commit 80917728e43e248155c019f743655806b582b099
Author: Avi Kivity <avi@qumranet.com>
Date:   Mon Jul 30 15:56:36 2007 +0300

    KVM: x86 emulator: disable writeback for debug register instructions
    
    These are handled internally by the instruction.
    
    Signed-off-by: Avi Kivity <avi@qumranet.com>

diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index 1a90ba0..2136da5 100644
--- a/drivers/kvm/x86_emulate.c
+++ b/drivers/kvm/x86_emulate.c
@@ -1222,11 +1222,13 @@ twobyte_insn:
 		}
 		break;
 	case 0x21: /* mov from dr to reg */
+		no_wb = 1;
 		if (modrm_mod != 3)
 			goto cannot_emulate;
 		rc = emulator_get_dr(ctxt, modrm_reg, &_regs[modrm_rm]);
 		break;
 	case 0x23: /* mov from reg to dr */
+		no_wb = 1;
 		if (modrm_mod != 3)
 			goto cannot_emulate;
 		rc = emulator_set_dr(ctxt, modrm_reg, _regs[modrm_rm]);