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Maxim Levitskybonzini
Maxim Levitsky
authored and
bonzini
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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: Paolo Bonzini <[email protected]> Signed-off-by: Maxim Levitsky <[email protected]> Acked-by: Marc Zyngier <[email protected]> Acked-by: Peter Zijlstra (Intel) <[email protected]> Message-ID: <[email protected]> Signed-off-by: Paolo Bonzini <[email protected]>
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6 files changed

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lines changed

‎arch/arm64/include/asm/kvm_host.h

Lines changed: 0 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1320,9 +1320,6 @@ int __init populate_sysreg_config(const struct sys_reg_desc *sr,
13201320
unsigned int idx);
13211321
int __init populate_nv_trap_config(void);
13221322

1323-
bool lock_all_vcpus(struct kvm *kvm);
1324-
void unlock_all_vcpus(struct kvm *kvm);
1325-
13261323
void kvm_calculate_traps(struct kvm_vcpu *vcpu);
13271324

13281325
/* MMIO helpers */

‎arch/arm64/kvm/arch_timer.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1766,7 +1766,7 @@ int kvm_vm_ioctl_set_counter_offset(struct kvm *kvm,
17661766

17671767
mutex_lock(&kvm->lock);
17681768

1769-
if (lock_all_vcpus(kvm)) {
1769+
if (!kvm_trylock_all_vcpus(kvm)) {
17701770
set_bit(KVM_ARCH_FLAG_VM_COUNTER_OFFSET, &kvm->arch.flags);
17711771

17721772
/*
@@ -1778,7 +1778,7 @@ int kvm_vm_ioctl_set_counter_offset(struct kvm *kvm,
17781778
kvm->arch.timer_data.voffset = offset->counter_offset;
17791779
kvm->arch.timer_data.poffset = offset->counter_offset;
17801780

1781-
unlock_all_vcpus(kvm);
1781+
kvm_unlock_all_vcpus(kvm);
17821782
} else {
17831783
ret = -EBUSY;
17841784
}

‎arch/arm64/kvm/arm.c

Lines changed: 0 additions & 43 deletions
Original file line numberDiff line numberDiff line change
@@ -1924,49 +1924,6 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
19241924
}
19251925
}
19261926

1927-
/* unlocks vcpus from @vcpu_lock_idx and smaller */
1928-
static void unlock_vcpus(struct kvm *kvm, int vcpu_lock_idx)
1929-
{
1930-
struct kvm_vcpu *tmp_vcpu;
1931-
1932-
for (; vcpu_lock_idx >= 0; vcpu_lock_idx--) {
1933-
tmp_vcpu = kvm_get_vcpu(kvm, vcpu_lock_idx);
1934-
mutex_unlock(&tmp_vcpu->mutex);
1935-
}
1936-
}
1937-
1938-
void unlock_all_vcpus(struct kvm *kvm)
1939-
{
1940-
lockdep_assert_held(&kvm->lock);
1941-
1942-
unlock_vcpus(kvm, atomic_read(&kvm->online_vcpus) - 1);
1943-
}
1944-
1945-
/* Returns true if all vcpus were locked, false otherwise */
1946-
bool lock_all_vcpus(struct kvm *kvm)
1947-
{
1948-
struct kvm_vcpu *tmp_vcpu;
1949-
unsigned long c;
1950-
1951-
lockdep_assert_held(&kvm->lock);
1952-
1953-
/*
1954-
* Any time a vcpu is in an ioctl (including running), the
1955-
* core KVM code tries to grab the vcpu->mutex.
1956-
*
1957-
* By grabbing the vcpu->mutex of all VCPUs we ensure that no
1958-
* other VCPUs can fiddle with the state while we access it.
1959-
*/
1960-
kvm_for_each_vcpu(c, tmp_vcpu, kvm) {
1961-
if (!mutex_trylock(&tmp_vcpu->mutex)) {
1962-
unlock_vcpus(kvm, c - 1);
1963-
return false;
1964-
}
1965-
}
1966-
1967-
return true;
1968-
}
1969-
19701927
static unsigned long nvhe_percpu_size(void)
19711928
{
19721929
return (unsigned long)CHOOSE_NVHE_SYM(__per_cpu_end) -

‎arch/arm64/kvm/vgic/vgic-init.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -88,7 +88,7 @@ int kvm_vgic_create(struct kvm *kvm, u32 type)
8888
lockdep_assert_held(&kvm->lock);
8989

9090
ret = -EBUSY;
91-
if (!lock_all_vcpus(kvm))
91+
if (kvm_trylock_all_vcpus(kvm))
9292
return ret;
9393

9494
mutex_lock(&kvm->arch.config_lock);
@@ -142,7 +142,7 @@ int kvm_vgic_create(struct kvm *kvm, u32 type)
142142

143143
out_unlock:
144144
mutex_unlock(&kvm->arch.config_lock);
145-
unlock_all_vcpus(kvm);
145+
kvm_unlock_all_vcpus(kvm);
146146
return ret;
147147
}
148148

‎arch/arm64/kvm/vgic/vgic-its.c

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1971,7 +1971,7 @@ static int vgic_its_attr_regs_access(struct kvm_device *dev,
19711971

19721972
mutex_lock(&dev->kvm->lock);
19731973

1974-
if (!lock_all_vcpus(dev->kvm)) {
1974+
if (kvm_trylock_all_vcpus(dev->kvm)) {
19751975
mutex_unlock(&dev->kvm->lock);
19761976
return -EBUSY;
19771977
}
@@ -2006,7 +2006,7 @@ static int vgic_its_attr_regs_access(struct kvm_device *dev,
20062006
}
20072007
out:
20082008
mutex_unlock(&dev->kvm->arch.config_lock);
2009-
unlock_all_vcpus(dev->kvm);
2009+
kvm_unlock_all_vcpus(dev->kvm);
20102010
mutex_unlock(&dev->kvm->lock);
20112011
return ret;
20122012
}
@@ -2676,7 +2676,7 @@ static int vgic_its_ctrl(struct kvm *kvm, struct vgic_its *its, u64 attr)
26762676

26772677
mutex_lock(&kvm->lock);
26782678

2679-
if (!lock_all_vcpus(kvm)) {
2679+
if (kvm_trylock_all_vcpus(kvm)) {
26802680
mutex_unlock(&kvm->lock);
26812681
return -EBUSY;
26822682
}
@@ -2698,7 +2698,7 @@ static int vgic_its_ctrl(struct kvm *kvm, struct vgic_its *its, u64 attr)
26982698

26992699
mutex_unlock(&its->its_lock);
27002700
mutex_unlock(&kvm->arch.config_lock);
2701-
unlock_all_vcpus(kvm);
2701+
kvm_unlock_all_vcpus(kvm);
27022702
mutex_unlock(&kvm->lock);
27032703
return ret;
27042704
}

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

Lines changed: 6 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -268,15 +268,15 @@ static int vgic_set_common_attr(struct kvm_device *dev,
268268
return -ENXIO;
269269
mutex_lock(&dev->kvm->lock);
270270

271-
if (!lock_all_vcpus(dev->kvm)) {
271+
if (kvm_trylock_all_vcpus(dev->kvm)) {
272272
mutex_unlock(&dev->kvm->lock);
273273
return -EBUSY;
274274
}
275275

276276
mutex_lock(&dev->kvm->arch.config_lock);
277277
r = vgic_v3_save_pending_tables(dev->kvm);
278278
mutex_unlock(&dev->kvm->arch.config_lock);
279-
unlock_all_vcpus(dev->kvm);
279+
kvm_unlock_all_vcpus(dev->kvm);
280280
mutex_unlock(&dev->kvm->lock);
281281
return r;
282282
}
@@ -390,7 +390,7 @@ static int vgic_v2_attr_regs_access(struct kvm_device *dev,
390390

391391
mutex_lock(&dev->kvm->lock);
392392

393-
if (!lock_all_vcpus(dev->kvm)) {
393+
if (kvm_trylock_all_vcpus(dev->kvm)) {
394394
mutex_unlock(&dev->kvm->lock);
395395
return -EBUSY;
396396
}
@@ -415,7 +415,7 @@ static int vgic_v2_attr_regs_access(struct kvm_device *dev,
415415

416416
out:
417417
mutex_unlock(&dev->kvm->arch.config_lock);
418-
unlock_all_vcpus(dev->kvm);
418+
kvm_unlock_all_vcpus(dev->kvm);
419419
mutex_unlock(&dev->kvm->lock);
420420

421421
if (!ret && !is_write)
@@ -554,7 +554,7 @@ static int vgic_v3_attr_regs_access(struct kvm_device *dev,
554554

555555
mutex_lock(&dev->kvm->lock);
556556

557-
if (!lock_all_vcpus(dev->kvm)) {
557+
if (kvm_trylock_all_vcpus(dev->kvm)) {
558558
mutex_unlock(&dev->kvm->lock);
559559
return -EBUSY;
560560
}
@@ -611,7 +611,7 @@ static int vgic_v3_attr_regs_access(struct kvm_device *dev,
611611

612612
out:
613613
mutex_unlock(&dev->kvm->arch.config_lock);
614-
unlock_all_vcpus(dev->kvm);
614+
kvm_unlock_all_vcpus(dev->kvm);
615615
mutex_unlock(&dev->kvm->lock);
616616

617617
if (!ret && uaccess && !is_write) {

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