[PULL,51/60] kvm: support -overcommit cpu-pm=on|off

diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index e893f72..b921c6f 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -128,6 +128,7 @@  extern bool boot_strict;
 extern uint8_t *boot_splash_filedata;
 extern size_t boot_splash_filedata_size;
 extern bool enable_mlock;
+extern bool enable_cpu_pm;
 extern uint8_t qemu_extra_params_fw[2];
 extern QEMUClockType rtc_clock;
 extern const char *mem_path;
diff --git a/qemu-options.hx b/qemu-options.hx
index 3e45483..81b1e99 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3325,6 +3325,30 @@  mlocking qemu and guest memory can be enabled via @option{mlock=on}
 (enabled by default).
 ETEXI
 
+DEF("overcommit", HAS_ARG, QEMU_OPTION_overcommit,
+    "--overcommit [mem-lock=on|off][cpu-pm=on|off]\n"
+    "                run qemu with overcommit hints\n"
+    "                mem-lock=on|off controls memory lock support (default: off)\n"
+    "                cpu-pm=on|off controls cpu power management (default: off)\n",
+    QEMU_ARCH_ALL)
+STEXI
+@item -overcommit mem-lock=on|off
+@item -overcommit cpu-pm=on|off
+@findex -overcommit
+Run qemu with hints about host resource overcommit. The default is
+to assume that host overcommits all resources.
+
+Locking qemu and guest memory can be enabled via @option{mem-lock=on} (disabled
+by default).  This works when host memory is not overcommitted and reduces the
+worst-case latency for guest.  This is equivalent to @option{realtime}.
+
+Guest ability to manage power state of host cpus (increasing latency for other
+processes on the same host cpu, but decreasing latency for guest) can be
+enabled via @option{cpu-pm=on} (disabled by default).  This works best when
+host CPU is not overcommitted. When used, host estimates of CPU cycle and power
+utilization will be incorrect, not taking into account guest idle time.
+ETEXI
+
 DEF("gdb", HAS_ARG, QEMU_OPTION_gdb, \
     "-gdb dev        wait for gdb connection on 'dev'\n", QEMU_ARCH_ALL)
 STEXI
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index 2d174f3..dc991f6 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -1387,6 +1387,29 @@  int kvm_arch_init(MachineState *ms, KVMState *s)
         smram_machine_done.notify = register_smram_listener;
         qemu_add_machine_init_done_notifier(&smram_machine_done);
     }
+
+    if (enable_cpu_pm) {
+        int disable_exits = kvm_check_extension(s, KVM_CAP_X86_DISABLE_EXITS);
+        int ret;
+
+/* Work around for kernel header with a typo. TODO: fix header and drop. */
+#if defined(KVM_X86_DISABLE_EXITS_HTL) && !defined(KVM_X86_DISABLE_EXITS_HLT)
+#define KVM_X86_DISABLE_EXITS_HLT KVM_X86_DISABLE_EXITS_HTL
+#endif
+        if (disable_exits) {
+            disable_exits &= (KVM_X86_DISABLE_EXITS_MWAIT |
+                              KVM_X86_DISABLE_EXITS_HLT |
+                              KVM_X86_DISABLE_EXITS_PAUSE);
+        }
+
+        ret = kvm_vm_enable_cap(s, KVM_CAP_X86_DISABLE_EXITS, 0,
+                                disable_exits);
+        if (ret < 0) {
+            error_report("kvm: guest stopping CPU not supported: %s",
+                         strerror(-ret));
+        }
+    }
+
     return 0;
 }
 
diff --git a/vl.c b/vl.c
index 7c9f19a..ef6cfce 100644
--- a/vl.c
+++ b/vl.c
@@ -142,6 +142,7 @@  ram_addr_t ram_size;
 const char *mem_path = NULL;
 int mem_prealloc = 0; /* force preallocation of physical target memory */
 bool enable_mlock = false;
+bool enable_cpu_pm = false;
 int nb_nics;
 NICInfo nd_table[MAX_NICS];
 int autostart;
@@ -390,6 +391,22 @@  static QemuOptsList qemu_realtime_opts = {
     },
 };
 
+static QemuOptsList qemu_overcommit_opts = {
+    .name = "overcommit",
+    .head = QTAILQ_HEAD_INITIALIZER(qemu_overcommit_opts.head),
+    .desc = {
+        {
+            .name = "mem-lock",
+            .type = QEMU_OPT_BOOL,
+        },
+        {
+            .name = "cpu-pm",
+            .type = QEMU_OPT_BOOL,
+        },
+        { /* end of list */ }
+    },
+};
+
 static QemuOptsList qemu_msg_opts = {
     .name = "msg",
     .head = QTAILQ_HEAD_INITIALIZER(qemu_msg_opts.head),
@@ -3906,7 +3923,20 @@  int main(int argc, char **argv, char **envp)
                 if (!opts) {
                     exit(1);
                 }
-                enable_mlock = qemu_opt_get_bool(opts, "mlock", true);
+                /* Don't override the -overcommit option if set */
+                enable_mlock = enable_mlock ||
+                    qemu_opt_get_bool(opts, "mlock", true);
+                break;
+            case QEMU_OPTION_overcommit:
+                opts = qemu_opts_parse_noisily(qemu_find_opts("overcommit"),
+                                               optarg, false);
+                if (!opts) {
+                    exit(1);
+                }
+                /* Don't override the -realtime option if set */
+                enable_mlock = enable_mlock ||
+                    qemu_opt_get_bool(opts, "mem-lock", false);
+                enable_cpu_pm = qemu_opt_get_bool(opts, "cpu-pm", false);
                 break;
             case QEMU_OPTION_msg:
                 opts = qemu_opts_parse_noisily(qemu_find_opts("msg"), optarg,