KVM: arm64: Expose {un,}lock_all_vcpus() to the rest of KVM

Being able to lock/unlock all vcpus in one go is a feature that
only the vgic has enjoyed so far. Let's be brave and expose it
to the world.
Reviewed-by: Colton Lewis <coltonlewis@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230330174800.2677007-7-maz@kernel.org

arch/arm64/include/asm/kvm_host.h

@@ -922,6 +922,9 @@ void kvm_reset_sys_regs(struct kvm_vcpu *vcpu);
 
 int __init kvm_sys_reg_table_init(void);
 
+bool lock_all_vcpus(struct kvm *kvm);
+void unlock_all_vcpus(struct kvm *kvm);
+
 /* MMIO helpers */
 void kvm_mmio_write_buf(void *buf, unsigned int len, unsigned long data);
 unsigned long kvm_mmio_read_buf(const void *buf, unsigned int len);

arch/arm64/kvm/arm.c

@@ -1484,6 +1484,49 @@ long kvm_arch_vm_ioctl(struct file *filp,
 	}
 }
 
+/* unlocks vcpus from @vcpu_lock_idx and smaller */
+static void unlock_vcpus(struct kvm *kvm, int vcpu_lock_idx)
+{
+	struct kvm_vcpu *tmp_vcpu;
+
+	for (; vcpu_lock_idx >= 0; vcpu_lock_idx--) {
+		tmp_vcpu = kvm_get_vcpu(kvm, vcpu_lock_idx);
+		mutex_unlock(&tmp_vcpu->mutex);
+	}
+}
+
+void unlock_all_vcpus(struct kvm *kvm)
+{
+	lockdep_assert_held(&kvm->lock);
+
+	unlock_vcpus(kvm, atomic_read(&kvm->online_vcpus) - 1);
+}
+
+/* Returns true if all vcpus were locked, false otherwise */
+bool lock_all_vcpus(struct kvm *kvm)
+{
+	struct kvm_vcpu *tmp_vcpu;
+	unsigned long c;
+
+	lockdep_assert_held(&kvm->lock);
+
+	/*
+	 * Any time a vcpu is in an ioctl (including running), the
+	 * core KVM code tries to grab the vcpu->mutex.
+	 *
+	 * By grabbing the vcpu->mutex of all VCPUs we ensure that no
+	 * other VCPUs can fiddle with the state while we access it.
+	 */
+	kvm_for_each_vcpu(c, tmp_vcpu, kvm) {
+		if (!mutex_trylock(&tmp_vcpu->mutex)) {
+			unlock_vcpus(kvm, c - 1);
+			return false;
+		}
+	}
+
+	return true;
+}
+
 static unsigned long nvhe_percpu_size(void)
 {
 	return (unsigned long)CHOOSE_NVHE_SYM(__per_cpu_end) -

arch/arm64/kvm/vgic/vgic-kvm-device.c

@@ -342,44 +342,6 @@ int vgic_v2_parse_attr(struct kvm_device *dev, struct kvm_device_attr *attr,
 	return 0;
 }
 
-/* unlocks vcpus from @vcpu_lock_idx and smaller */
-static void unlock_vcpus(struct kvm *kvm, int vcpu_lock_idx)
-{
-	struct kvm_vcpu *tmp_vcpu;
-
-	for (; vcpu_lock_idx >= 0; vcpu_lock_idx--) {
-		tmp_vcpu = kvm_get_vcpu(kvm, vcpu_lock_idx);
-		mutex_unlock(&tmp_vcpu->mutex);
-	}
-}
-
-void unlock_all_vcpus(struct kvm *kvm)
-{
-	unlock_vcpus(kvm, atomic_read(&kvm->online_vcpus) - 1);
-}
-
-/* Returns true if all vcpus were locked, false otherwise */
-bool lock_all_vcpus(struct kvm *kvm)
-{
-	struct kvm_vcpu *tmp_vcpu;
-	unsigned long c;
-
-	/*
-	 * Any time a vcpu is run, vcpu_load is called which tries to grab the
-	 * vcpu->mutex.  By grabbing the vcpu->mutex of all VCPUs we ensure
-	 * that no other VCPUs are run and fiddle with the vgic state while we
-	 * access it.
-	 */
-	kvm_for_each_vcpu(c, tmp_vcpu, kvm) {
-		if (!mutex_trylock(&tmp_vcpu->mutex)) {
-			unlock_vcpus(kvm, c - 1);
-			return false;
-		}
-	}
-
-	return true;
-}
-
 /**
  * vgic_v2_attr_regs_access - allows user space to access VGIC v2 state
  *

arch/arm64/kvm/vgic/vgic.h

@@ -273,9 +273,6 @@ int vgic_init(struct kvm *kvm);
 void vgic_debug_init(struct kvm *kvm);
 void vgic_debug_destroy(struct kvm *kvm);
 
-bool lock_all_vcpus(struct kvm *kvm);
-void unlock_all_vcpus(struct kvm *kvm);
-
 static inline int vgic_v3_max_apr_idx(struct kvm_vcpu *vcpu)
 {
 	struct vgic_cpu *cpu_if = &vcpu->arch.vgic_cpu;