KVM: introduce kvm_make_vcpus_request_mask() API

Hyper-V style PV TLB flush hypercalls inmplementation will use this API.
To avoid memory allocation in CONFIG_CPUMASK_OFFSTACK case add
cpumask_var_t argument.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

include/linux/kvm_host.h

@@ -730,6 +730,9 @@ void kvm_put_guest_fpu(struct kvm_vcpu *vcpu);
 
 void kvm_flush_remote_tlbs(struct kvm *kvm);
 void kvm_reload_remote_mmus(struct kvm *kvm);
+
+bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req,
+				 unsigned long *vcpu_bitmap, cpumask_var_t tmp);
 bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req);
 
 long kvm_arch_dev_ioctl(struct file *filp,

virt/kvm/kvm_main.c

@@ -203,29 +203,47 @@ static inline bool kvm_kick_many_cpus(const struct cpumask *cpus, bool wait)
 	return true;
 }
 
-bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
+bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req,
+				 unsigned long *vcpu_bitmap, cpumask_var_t tmp)
 {
 	int i, cpu, me;
-	cpumask_var_t cpus;
-	bool called;
 	struct kvm_vcpu *vcpu;
-
-	zalloc_cpumask_var(&cpus, GFP_ATOMIC);
+	bool called;
 
 	me = get_cpu();
+
 	kvm_for_each_vcpu(i, vcpu, kvm) {
+		if (!test_bit(i, vcpu_bitmap))
+			continue;
+
 		kvm_make_request(req, vcpu);
 		cpu = vcpu->cpu;
 
 		if (!(req & KVM_REQUEST_NO_WAKEUP) && kvm_vcpu_wake_up(vcpu))
 			continue;
 
-		if (cpus != NULL && cpu != -1 && cpu != me &&
+		if (tmp != NULL && cpu != -1 && cpu != me &&
 		    kvm_request_needs_ipi(vcpu, req))
-			__cpumask_set_cpu(cpu, cpus);
+			__cpumask_set_cpu(cpu, tmp);
 	}
-	called = kvm_kick_many_cpus(cpus, !!(req & KVM_REQUEST_WAIT));
+
+	called = kvm_kick_many_cpus(tmp, !!(req & KVM_REQUEST_WAIT));
 	put_cpu();
+
+	return called;
+}
+
+bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
+{
+	cpumask_var_t cpus;
+	bool called;
+	static unsigned long vcpu_bitmap[BITS_TO_LONGS(KVM_MAX_VCPUS)]
+		= {[0 ... BITS_TO_LONGS(KVM_MAX_VCPUS)-1] = ULONG_MAX};
+
+	zalloc_cpumask_var(&cpus, GFP_ATOMIC);
+
+	called = kvm_make_vcpus_request_mask(kvm, req, vcpu_bitmap, cpus);
+
 	free_cpumask_var(cpus);
 	return called;
 }