* [PATCH] KVM: eventfd: Fix false positive RCU usage warning
@ 2022-01-04 2:45 Hou Wenlong
2022-01-04 18:01 ` Sean Christopherson
2022-01-27 6:54 ` [PATCH v2] " Hou Wenlong
0 siblings, 2 replies; 4+ messages in thread
From: Hou Wenlong @ 2022-01-04 2:45 UTC (permalink / raw)
To: kvm; +Cc: Paolo Bonzini, linux-kernel
Fix the following false positive warning:
[ 20.995979] =============================
[ 20.996878] WARNING: suspicious RCU usage
[ 20.997792] 5.16.0-rc4+ #57 Not tainted
[ 20.998651] -----------------------------
[ 20.999544] arch/x86/kvm/../../../virt/kvm/eventfd.c:484 RCU-list traversed in non-reader section!!
[ 21.001490]
[ 21.001490] other info that might help us debug this:
[ 21.001490]
[ 21.003240]
[ 21.003240] rcu_scheduler_active = 2, debug_locks = 1
[ 21.004662] 3 locks held by fc_vcpu 0/330:
[ 21.005573] #0: ffff8884835fc0b0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x88/0x6f0 [kvm]
[ 21.007617] #1: ffffc90004c0bb68 (&kvm->srcu){....}-{0:0}, at: vcpu_enter_guest+0x600/0x1860 [kvm]
[ 21.009627] #2: ffffc90004c0c1d0 (&kvm->irq_srcu){....}-{0:0}, at: kvm_notify_acked_irq+0x36/0x180 [kvm]
[ 21.011732]
[ 21.011732] stack backtrace:
[ 21.012733] CPU: 26 PID: 330 Comm: fc_vcpu 0 Not tainted 5.16.0-rc4+
[ 21.014189] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
[ 21.016565] Call Trace:
[ 21.017105] <TASK>
[ 21.017591] dump_stack_lvl+0x44/0x57
[ 21.018467] kvm_notify_acked_gsi+0x6b/0x70 [kvm]
[ 21.019533] kvm_notify_acked_irq+0x8d/0x180 [kvm]
[ 21.020616] kvm_ioapic_update_eoi+0x92/0x240 [kvm]
[ 21.021736] kvm_apic_set_eoi_accelerated+0x2a/0xe0 [kvm]
[ 21.022968] handle_apic_eoi_induced+0x3d/0x60 [kvm_intel]
[ 21.024168] vmx_handle_exit+0x19c/0x6a0 [kvm_intel]
[ 21.025255] vcpu_enter_guest+0x66e/0x1860 [kvm]
[ 21.026303] ? lock_acquire+0x27f/0x300
[ 21.027166] ? lock_is_held_type+0xdf/0x130
[ 21.028090] ? kvm_arch_vcpu_ioctl_run+0x438/0x7f0 [kvm]
[ 21.029286] ? kvm_arch_vcpu_ioctl_run+0x11a/0x7f0 [kvm]
[ 21.030485] kvm_arch_vcpu_ioctl_run+0x438/0x7f0 [kvm]
[ 21.031647] kvm_vcpu_ioctl+0x38a/0x6f0 [kvm]
[ 21.032647] ? __fget_files+0x156/0x220
[ 21.033522] __x64_sys_ioctl+0x89/0xc0
[ 21.034360] ? syscall_trace_enter.isra.18+0xea/0x260
[ 21.035478] do_syscall_64+0x3a/0x90
[ 21.036259] entry_SYSCALL_64_after_hwframe+0x44/0xae
Since srcu read lock is held, it's a false positive warning.
Use hlist_for_each_entry_srcu() instead of hlist_for_each_entry_rcu()
as it also checkes if the right lock is held.
Signed-off-by: Hou Wenlong <houwenlong93@linux.alibaba.com>
---
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 2ad013b8bde9..59b1dd4a549e 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -463,8 +463,8 @@ 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;
@@ -480,8 +480,8 @@ 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);
}
--
2.31.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] KVM: eventfd: Fix false positive RCU usage warning
2022-01-04 2:45 [PATCH] KVM: eventfd: Fix false positive RCU usage warning Hou Wenlong
@ 2022-01-04 18:01 ` Sean Christopherson
2022-01-27 6:54 ` [PATCH v2] " Hou Wenlong
1 sibling, 0 replies; 4+ messages in thread
From: Sean Christopherson @ 2022-01-04 18:01 UTC (permalink / raw)
To: Hou Wenlong; +Cc: kvm, Paolo Bonzini, linux-kernel
On Tue, Jan 04, 2022, Hou Wenlong wrote:
> Fix the following false positive warning:
> [ 20.995979] =============================
> [ 20.996878] WARNING: suspicious RCU usage
> [ 20.997792] 5.16.0-rc4+ #57 Not tainted
> [ 20.998651] -----------------------------
> [ 20.999544] arch/x86/kvm/../../../virt/kvm/eventfd.c:484 RCU-list traversed in non-reader section!!
> [ 21.001490]
> [ 21.001490] other info that might help us debug this:
> [ 21.001490]
> [ 21.003240]
> [ 21.003240] rcu_scheduler_active = 2, debug_locks = 1
> [ 21.004662] 3 locks held by fc_vcpu 0/330:
> [ 21.005573] #0: ffff8884835fc0b0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x88/0x6f0 [kvm]
> [ 21.007617] #1: ffffc90004c0bb68 (&kvm->srcu){....}-{0:0}, at: vcpu_enter_guest+0x600/0x1860 [kvm]
> [ 21.009627] #2: ffffc90004c0c1d0 (&kvm->irq_srcu){....}-{0:0}, at: kvm_notify_acked_irq+0x36/0x180 [kvm]
> [ 21.011732]
> [ 21.011732] stack backtrace:
> [ 21.012733] CPU: 26 PID: 330 Comm: fc_vcpu 0 Not tainted 5.16.0-rc4+
> [ 21.014189] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
> [ 21.016565] Call Trace:
> [ 21.017105] <TASK>
> [ 21.017591] dump_stack_lvl+0x44/0x57
> [ 21.018467] kvm_notify_acked_gsi+0x6b/0x70 [kvm]
> [ 21.019533] kvm_notify_acked_irq+0x8d/0x180 [kvm]
> [ 21.020616] kvm_ioapic_update_eoi+0x92/0x240 [kvm]
> [ 21.021736] kvm_apic_set_eoi_accelerated+0x2a/0xe0 [kvm]
> [ 21.022968] handle_apic_eoi_induced+0x3d/0x60 [kvm_intel]
> [ 21.024168] vmx_handle_exit+0x19c/0x6a0 [kvm_intel]
> [ 21.025255] vcpu_enter_guest+0x66e/0x1860 [kvm]
> [ 21.026303] ? lock_acquire+0x27f/0x300
> [ 21.027166] ? lock_is_held_type+0xdf/0x130
> [ 21.028090] ? kvm_arch_vcpu_ioctl_run+0x438/0x7f0 [kvm]
> [ 21.029286] ? kvm_arch_vcpu_ioctl_run+0x11a/0x7f0 [kvm]
> [ 21.030485] kvm_arch_vcpu_ioctl_run+0x438/0x7f0 [kvm]
> [ 21.031647] kvm_vcpu_ioctl+0x38a/0x6f0 [kvm]
> [ 21.032647] ? __fget_files+0x156/0x220
> [ 21.033522] __x64_sys_ioctl+0x89/0xc0
> [ 21.034360] ? syscall_trace_enter.isra.18+0xea/0x260
> [ 21.035478] do_syscall_64+0x3a/0x90
> [ 21.036259] entry_SYSCALL_64_after_hwframe+0x44/0xae
For future submissions, please strip the timestamps and the "? " entries, they're
unnecessary noise.
> Since srcu read lock is held, it's a false positive warning.
Stronger phrashing should be used, this makes it sound like SRCU is held by
coincidence, but kvm_unregister_irq_ack_notifier() does synchronize_srcu(&kvm->irq_srcu),
i.e. irq_srcu is indeed intended protection mechansim.
> Use hlist_for_each_entry_srcu() instead of hlist_for_each_entry_rcu()
> as it also checkes if the right lock is held.
>
> Signed-off-by: Hou Wenlong <houwenlong93@linux.alibaba.com>
Changelog nits aside,
Reviewed-by: Sean Christopherson <seanjc@google.com>
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH v2] KVM: eventfd: Fix false positive RCU usage warning
2022-01-04 2:45 [PATCH] KVM: eventfd: Fix false positive RCU usage warning Hou Wenlong
2022-01-04 18:01 ` Sean Christopherson
@ 2022-01-27 6:54 ` Hou Wenlong
2022-01-27 12:08 ` Paolo Bonzini
1 sibling, 1 reply; 4+ messages in thread
From: Hou Wenlong @ 2022-01-27 6:54 UTC (permalink / raw)
To: kvm; +Cc: Hou Wenlong, Sean Christopherson, Paolo Bonzini, linux-kernel
From: Hou Wenlong <houwenlong93@linux.alibaba.com>
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),
i.e. kvm->irq_ack_notifier_list is protected by kvm->irq_srcu. And
kvm->irq_srcu SRCU read lock is held in kvm_notify_acked_irq(), it's
a false positive warning. Use hlist_for_each_entry_srcu() instead of
hlist_for_each_entry_rcu() as it also checkes if the right lock is held.
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Hou Wenlong <houwenlong93@linux.alibaba.com>
---
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 2ad013b8bde9..59b1dd4a549e 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -463,8 +463,8 @@ 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;
@@ -480,8 +480,8 @@ 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);
}
--
2.31.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2] KVM: eventfd: Fix false positive RCU usage warning
2022-01-27 6:54 ` [PATCH v2] " Hou Wenlong
@ 2022-01-27 12:08 ` Paolo Bonzini
0 siblings, 0 replies; 4+ messages in thread
From: Paolo Bonzini @ 2022-01-27 12:08 UTC (permalink / raw)
To: Hou Wenlong, kvm; +Cc: Hou Wenlong, Sean Christopherson, linux-kernel
On 1/27/22 07:54, Hou Wenlong wrote:
> From: Hou Wenlong <houwenlong93@linux.alibaba.com>
>
> 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),
> i.e. kvm->irq_ack_notifier_list is protected by kvm->irq_srcu. And
> kvm->irq_srcu SRCU read lock is held in kvm_notify_acked_irq(), it's
> a false positive warning. Use hlist_for_each_entry_srcu() instead of
> hlist_for_each_entry_rcu() as it also checkes if the right lock is held.
>
> Reviewed-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Hou Wenlong <houwenlong93@linux.alibaba.com>
> ---
> 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 2ad013b8bde9..59b1dd4a549e 100644
> --- a/virt/kvm/eventfd.c
> +++ b/virt/kvm/eventfd.c
> @@ -463,8 +463,8 @@ 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;
> @@ -480,8 +480,8 @@ 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);
> }
> --
> 2.31.1
>
Queued, thanks.
Paolo
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-01-27 12:08 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2022-01-04 2:45 [PATCH] KVM: eventfd: Fix false positive RCU usage warning Hou Wenlong
2022-01-04 18:01 ` Sean Christopherson
2022-01-27 6:54 ` [PATCH v2] " Hou Wenlong
2022-01-27 12:08 ` Paolo Bonzini
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