Commit b586c5d2 authored by Maxim Levitsky's avatar Maxim Levitsky Committed by Paolo Bonzini
Browse files

KVM: arm64: use kvm_trylock_all_vcpus when locking all vCPUs 



Use kvm_trylock_all_vcpus instead of a custom implementation when locking
all vCPUs of a VM, to avoid triggering a lockdep warning, in the case in
which the VM is configured to have more than MAX_LOCK_DEPTH vCPUs.

This fixes the following false lockdep warning:

[  328.171264] BUG: MAX_LOCK_DEPTH too low!
[  328.175227] turning off the locking correctness validator.
[  328.180726] Please attach the output of /proc/lock_stat to the bug report
[  328.187531] depth: 48  max: 48!
[  328.190678] 48 locks held by qemu-kvm/11664:
[  328.194957]  #0: ffff800086de5ba0 (&kvm->lock){+.+.}-{3:3}, at: kvm_ioctl_create_device+0x174/0x5b0
[  328.204048]  #1: ffff0800e78800b8 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0
[  328.212521]  #2: ffff07ffeee51e98 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0
[  328.220991]  #3: ffff0800dc7d80b8 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0
[  328.229463]  #4: ffff07ffe0c980b8 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0
[  328.237934]  #5: ffff0800a3883c78 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0
[  328.246405]  #6: ffff07fffbe480b8 (&vcpu->mutex){+.+.}-{3:3}, at: lock_all_vcpus+0x16c/0x2a0

Suggested-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarMaxim Levitsky <mlevitsk@redhat.com>
Acked-by: default avatarMarc Zyngier <maz@kernel.org>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Message-ID: <20250512180407.659015-6-mlevitsk@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent c560bc92

arch/arm64/include/asm/kvm_host.h

+0 −3
Original line number Diff line number Diff line
@@ -1320,9 +1320,6 @@ int __init populate_sysreg_config(const struct sys_reg_desc *sr, 
				  unsigned int idx);

int __init populate_nv_trap_config(void);



bool lock_all_vcpus(struct kvm *kvm);

void unlock_all_vcpus(struct kvm *kvm);



void kvm_calculate_traps(struct kvm_vcpu *vcpu);



/* MMIO helpers */

arch/arm64/kvm/arch_timer.c

+2 −2
Original line number Diff line number Diff line
@@ -1766,7 +1766,7 @@ int kvm_vm_ioctl_set_counter_offset(struct kvm *kvm, 


	mutex_lock(&kvm->lock);



	if (lock_all_vcpus(kvm)) {

	if (!kvm_trylock_all_vcpus(kvm)) {

		set_bit(KVM_ARCH_FLAG_VM_COUNTER_OFFSET, &kvm->arch.flags);



		/*
@@ -1778,7 +1778,7 @@ int kvm_vm_ioctl_set_counter_offset(struct kvm *kvm, 
		kvm->arch.timer_data.voffset = offset->counter_offset;

		kvm->arch.timer_data.poffset = offset->counter_offset;



		unlock_all_vcpus(kvm);

		kvm_unlock_all_vcpus(kvm);

	} else {

		ret = -EBUSY;

	}

arch/arm64/kvm/arm.c

+0 −43
Original line number Diff line number Diff line
@@ -1924,49 +1924,6 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) 
	}

}



/* 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-init.c

+2 −2
Original line number Diff line number Diff line
@@ -88,7 +88,7 @@ int kvm_vgic_create(struct kvm *kvm, u32 type) 
	lockdep_assert_held(&kvm->lock);



	ret = -EBUSY;

	if (!lock_all_vcpus(kvm))

	if (kvm_trylock_all_vcpus(kvm))

		return ret;



	mutex_lock(&kvm->arch.config_lock);
@@ -142,7 +142,7 @@ int kvm_vgic_create(struct kvm *kvm, u32 type) 


out_unlock:

	mutex_unlock(&kvm->arch.config_lock);

	unlock_all_vcpus(kvm);

	kvm_unlock_all_vcpus(kvm);

	return ret;

}

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

+4 −4
Original line number Diff line number Diff line
@@ -1971,7 +1971,7 @@ static int vgic_its_attr_regs_access(struct kvm_device *dev, 


	mutex_lock(&dev->kvm->lock);



	if (!lock_all_vcpus(dev->kvm)) {

	if (kvm_trylock_all_vcpus(dev->kvm)) {

		mutex_unlock(&dev->kvm->lock);

		return -EBUSY;

	}
@@ -2006,7 +2006,7 @@ static int vgic_its_attr_regs_access(struct kvm_device *dev, 
	}

out:

	mutex_unlock(&dev->kvm->arch.config_lock);

	unlock_all_vcpus(dev->kvm);

	kvm_unlock_all_vcpus(dev->kvm);

	mutex_unlock(&dev->kvm->lock);

	return ret;

}
@@ -2676,7 +2676,7 @@ static int vgic_its_ctrl(struct kvm *kvm, struct vgic_its *its, u64 attr) 


	mutex_lock(&kvm->lock);



	if (!lock_all_vcpus(kvm)) {

	if (kvm_trylock_all_vcpus(kvm)) {

		mutex_unlock(&kvm->lock);

		return -EBUSY;

	}
@@ -2698,7 +2698,7 @@ static int vgic_its_ctrl(struct kvm *kvm, struct vgic_its *its, u64 attr) 


	mutex_unlock(&its->its_lock);

	mutex_unlock(&kvm->arch.config_lock);

	unlock_all_vcpus(kvm);

	kvm_unlock_all_vcpus(kvm);

	mutex_unlock(&kvm->lock);

	return ret;

}