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

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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

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