Commit 2266d443 authored by Michael S. Tsirkin's avatar Michael S. Tsirkin Committed by Paolo Bonzini
Browse files

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: default avatarMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: default avatarEduardo Habkost <ehabkost@redhat.com>
Message-Id: <20180622192148.178309-3-mst@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 6f131f13

accel/tcg/user-exec-stub.c

+3 −0
Original line number Diff line number Diff line
@@ -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)

{

target/i386/cpu.c

+22 −10
Original line number Diff line number Diff line
@@ -3959,11 +3959,11 @@ 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 */
@@ -4804,13 +4804,25 @@ 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()) {

    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;

target/i386/cpu.h

+9 −0
Original line number Diff line number Diff line
@@ -1382,6 +1382,15 @@ 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 */

    uint32_t filtered_features[FEATURE_WORDS];

target/i386/kvm.c

+9 −0
Original line number Diff line number Diff line
@@ -366,6 +366,15 @@ 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) {