000c4000-00000000000c7fff (prio 1, R-): alias pam-rom
> @pc.ram 00000000000c4000-00000000000c7fff
>   00000000000c8000-00000000000cbfff (prio 1, R-): alias pam-rom
> @pc.ram 00000000000c8000-00000000000cbfff
>   00000000000ca000-00000000000ccfff (prio 1000, RW): alias
> kvmvapic-rom @pc.ram 00000000000ca000-00000000000ccfff

Looks ok - it's kind of an option ROM.

Guess I need to dig for a Win2k CD...

Jan



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