Il 09/05/2013 11:25, Gleb Natapov ha scritto:
> On Thu, May 09, 2013 at 11:16:07AM +0200, Paolo Bonzini wrote:
>> This is an almost-undocumented instruction available in 32-bit mode.
>> I say "almost" undocumented because AMD documents it in their opcode
>> maps just to say that it is unavailable in 64-bit mode (sections
>> "A.2.1 One-Byte Opcodes" and "B.3 Invalid and Reassigned Instructions
>> in 64-Bit Mode").
>>
>> It is roughly equivalent to "sbb %al, %al" except it does not
>> set the flags. Use fastop to emulate it, but do not use the opcode
>> directly because it would fail if the host is 64-bit!
>>
>> Reported-by: Jun'ichi Nomura <j-nom...@ce.jp.nec.com>
>> Cc: sta...@kernel.org # 3.9
>> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
>> ---
>> arch/x86/kvm/emulate.c | 6 +++++-
>> 1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
>> index 210bb4e..f62d4c8 100644
>> --- a/arch/x86/kvm/emulate.c
>> +++ b/arch/x86/kvm/emulate.c
>> @@ -534,6 +534,9 @@ FOP_SETCC(setle)
>> FOP_SETCC(setnle)
>> FOP_END;
>>
>> +FOP_START(salc) "pushf; sbb %al, %al; popf; ret \n\t"
>
> FOP_RET
Ah, I missed that macro. I was mimicking FOP_SETCC which doesn't use
it. Will resend.
Paolo
>> +FOP_END;
>> +
>> #define __emulate_1op_rax_rdx(ctxt, _op, _suffix, _ex)
>> \
>> do { \
>> unsigned long _tmp; \
>> @@ -3951,7 +3954,8 @@ static const struct opcode opcode_table[256] = {
>> G(Src2One | ByteOp, group2), G(Src2One, group2),
>> G(Src2CL | ByteOp, group2), G(Src2CL, group2),
>> I(DstAcc | SrcImmUByte | No64, em_aam),
>> - I(DstAcc | SrcImmUByte | No64, em_aad), N,
>> + I(DstAcc | SrcImmUByte | No64, em_aad),
>> + F(DstAcc | ByteOp | No64, em_salc),
>> I(DstAcc | SrcXLat | ByteOp, em_mov),
>> /* 0xD8 - 0xDF */
>> N, E(0, &escape_d9), N, E(0, &escape_db), N, E(0, &escape_dd), N, N,
>> --
>> 1.8.1.4
>
> --
> Gleb.
>
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