Messages in this thread Patch in this message | | | From | Yan Zhao <> | Subject | [PATCH] KVM: VMX: fix lockdep warning on posted intr wakeup | Date | Fri, 10 Mar 2023 23:59:55 +0800 |
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Use rcu list to break the possible circular locking dependency reported by lockdep.
path 1, ``sysvec_kvm_posted_intr_wakeup_ipi()`` --> ``pi_wakeup_handler()`` --> ``kvm_vcpu_wake_up()`` --> ``try_to_wake_up()``, the lock sequence is &per_cpu(wakeup_vcpus_on_cpu_lock, cpu) --> &p->pi_lock.
path 2, ``schedule()`` --> ``kvm_sched_out()`` --> ``vmx_vcpu_put()`` --> ``vmx_vcpu_pi_put()`` --> ``pi_enable_wakeup_handler()``, the lock sequence is &rq->__lock --> &per_cpu(wakeup_vcpus_on_cpu_lock, cpu).
path 3, ``task_rq_lock()``, the lock sequence is &p->pi_lock --> &rq->__lock
lockdep report: Chain exists of: &p->pi_lock --> &rq->__lock --> &per_cpu(wakeup_vcpus_on_cpu_lock, cpu)
Possible unsafe locking scenario:
CPU0 CPU1 ---- ---- lock(&per_cpu(wakeup_vcpus_on_cpu_lock, cpu)); lock(&rq->__lock); lock(&per_cpu(wakeup_vcpus_on_cpu_lock, cpu)); lock(&p->pi_lock);
*** DEADLOCK ***
Signed-off-by: Yan Zhao <yan.y.zhao@intel.com> --- arch/x86/kvm/vmx/posted_intr.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c index 94c38bea60e7..e3ffc45c0a7b 100644 --- a/arch/x86/kvm/vmx/posted_intr.c +++ b/arch/x86/kvm/vmx/posted_intr.c @@ -90,7 +90,7 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu) */ if (pi_desc->nv == POSTED_INTR_WAKEUP_VECTOR) { raw_spin_lock(&per_cpu(wakeup_vcpus_on_cpu_lock, vcpu->cpu)); - list_del(&vmx->pi_wakeup_list); + list_del_rcu(&vmx->pi_wakeup_list); raw_spin_unlock(&per_cpu(wakeup_vcpus_on_cpu_lock, vcpu->cpu)); } @@ -153,7 +153,7 @@ static void pi_enable_wakeup_handler(struct kvm_vcpu *vcpu) local_irq_save(flags); raw_spin_lock(&per_cpu(wakeup_vcpus_on_cpu_lock, vcpu->cpu)); - list_add_tail(&vmx->pi_wakeup_list, + list_add_tail_rcu(&vmx->pi_wakeup_list, &per_cpu(wakeup_vcpus_on_cpu, vcpu->cpu)); raw_spin_unlock(&per_cpu(wakeup_vcpus_on_cpu_lock, vcpu->cpu)); @@ -219,16 +219,14 @@ void pi_wakeup_handler(void) { int cpu = smp_processor_id(); struct list_head *wakeup_list = &per_cpu(wakeup_vcpus_on_cpu, cpu); - raw_spinlock_t *spinlock = &per_cpu(wakeup_vcpus_on_cpu_lock, cpu); struct vcpu_vmx *vmx; - raw_spin_lock(spinlock); - list_for_each_entry(vmx, wakeup_list, pi_wakeup_list) { - + rcu_read_lock(); + list_for_each_entry_rcu(vmx, wakeup_list, pi_wakeup_list) { if (pi_test_on(&vmx->pi_desc)) kvm_vcpu_wake_up(&vmx->vcpu); } - raw_spin_unlock(spinlock); + rcu_read_unlock(); } void __init pi_init_cpu(int cpu) base-commit: 89400df96a7570b651404bbc3b7afe627c52a192 -- 2.17.1
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