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target/i386: Set maximum APIC ID to KVM prior to vCPU creation

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Specify maximum possible APIC ID assigned for current VM session to KVM
prior to the creation of vCPUs. By this setting, KVM can set up VM-scoped
data structure indexed by the APIC ID, e.g. Posted-Interrupt Descriptor
pointer table to support Intel IPI virtualization, with the most optimal
memory footprint.

It can be achieved by calling KVM_ENABLE_CAP for KVM_CAP_MAX_VCPU_ID
capability once KVM has enabled it. Ignoring the return error if KVM
doesn't support this capability yet.

Signed-off-by: Zeng Guang <guang.zeng@intel.com>
Acked-by: Peter Xu <peterx@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20220825025246.26618-1-guang.zeng@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Zeng Guang 2022-08-25 10:52:46 +08:00 committed by Paolo Bonzini
parent c891c24b1a
commit 19e2a9fb9d
4 changed files with 16 additions and 0 deletions
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4
hw/i386/x86.c
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@ -140,6 +140,10 @@ void x86_cpus_init(X86MachineState *x86ms, int default_cpu_version)
exit(EXIT_FAILURE);
}
if (kvm_enabled()) {
kvm_set_max_apic_id(x86ms->apic_id_limit);
}
possible_cpus = mc->possible_cpu_arch_ids(ms);
for (i = 0; i < ms->smp.cpus; i++) {
x86_cpu_new(x86ms, possible_cpus->cpus[i].arch_id, &error_fatal);

5
target/i386/kvm/kvm-stub.c
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@ -44,3 +44,8 @@ bool kvm_hyperv_expand_features(X86CPU *cpu, Error **errp)
{
abort();
}
void kvm_set_max_apic_id(uint32_t max_apic_id)
{
return;
}

5
target/i386/kvm/kvm.c
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@ -5723,3 +5723,8 @@ void kvm_arch_accel_class_init(ObjectClass *oc)
"Clock cycles without an event window "
"after which a notification VM exit occurs");
}
void kvm_set_max_apic_id(uint32_t max_apic_id)
{
kvm_vm_enable_cap(kvm_state, KVM_CAP_MAX_VCPU_ID, 0, max_apic_id);
}

2
target/i386/kvm/kvm_i386.h
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@ -66,4 +66,6 @@ typedef struct kvm_msr_handlers {
bool kvm_filter_msr(KVMState *s, uint32_t msr, QEMURDMSRHandler *rdmsr,
QEMUWRMSRHandler *wrmsr);
void kvm_set_max_apic_id(uint32_t max_apic_id);
#endif