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KVM: Pre-allocate cpumasks for kvm_make_all_cpus_request_except()

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Allocating cpumask dynamically in zalloc_cpumask_var() is not ideal.
Allocation is somewhat slow and can (in theory and when CPUMASK_OFFSTACK)
fail. kvm_make_all_cpus_request_except() already disables preemption so
we can use pre-allocated per-cpu cpumasks instead.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210903075141.403071-8-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Vitaly Kuznetsov 2021-09-03 09:51:40 +02:00 committed by Paolo Bonzini
parent 381cecc5d7
commit baff59ccdc
1 changed files with 23 additions and 6 deletions
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29
virt/kvm/kvm_main.c
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@ -155,6 +155,8 @@ static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm);
static unsigned long long kvm_createvm_count;
static unsigned long long kvm_active_vms;
static DEFINE_PER_CPU(cpumask_var_t, cpu_kick_mask);
__weak void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
unsigned long start, unsigned long end)
{
@ -313,14 +315,15 @@ bool kvm_make_all_cpus_request_except(struct kvm *kvm, unsigned int req,
struct kvm_vcpu *except)
{
struct kvm_vcpu *vcpu;
cpumask_var_t cpus;
struct cpumask *cpus;
bool called;
int i, me;
zalloc_cpumask_var(&cpus, GFP_ATOMIC);
me = get_cpu();
cpus = this_cpu_cpumask_var_ptr(cpu_kick_mask);
cpumask_clear(cpus);
kvm_for_each_vcpu(i, vcpu, kvm) {
if (vcpu == except)
continue;
@ -330,7 +333,6 @@ bool kvm_make_all_cpus_request_except(struct kvm *kvm, unsigned int req,
called = kvm_kick_many_cpus(cpus, !!(req & KVM_REQUEST_WAIT));
put_cpu();
free_cpumask_var(cpus);
return called;
}
@ -5560,9 +5562,17 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
goto out_free_3;
}
for_each_possible_cpu(cpu) {
if (!alloc_cpumask_var_node(&per_cpu(cpu_kick_mask, cpu),
GFP_KERNEL, cpu_to_node(cpu))) {
r = -ENOMEM;
goto out_free_4;
}
}
r = kvm_async_pf_init();
if (r)
goto out_free;
goto out_free_5;
kvm_chardev_ops.owner = module;
kvm_vm_fops.owner = module;
@ -5588,7 +5598,10 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
out_unreg:
kvm_async_pf_deinit();
out_free:
out_free_5:
for_each_possible_cpu(cpu)
free_cpumask_var(per_cpu(cpu_kick_mask, cpu));
out_free_4:
kmem_cache_destroy(kvm_vcpu_cache);
out_free_3:
unregister_reboot_notifier(&kvm_reboot_notifier);
@ -5608,8 +5621,12 @@ EXPORT_SYMBOL_GPL(kvm_init);
void kvm_exit(void)
{
int cpu;
debugfs_remove_recursive(kvm_debugfs_dir);
misc_deregister(&kvm_dev);
for_each_possible_cpu(cpu)
free_cpumask_var(per_cpu(cpu_kick_mask, cpu));
kmem_cache_destroy(kvm_vcpu_cache);
kvm_async_pf_deinit();
unregister_syscore_ops(&kvm_syscore_ops);