Re: Problem with KVM guest switching to x86 long mode

[Pekka Enberg <penberg@cs.helsinki.fi>]

Avi Kivity wrote:
>> Sorry for the delay. Here you go:
>>
>> Page Tables:
>>  pte4: 0000000002403007   pte3: 0000000002404007   pte2: 0000000000000183
> 
> These are all correct.
> 
> The only thing I can think of, is that MAXPHYADDR is small value.  And 
> indeed, if I run it on an ept capable machine (which does the check in 
> hardware, not software), I get
> 
> IO error: OUT port=cf8, size=4, count=1
> KVM exit reason: 2 ("KVM_EXIT_IO")
> Registers:
>  rip: ffffffff813a0d8f   rsp: ffffffff8167bdf8 flags: 0000000000000086
>  rax: 000000008000c300   rbx: 000000000000c000   rcx: 0000000000000000
>  rdx: 0000000000000cf8   rsi: 0000000000000018   rdi: 0000000000000000
>  rbp: ffffffff8167be08   r8:  0000000000000000   r9:  0000000000000000
>  r10: 0000000000000006   r11: 00000000bbceeb20   r12: 0000000000000000
>  r13: 0000000000000000   r14: 0000000000000000   r15: 0000000000000000
>  cr0: 0000000080050033   cr2: 0000000000000000   cr3: 0000000001001000
>  cr4: 00000000000000a0   cr8: 0000000000000000
> 
> So the guest is in long mode, happily trying to access pci config space.
> 
> MAXPHYADDR comes from cpuid 80000008.eax[0:7].  Typical values are 36-40 
> (number of physical address bits supported by the processor).  What 
> value does your guest see?

Ah, nice catch! The host cpuid doesn't seem to support 80000008 at so I 
didn't set it up in the guest either. I now added dummy emulation for it 
and the triple fault is fixed.

Thanks Avi!

			Pekka