CMPS and SCAS instructions are evaluated in the wrong order. For reference (of CMPS), see http://www.fermimn.gov.it/linux/quarta/x86/cmps.htm : "Note that the direction of subtraction for CMPS is [SI] - [DI] or [ESI] - [EDI]. The left operand (SI or ESI) is the source and the right operand (DI or EDI) is the destination. This is the reverse of the usual Intel convention in which the left operand is the destination and the right operand is the source." Introducing em_cmp_r for this matter that performs comparison in reverse order using fastop infrastructure to avoid a wrapper function. Signed-off-by: Nadav Amit <namit@xxxxxxxxxxxxxxxxx> --- arch/x86/kvm/emulate.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index f1484bb..9dfd286 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -380,6 +380,15 @@ static int fastop(struct x86_emulate_ctxt *ctxt, void (*fop)(struct fastop *)); ON64(FOP2E(op##q, rax, cl)) \ FOP_END +/* 2 operand, src and dest are reversed */ +#define FASTOP2R(op, name) \ + FOP_START(name) \ + FOP2E(op##b, dl, al) \ + FOP2E(op##w, dx, ax) \ + FOP2E(op##l, edx, eax) \ + ON64(FOP2E(op##q, rdx, rax)) \ + FOP_END + #define FOP3E(op, dst, src, src2) \ FOP_ALIGN #op " %" #src2 ", %" #src ", %" #dst " \n\t" FOP_RET @@ -890,6 +899,8 @@ FASTOP2W(btc); FASTOP2(xadd); +FASTOP2R(cmp, cmp_r); + static u8 test_cc(unsigned int condition, unsigned long flags) { u8 rc; @@ -3973,12 +3984,12 @@ static const struct opcode opcode_table[256] = { I2bv(DstAcc | SrcMem | Mov | MemAbs, em_mov), I2bv(DstMem | SrcAcc | Mov | MemAbs | PageTable, em_mov), I2bv(SrcSI | DstDI | Mov | String, em_mov), - F2bv(SrcSI | DstDI | String | NoWrite, em_cmp), + F2bv(SrcSI | DstDI | String | NoWrite, em_cmp_r), /* 0xA8 - 0xAF */ F2bv(DstAcc | SrcImm | NoWrite, em_test), I2bv(SrcAcc | DstDI | Mov | String, em_mov), I2bv(SrcSI | DstAcc | Mov | String, em_mov), - F2bv(SrcAcc | DstDI | String | NoWrite, em_cmp), + F2bv(SrcAcc | DstDI | String | NoWrite, em_cmp_r), /* 0xB0 - 0xB7 */ X8(I(ByteOp | DstReg | SrcImm | Mov, em_mov)), /* 0xB8 - 0xBF */ -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
