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target-i386: Enable x2apic by default on KVM

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When on KVM mode, enable x2apic by default on all CPU models.

Normally we try to keep the CPU model definitions as close as the real
CPUs as possible, but x2apic can be emulated by KVM without host CPU
support for x2apic, and it improves performance by reducing APIC access
overhead. x2apic emulation is available on KVM since 2009 (Linux
2.6.32-rc1), there's no reason for not enabling x2apic by default when
running KVM.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
This commit is contained in:
Eduardo Habkost 2014-02-19 11:58:12 -03:00 committed by Andreas Färber
parent 8fb4f821e9
commit ef02ef5f45
3 changed files with 3 additions and 0 deletions
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1
hw/i386/pc_piix.c
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@ -267,6 +267,7 @@ static void pc_compat_1_7(QEMUMachineInitArgs *args)
smbios_type1_defaults = false;
gigabyte_align = false;
option_rom_has_mr = true;
x86_cpu_compat_disable_kvm_features(FEAT_1_ECX, CPUID_EXT_X2APIC);
}
static void pc_compat_1_6(QEMUMachineInitArgs *args)

1
hw/i386/pc_q35.c
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@ -245,6 +245,7 @@ static void pc_compat_1_7(QEMUMachineInitArgs *args)
smbios_type1_defaults = false;
gigabyte_align = false;
option_rom_has_mr = true;
x86_cpu_compat_disable_kvm_features(FEAT_1_ECX, CPUID_EXT_X2APIC);
}
static void pc_compat_1_6(QEMUMachineInitArgs *args)

1
target-i386/cpu.c
View File

@ -369,6 +369,7 @@ static uint32_t kvm_default_features[FEATURE_WORDS] = {
(1 << KVM_FEATURE_STEAL_TIME) |
(1 << KVM_FEATURE_PV_EOI) |
(1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT),
[FEAT_1_ECX] = CPUID_EXT_X2APIC,
};
void x86_cpu_compat_disable_kvm_features(FeatureWord w, uint32_t features)