Re: [PATCH 0/5] Split the emulator: decode & execute

Laurent Vivier
2007-09-14T16:14:38Z

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Avi Kivity wrote:
> Laurent Vivier wrote:
>> These patches split the emulator in two parts: one to decode the
>> instruction,
>> the other to execute it. The decode part is then called only when needed.
>>
>>
>
> Patchset looks good, but fails booting FC6 x86-64 on Intel. It may be a
> merge error (did not apply cleanly due to other changes). I pushed this
> as a 'split-emulator' branch on the kvm.git repository.
>

I think I found the bug (not a merge error...): I just supposed that an
instruction fetch cannot failed.

I wrote:

r = x86_decode_insn(&emulate_ctxt, &emulate_ops);
if (r)
return EMULATE_FAIL;

vcpu->mmio_is_write = 0;
vcpu->pio.string = 0;
r = x86_emulate_insn(&emulate_ctxt, &emulate_ops);
...

It should be:

vcpu->mmio_is_write = 0;
vcpu->pio.string = 0;

r = x86_decode_insn(&emulate_ctxt, &emulate_ops);
if (r == 0) {
r = x86_emulate_insn(&emulate_ctxt, &emulate_ops);
if (vcpu->pio.string)
return EMULATE_DO_MMIO;
}

if ((r || vcpu->mmio_is_write) && run) {
...
}

if (r) {
...
}

Laurent
--
------------- Laurent.Vivier-6ktuUTfB/bM@public.gmane.org --------------
"Software is hard" - Donald Knuth

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