From 140bad89fd25db1aab60f80ed7874e9a9bdbae3b Mon Sep 17 00:00:00 2001 From: Nadav Amit Date: Sun, 15 Jun 2014 16:13:00 +0300 Subject: [PATCH] KVM: x86: emulation of dword cmov on long-mode should clear [63:32] 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 Signed-off-by: Paolo Bonzini --- 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 27ce38693f09..6f09b2e555ef 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -3923,7 +3923,7 @@ 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 */ @@ -4824,8 +4824,10 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt) 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*/