Messages in this thread Patch in this message | | | From | Nadav Amit <> | Subject | [PATCH 4/6] KVM: x86: emulation of dword cmov on long-mode should clear [63:32] | Date | Sun, 15 Jun 2014 16:13:00 +0300 |
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Even if the condition of cmov is not satisfied, bits[63:32] should be cleared. This is clearly stated in Intel's CMOVcc documentation. The solution is to reassign the destination onto itself if the condition is unsatisfied. For that matter the original destination value needs to be read.
Signed-off-by: Nadav Amit <namit@cs.technion.ac.il> --- arch/x86/kvm/emulate.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 0183350..b354531 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -3905,7 +3905,7 @@ static const struct opcode twobyte_table[256] = { N, N, N, N, N, N, N, N, N, N, /* 0x40 - 0x4F */ - X16(D(DstReg | SrcMem | ModRM | Mov)), + X16(D(DstReg | SrcMem | ModRM)), /* 0x50 - 0x5F */ N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, /* 0x60 - 0x6F */ @@ -4799,8 +4799,10 @@ twobyte_insn: ops->get_dr(ctxt, ctxt->modrm_reg, &ctxt->dst.val); break; case 0x40 ... 0x4f: /* cmov */ - ctxt->dst.val = ctxt->dst.orig_val = ctxt->src.val; - if (!test_cc(ctxt->b, ctxt->eflags)) + if (test_cc(ctxt->b, ctxt->eflags)) + ctxt->dst.val = ctxt->src.val; + else if (ctxt->mode != X86EMUL_MODE_PROT64 || + ctxt->op_bytes != 4) ctxt->dst.type = OP_NONE; /* no writeback */ break; case 0x80 ... 0x8f: /* jnz rel, etc*/ -- 1.9.1
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