From: Hou Wenlong houwenlong93@linux.alibaba.com
[ Upstream commit 6a0c61703e3a5d67845a4b275e1d9d7bc1b5aad7 ]
Fix the following false positive warning: ============================= WARNING: suspicious RCU usage 5.16.0-rc4+ #57 Not tainted ----------------------------- arch/x86/kvm/../../../virt/kvm/eventfd.c:484 RCU-list traversed in non-reader section!!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1 3 locks held by fc_vcpu 0/330: #0: ffff8884835fc0b0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x88/0x6f0 [kvm] #1: ffffc90004c0bb68 (&kvm->srcu){....}-{0:0}, at: vcpu_enter_guest+0x600/0x1860 [kvm] #2: ffffc90004c0c1d0 (&kvm->irq_srcu){....}-{0:0}, at: kvm_notify_acked_irq+0x36/0x180 [kvm]
stack backtrace: CPU: 26 PID: 330 Comm: fc_vcpu 0 Not tainted 5.16.0-rc4+ Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x44/0x57 kvm_notify_acked_gsi+0x6b/0x70 [kvm] kvm_notify_acked_irq+0x8d/0x180 [kvm] kvm_ioapic_update_eoi+0x92/0x240 [kvm] kvm_apic_set_eoi_accelerated+0x2a/0xe0 [kvm] handle_apic_eoi_induced+0x3d/0x60 [kvm_intel] vmx_handle_exit+0x19c/0x6a0 [kvm_intel] vcpu_enter_guest+0x66e/0x1860 [kvm] kvm_arch_vcpu_ioctl_run+0x438/0x7f0 [kvm] kvm_vcpu_ioctl+0x38a/0x6f0 [kvm] __x64_sys_ioctl+0x89/0xc0 do_syscall_64+0x3a/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae
Since kvm_unregister_irq_ack_notifier() does synchronize_srcu(&kvm->irq_srcu), kvm->irq_ack_notifier_list is protected by kvm->irq_srcu. In fact, kvm->irq_srcu SRCU read lock is held in kvm_notify_acked_irq(), making it a false positive warning. So use hlist_for_each_entry_srcu() instead of hlist_for_each_entry_rcu().
Reviewed-by: Sean Christopherson seanjc@google.com Signed-off-by: Hou Wenlong houwenlong93@linux.alibaba.com Message-Id: f98bac4f5052bad2c26df9ad50f7019e40434512.1643265976.git.houwenlong.hwl@antgroup.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- virt/kvm/eventfd.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index e996989cd580e..5b874e7ba36fd 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -456,8 +456,8 @@ bool kvm_irq_has_notifier(struct kvm *kvm, unsigned irqchip, unsigned pin) idx = srcu_read_lock(&kvm->irq_srcu); gsi = kvm_irq_map_chip_pin(kvm, irqchip, pin); if (gsi != -1) - hlist_for_each_entry_rcu(kian, &kvm->irq_ack_notifier_list, - link) + hlist_for_each_entry_srcu(kian, &kvm->irq_ack_notifier_list, + link, srcu_read_lock_held(&kvm->irq_srcu)) if (kian->gsi == gsi) { srcu_read_unlock(&kvm->irq_srcu, idx); return true; @@ -473,8 +473,8 @@ void kvm_notify_acked_gsi(struct kvm *kvm, int gsi) { struct kvm_irq_ack_notifier *kian;
- hlist_for_each_entry_rcu(kian, &kvm->irq_ack_notifier_list, - link) + hlist_for_each_entry_srcu(kian, &kvm->irq_ack_notifier_list, + link, srcu_read_lock_held(&kvm->irq_srcu)) if (kian->gsi == gsi) kian->irq_acked(kian); }