Re: 2.6.31.5 x86-64 KVM: 'emulation failed (pagetable) rip 7fb49335da7b 66 0f 7f 07'

Avi Kivity
2009-12-02T13:25:18Z

On 11/29/2009 04:23 PM, Avi Kivity wrote:
> On 11/29/2009 03:48 PM, Nix wrote:
>> On 29 Nov 2009, Avi Kivity uttered the following:
>>> 66 0f 7f 07 movdqa %xmm0,(%rdi)
>>>
>>> which we don't emulate.
>> x86-64 glibc 2.10 memset(), perhaps? On SSE-capable platforms that does
>> a whole bunch of
>>
>> L(SSE0QB): movdqa %xmm0,-0xb0(%rdi)
>> L(SSE0QA): movdqa %xmm0,-0xa0(%rdi)
>> L(SSE0Q9): movdqa %xmm0,-0x90(%rdi)
>> L(SSE0Q8): movdqa %xmm0,-0x80(%rdi)
>> L(SSE0Q7): movdqa %xmm0,-0x70(%rdi)
>> L(SSE0Q6): movdqa %xmm0,-0x60(%rdi)
>> L(SSE0Q5): movdqa %xmm0,-0x50(%rdi)
>> L(SSE0Q4): movdqa %xmm0,-0x40(%rdi)
>> L(SSE0Q3): movdqa %xmm0,-0x30(%rdi)
>> L(SSE0Q2): movdqa %xmm0,-0x20(%rdi)
>> L(SSE0Q1): movdqa %xmm0,-0x10(%rdi)
>> L(SSE0Q0): retq
>>
>> (multiple blocks of this, catering for alignment, I guess)
>>
>> and x86-64 is always SSE-capable.
>
> Most likely, either this or something similar is called on a userspace
> device driver. Can you check if this is triggered by starting X?
>
> If so, we'll have to emulate this instruction, which will be a bitch.
>

Not just in the emulator, also in the userspace interface. We only
support up to 8 bytes mmio.

Our options in fixing this are:

- extend mmio support to 16 (32? more?) bytes, require new kernel and
new userspace
- use coalesced_mmio for this
- if the mmio happens for a non coalesced mmio region, we flush
immediately
- what if userspace doesn't support coalesced mmio? (unlikely these
days)
- doesn't work for reads (unlikely for 16 byte accesses?)

--
error compiling committee.c: too many arguments to function