From 91ac1f511b0414292d07688c3cb3012bed6e3649 Mon Sep 17 00:00:00 2001

From: "Michael S. Tsirkin" <mst@redhat.com>

Date: Fri, 22 Jun 2018 22:22:05 +0300

Subject: [PATCH 09/11] i386/cpu: make -cpu host support monitor/mwait

When guest CPU PM is enabled, and with -cpu host, expose the host CPU

MWAIT leaf in the CPUID so guest can make good PM decisions.

Note: the result is 100% CPU utilization reported by host as host

no longer knows that the CPU is halted.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>

Message-Id: <20180622192148.178309-3-mst@redhat.com>

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>

---

 accel/tcg/user-exec-stub.c |  3 +++

 target/i386/cpu.c          | 32 ++++++++++++++++++++++----------

 target/i386/cpu.h          |  9 +++++++++

 target/i386/kvm.c          |  9 +++++++++

 4 files changed, 43 insertions(+), 10 deletions(-)

diff --git a/accel/tcg/user-exec-stub.c b/accel/tcg/user-exec-stub.c

index dbcf1ad..a32b449 100644

--- a/accel/tcg/user-exec-stub.c

+++ b/accel/tcg/user-exec-stub.c

@@ -2,6 +2,9 @@

 #include "qemu-common.h"

 #include "qom/cpu.h"

 #include "sysemu/replay.h"

+#include "sysemu/sysemu.h"

+

+bool enable_cpu_pm = false;

 void cpu_resume(CPUState *cpu)

 {

diff --git a/target/i386/cpu.c b/target/i386/cpu.c

index 307b629..87b0502 100644

--- a/target/i386/cpu.c

+++ b/target/i386/cpu.c

@@ -5662,11 +5662,11 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,

         }

         break;

     case 5:

-        /* mwait info: needed for Core compatibility */

-        *eax = 0; /* Smallest monitor-line size in bytes */

-        *ebx = 0; /* Largest monitor-line size in bytes */

-        *ecx = CPUID_MWAIT_EMX | CPUID_MWAIT_IBE;

-        *edx = 0;

+        /* MONITOR/MWAIT Leaf */

+        *eax = cpu->mwait.eax; /* Smallest monitor-line size in bytes */

+        *ebx = cpu->mwait.ebx; /* Largest monitor-line size in bytes */

+        *ecx = cpu->mwait.ecx; /* flags */

+        *edx = cpu->mwait.edx; /* mwait substates */

         break;

     case 6:

         /* Thermal and Power Leaf */

@@ -6521,13 +6521,25 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)

     Error *local_err = NULL;

     static bool ht_warned;

-    if (xcc->host_cpuid_required && !accel_uses_host_cpuid()) {

-        char *name = x86_cpu_class_get_model_name(xcc);

-        error_setg(&local_err, "CPU model '%s' requires KVM", name);

-        g_free(name);

-        goto out;

+    if (xcc->host_cpuid_required) {

+        if (!accel_uses_host_cpuid()) {

+            char *name = x86_cpu_class_get_model_name(xcc);

+            error_setg(&local_err, "CPU model '%s' requires KVM", name);

+            g_free(name);

+            goto out;

+        }

+

+        if (enable_cpu_pm) {

+            host_cpuid(5, 0, &cpu->mwait.eax, &cpu->mwait.ebx,

+                       &cpu->mwait.ecx, &cpu->mwait.edx);

+            env->features[FEAT_1_ECX] |= CPUID_EXT_MONITOR;

+        }

     }

+    /* mwait extended info: needed for Core compatibility */

+    /* We always wake on interrupt even if host does not have the capability */

+    cpu->mwait.ecx |= CPUID_MWAIT_EMX | CPUID_MWAIT_IBE;

+

     if (cpu->apic_id == UNASSIGNED_APIC_ID) {

         error_setg(errp, "apic-id property was not initialized properly");

         return;

diff --git a/target/i386/cpu.h b/target/i386/cpu.h

index d33fa8d..7ab8ee9 100644

--- a/target/i386/cpu.h

+++ b/target/i386/cpu.h

@@ -1564,6 +1564,15 @@ struct X86CPU {

     /* if true the CPUID code directly forward host cache leaves to the guest */

     bool cache_info_passthrough;

+    /* if true the CPUID code directly forwards

+     * host monitor/mwait leaves to the guest */

+    struct {

+        uint32_t eax;

+        uint32_t ebx;

+        uint32_t ecx;

+        uint32_t edx;

+    } mwait;

+

     /* Features that were filtered out because of missing host capabilities */

     FeatureWordArray filtered_features;

diff --git a/target/i386/kvm.c b/target/i386/kvm.c

index 879c3e0..ffd01f0 100644

--- a/target/i386/kvm.c

+++ b/target/i386/kvm.c

@@ -377,6 +377,15 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function,

         if (!kvm_irqchip_in_kernel()) {

             ret &= ~CPUID_EXT_X2APIC;

         }

+

+        if (enable_cpu_pm) {

+            int disable_exits = kvm_check_extension(s,

+                                                    KVM_CAP_X86_DISABLE_EXITS);

+

+            if (disable_exits & KVM_X86_DISABLE_EXITS_MWAIT) {

+                ret |= CPUID_EXT_MONITOR;

+            }

+        }

     } else if (function == 6 && reg == R_EAX) {

         ret |= CPUID_6_EAX_ARAT; /* safe to allow because of emulated APIC */

     } else if (function == 7 && index == 0 && reg == R_EBX) {

-- 

1.8.3.1