From 06484a82beb6e712f4ae3b28dd4adbba3b301c69 Mon Sep 17 00:00:00 2001
From: maxv <maxv@NetBSD.org>
Date: Tue, 8 Jan 2019 07:34:22 +0000
Subject: [PATCH] Handle REPN. FreeBSD has a "repn movs", which is a bit
 unusual, but doesn't seem illegal as far as I can tell from the AMD SDM.

With that, I can boot FreeBSD on Qemu+NVMM.
---
 lib/libnvmm/libnvmm_x86.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/lib/libnvmm/libnvmm_x86.c b/lib/libnvmm/libnvmm_x86.c
index f22a4b75ed57..5d466d88d697 100644
--- a/lib/libnvmm/libnvmm_x86.c
+++ b/lib/libnvmm/libnvmm_x86.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: libnvmm_x86.c,v 1.13 2019/01/07 18:13:34 maxv Exp $	*/
+/*	$NetBSD: libnvmm_x86.c,v 1.14 2019/01/08 07:34:22 maxv Exp $	*/
 
 /*
  * Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -2902,11 +2902,6 @@ nvmm_assist_mem(struct nvmm_machine *mach, nvmm_cpuid_t cpuid,
 		return -1;
 	}
 
-	if (__predict_false(instr.legpref.repn)) {
-		errno = ENODEV;
-		return -1;
-	}
-
 	if (instr.opcode->movs) {
 		ret = assist_mem_double(mach, &state, &instr);
 	} else {
@@ -2917,10 +2912,14 @@ nvmm_assist_mem(struct nvmm_machine *mach, nvmm_cpuid_t cpuid,
 		return -1;
 	}
 
-	if (instr.legpref.rep) {
+	if (instr.legpref.rep || instr.legpref.repn) {
 		cnt = rep_dec_apply(&state, instr.address_size);
 		if (cnt == 0) {
 			state.gprs[NVMM_X64_GPR_RIP] += instr.len;
+		} else if (__predict_false(instr.legpref.repn)) {
+			if (state.gprs[NVMM_X64_GPR_RFLAGS] & PSL_Z) {
+				state.gprs[NVMM_X64_GPR_RIP] += instr.len;
+			}
 		}
 	} else {
 		state.gprs[NVMM_X64_GPR_RIP] += instr.len;