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From 91ac1f511b0414292d07688c3cb3012bed6e3649 Mon Sep 17 00:00:00 2001
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From: "Michael S. Tsirkin" <mst@redhat.com>
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Date: Fri, 22 Jun 2018 22:22:05 +0300
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Subject: [PATCH 09/11] i386/cpu: make -cpu host support monitor/mwait
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When guest CPU PM is enabled, and with -cpu host, expose the host CPU
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MWAIT leaf in the CPUID so guest can make good PM decisions.
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Note: the result is 100% CPU utilization reported by host as host
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no longer knows that the CPU is halted.
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Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
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Message-Id: <20180622192148.178309-3-mst@redhat.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 accel/tcg/user-exec-stub.c |  3 +++
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 target/i386/cpu.c          | 32 ++++++++++++++++++++++----------
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 target/i386/cpu.h          |  9 +++++++++
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 target/i386/kvm.c          |  9 +++++++++
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 4 files changed, 43 insertions(+), 10 deletions(-)
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diff --git a/accel/tcg/user-exec-stub.c b/accel/tcg/user-exec-stub.c
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index dbcf1ad..a32b449 100644
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--- a/accel/tcg/user-exec-stub.c
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+++ b/accel/tcg/user-exec-stub.c
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@@ -2,6 +2,9 @@
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 #include "qemu-common.h"
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 #include "qom/cpu.h"
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 #include "sysemu/replay.h"
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+#include "sysemu/sysemu.h"
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+
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+bool enable_cpu_pm = false;
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 void cpu_resume(CPUState *cpu)
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 {
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diff --git a/target/i386/cpu.c b/target/i386/cpu.c
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index 307b629..87b0502 100644
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--- a/target/i386/cpu.c
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+++ b/target/i386/cpu.c
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@@ -5662,11 +5662,11 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
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         }
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         break;
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     case 5:
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-        /* mwait info: needed for Core compatibility */
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-        *eax = 0; /* Smallest monitor-line size in bytes */
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-        *ebx = 0; /* Largest monitor-line size in bytes */
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-        *ecx = CPUID_MWAIT_EMX | CPUID_MWAIT_IBE;
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-        *edx = 0;
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+        /* MONITOR/MWAIT Leaf */
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+        *eax = cpu->mwait.eax; /* Smallest monitor-line size in bytes */
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+        *ebx = cpu->mwait.ebx; /* Largest monitor-line size in bytes */
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+        *ecx = cpu->mwait.ecx; /* flags */
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+        *edx = cpu->mwait.edx; /* mwait substates */
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         break;
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     case 6:
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         /* Thermal and Power Leaf */
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@@ -6521,13 +6521,25 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
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     Error *local_err = NULL;
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     static bool ht_warned;
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-    if (xcc->host_cpuid_required && !accel_uses_host_cpuid()) {
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-        char *name = x86_cpu_class_get_model_name(xcc);
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-        error_setg(&local_err, "CPU model '%s' requires KVM", name);
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-        g_free(name);
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-        goto out;
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+    if (xcc->host_cpuid_required) {
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+        if (!accel_uses_host_cpuid()) {
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+            char *name = x86_cpu_class_get_model_name(xcc);
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+            error_setg(&local_err, "CPU model '%s' requires KVM", name);
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+            g_free(name);
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+            goto out;
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+        }
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+
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+        if (enable_cpu_pm) {
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+            host_cpuid(5, 0, &cpu->mwait.eax, &cpu->mwait.ebx,
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+                       &cpu->mwait.ecx, &cpu->mwait.edx);
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+            env->features[FEAT_1_ECX] |= CPUID_EXT_MONITOR;
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+        }
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     }
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+    /* mwait extended info: needed for Core compatibility */
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+    /* We always wake on interrupt even if host does not have the capability */
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+    cpu->mwait.ecx |= CPUID_MWAIT_EMX | CPUID_MWAIT_IBE;
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+
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     if (cpu->apic_id == UNASSIGNED_APIC_ID) {
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         error_setg(errp, "apic-id property was not initialized properly");
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         return;
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diff --git a/target/i386/cpu.h b/target/i386/cpu.h
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index d33fa8d..7ab8ee9 100644
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--- a/target/i386/cpu.h
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+++ b/target/i386/cpu.h
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@@ -1564,6 +1564,15 @@ struct X86CPU {
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     /* if true the CPUID code directly forward host cache leaves to the guest */
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     bool cache_info_passthrough;
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+    /* if true the CPUID code directly forwards
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+     * host monitor/mwait leaves to the guest */
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+    struct {
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+        uint32_t eax;
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+        uint32_t ebx;
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+        uint32_t ecx;
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+        uint32_t edx;
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+    } mwait;
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+
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     /* Features that were filtered out because of missing host capabilities */
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     FeatureWordArray filtered_features;
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diff --git a/target/i386/kvm.c b/target/i386/kvm.c
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index 879c3e0..ffd01f0 100644
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--- a/target/i386/kvm.c
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+++ b/target/i386/kvm.c
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@@ -377,6 +377,15 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function,
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         if (!kvm_irqchip_in_kernel()) {
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             ret &= ~CPUID_EXT_X2APIC;
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         }
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+
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+        if (enable_cpu_pm) {
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+            int disable_exits = kvm_check_extension(s,
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+                                                    KVM_CAP_X86_DISABLE_EXITS);
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+
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+            if (disable_exits & KVM_X86_DISABLE_EXITS_MWAIT) {
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+                ret |= CPUID_EXT_MONITOR;
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+            }
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+        }
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     } else if (function == 6 && reg == R_EAX) {
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         ret |= CPUID_6_EAX_ARAT; /* safe to allow because of emulated APIC */
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     } else if (function == 7 && index == 0 && reg == R_EBX) {
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-- 
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1.8.3.1
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