diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index ae24b75..b500419 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -440,7 +440,7 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
         .cpuid_eax = 0xd,
         .cpuid_needs_ecx = true, .cpuid_ecx = 1,
         .cpuid_reg = R_EAX,
-        .tcg_features = CPUID_XSAVE_XGETBV1,
+        .tcg_features = CPUID_XSAVE_XSAVEOPT | CPUID_XSAVE_XGETBV1,
     },
     [FEAT_6_EAX] = {
         .feat_names = cpuid_6_feature_name,
diff --git a/target-i386/fpu_helper.c b/target-i386/fpu_helper.c
index 568a9b8..a8512ea 100644
--- a/target-i386/fpu_helper.c
+++ b/target-i386/fpu_helper.c
@@ -1196,7 +1196,8 @@ static uint64_t get_xinuse(CPUX86State *env)
     return -1;
 }
 
-void helper_xsave(CPUX86State *env, target_ulong ptr, uint64_t rfbm)
+static void do_xsave(CPUX86State *env, target_ulong ptr,
+                     uint64_t rfbm, uint64_t inuse, uint64_t opt, uintptr_t retaddr)
 {
     uint64_t old_bv, new_bv;
 
@@ -1207,19 +1208,34 @@ void helper_xsave(CPUX86State *env, target_ulong ptr, uint64_t rfbm)
 
     /* Never save anything not enabled by XCR0.  */
     rfbm &= env->xcr0;
+    opt &= rfbm;
 
-    if (rfbm & XSTATE_FP) {
-        do_xsave_fpu(env, ptr, GETPC());
+    if (opt & XSTATE_FP) {
+        do_xsave_fpu(env, ptr, retaddr);
     }
     if (rfbm & XSTATE_SSE) {
-        do_xsave_mxcsr(env, ptr, GETPC());
-        do_xsave_sse(env, ptr, GETPC());
+        /* Note that saving MXCSR is not suppressed by XSAVEOPT.  */
+        do_xsave_mxcsr(env, ptr, retaddr);
+    }
+    if (opt & XSTATE_SSE) {
+        do_xsave_sse(env, ptr, retaddr);
     }
 
     /* Update the XSTATE_BV field.  */
-    old_bv = cpu_ldq_data_ra(env, ptr + 512, GETPC());
-    new_bv = (old_bv & ~rfbm) | (get_xinuse(env) & rfbm);
-    cpu_stq_data_ra(env, ptr + 512, new_bv, GETPC());
+    old_bv = cpu_ldq_data_ra(env, ptr + 512, retaddr);
+    new_bv = (old_bv & ~rfbm) | (inuse & rfbm);
+    cpu_stq_data_ra(env, ptr + 512, new_bv, retaddr);
+}
+
+void helper_xsave(CPUX86State *env, target_ulong ptr, uint64_t rfbm)
+{
+    do_xsave(env, ptr, rfbm, get_xinuse(env), -1, GETPC());
+}
+
+void helper_xsaveopt(CPUX86State *env, target_ulong ptr, uint64_t rfbm)
+{
+    uint64_t inuse = get_xinuse(env);
+    do_xsave(env, ptr, rfbm, inuse, inuse, GETPC());
 }
 
 static void do_xrstor_fpu(CPUX86State *env, target_ulong ptr, uintptr_t retaddr)
@@ -1349,8 +1365,10 @@ uint64_t helper_xgetbv(CPUX86State *env, uint32_t ecx)
     case 0:
         return env->xcr0;
     case 1:
-        /* FIXME: #GP if !CPUID.(EAX=0DH,ECX=1):EAX.XG1[bit 2].  */
-        return env->xcr0 & get_xinuse(env);
+        if (env->features[FEAT_XSAVE] & CPUID_XSAVE_XGETBV1) {
+            return env->xcr0 & get_xinuse(env);
+        }
+        break;
     }
     raise_exception_err_ra(env, EXCP0D_GPF, 0, GETPC());
 }
diff --git a/target-i386/helper.h b/target-i386/helper.h
index 9dfc735..9a83955 100644
--- a/target-i386/helper.h
+++ b/target-i386/helper.h
@@ -188,6 +188,7 @@ DEF_HELPER_3(frstor, void, env, tl, int)
 DEF_HELPER_FLAGS_2(fxsave, TCG_CALL_NO_WG, void, env, tl)
 DEF_HELPER_FLAGS_2(fxrstor, TCG_CALL_NO_WG, void, env, tl)
 DEF_HELPER_FLAGS_3(xsave, TCG_CALL_NO_WG, void, env, tl, i64)
+DEF_HELPER_FLAGS_3(xsaveopt, TCG_CALL_NO_WG, void, env, tl, i64)
 DEF_HELPER_FLAGS_3(xrstor, TCG_CALL_NO_WG, void, env, tl, i64)
 DEF_HELPER_FLAGS_2(xgetbv, TCG_CALL_NO_WG, i64, env, i32)
 DEF_HELPER_FLAGS_3(xsetbv, TCG_CALL_NO_WG, void, env, i32, i64)
diff --git a/target-i386/translate.c b/target-i386/translate.c
index 8301270..b84ce3b 100644
--- a/target-i386/translate.c
+++ b/target-i386/translate.c
@@ -127,6 +127,7 @@ typedef struct DisasContext {
     int cpuid_ext2_features;
     int cpuid_ext3_features;
     int cpuid_7_0_ebx_features;
+    int cpuid_xsave_features;
 } DisasContext;
 
 static void gen_eob(DisasContext *s);
@@ -7647,10 +7648,26 @@ static target_ulong disas_insn(CPUX86State *env, DisasContext *s,
                 if (!(s->cpuid_7_0_ebx_features & CPUID_7_0_EBX_CLWB))
                     goto illegal_op;
                 gen_nop_modrm(env, s, modrm);
-            } else {
+            } else if ((modrm & 0xc7) == 0xc0) {
                 /* mfence */
-                if ((modrm & 0xc7) != 0xc0 || !(s->cpuid_features & CPUID_SSE2))
+                if (!(s->cpuid_features & CPUID_SSE2)
+                    || (s->prefix & PREFIX_LOCK)) {
                     goto illegal_op;
+                }
+                /* no-op */
+            } else {
+                /* xsaveopt */
+                if ((s->cpuid_ext_features & CPUID_EXT_XSAVE) == 0
+                    || (s->cpuid_xsave_features & CPUID_XSAVE_XSAVEOPT) == 0
+                    || (s->flags & HF_OSXSAVE_MASK) == 0
+                    || (s->prefix & (PREFIX_LOCK | PREFIX_DATA
+                                     | PREFIX_REPZ | PREFIX_REPNZ))) {
+                    goto illegal_op;
+                }
+                gen_lea_modrm(env, s, modrm);
+                tcg_gen_concat_tl_i64(cpu_tmp1_i64, cpu_regs[R_EAX],
+                                      cpu_regs[R_EDX]);
+                gen_helper_xsaveopt(cpu_env, cpu_A0, cpu_tmp1_i64);
             }
             break;
         case 7: /* sfence / clflush / clflushopt / pcommit */
@@ -7859,6 +7876,7 @@ void gen_intermediate_code(CPUX86State *env, TranslationBlock *tb)
     dc->cpuid_ext2_features = env->features[FEAT_8000_0001_EDX];
     dc->cpuid_ext3_features = env->features[FEAT_8000_0001_ECX];
     dc->cpuid_7_0_ebx_features = env->features[FEAT_7_0_EBX];
+    dc->cpuid_xsave_features = env->features[FEAT_XSAVE];
 #ifdef TARGET_X86_64
     dc->lma = (flags >> HF_LMA_SHIFT) & 1;
     dc->code64 = (flags >> HF_CS64_SHIFT) & 1;
