Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 140bad89 authored by Nadav Amit's avatar Nadav Amit Committed by Paolo Bonzini
Browse files

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: default avatarNadav Amit <namit@cs.technion.ac.il>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 9e8919ae

arch/x86/kvm/emulate.c

+5 −3
Original line number Diff line number Diff line
@@ -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*/