2022-02-15 11:30:12

by Wanpeng Li

Subject: [PATCH] KVM: Fix lockdep false negative during host resume

From: Wanpeng Li <[email protected]>

I saw the below splatting after the host suspended and resumed.

WARNING: CPU: 0 PID: 2943 at kvm/arch/x86/kvm/../../../virt/kvm/kvm_main.c:5531 kvm_resume+0x2c/0x30 [kvm]
CPU: 0 PID: 2943 Comm: step_after_susp Tainted: G W IOE 5.17.0-rc3+ #4
RIP: 0010:kvm_resume+0x2c/0x30 [kvm]
Call Trace:
<TASK>
syscore_resume+0x90/0x340
suspend_devices_and_enter+0xaee/0xe90
pm_suspend.cold+0x36b/0x3c2
state_store+0x82/0xf0
kernfs_fop_write_iter+0x1b6/0x260
new_sync_write+0x258/0x370
vfs_write+0x33f/0x510
ksys_write+0xc9/0x160
do_syscall_64+0x3b/0xc0
entry_SYSCALL_64_after_hwframe+0x44/0xae

lockdep_is_held() can return -1 when lockdep is disabled which triggers
this warning. Let's use lockdep_assert_not_held() which can detect
incorrect calls while holding a lock and it also avoids false negatives
when lockdep is disabled.

Signed-off-by: Wanpeng Li <[email protected]>
---
virt/kvm/kvm_main.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 83c57bcc6eb6..3f861f33bfe0 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -5528,7 +5528,7 @@ static void kvm_resume(void)
{
if (kvm_usage_count) {
#ifdef CONFIG_LOCKDEP
- WARN_ON(lockdep_is_held(&kvm_count_lock));
+ lockdep_assert_not_held(&kvm_count_lock);
#endif
hardware_enable_nolock(NULL);
}
--
2.25.1

2022-02-15 16:53:25

by Sean Christopherson

Subject: Re: [PATCH] KVM: Fix lockdep false negative during host resume

On Tue, Feb 15, 2022, Wanpeng Li wrote:
> From: Wanpeng Li <[email protected]>
>
> I saw the below splatting after the host suspended and resumed.
>
> WARNING: CPU: 0 PID: 2943 at kvm/arch/x86/kvm/../../../virt/kvm/kvm_main.c:5531 kvm_resume+0x2c/0x30 [kvm]
> CPU: 0 PID: 2943 Comm: step_after_susp Tainted: G W IOE 5.17.0-rc3+ #4
> RIP: 0010:kvm_resume+0x2c/0x30 [kvm]
> Call Trace:
> <TASK>
> syscore_resume+0x90/0x340
> suspend_devices_and_enter+0xaee/0xe90
> pm_suspend.cold+0x36b/0x3c2
> state_store+0x82/0xf0
> kernfs_fop_write_iter+0x1b6/0x260
> new_sync_write+0x258/0x370
> vfs_write+0x33f/0x510
> ksys_write+0xc9/0x160
> do_syscall_64+0x3b/0xc0
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> lockdep_is_held() can return -1 when lockdep is disabled which triggers
> this warning. Let's use lockdep_assert_not_held() which can detect
> incorrect calls while holding a lock and it also avoids false negatives
> when lockdep is disabled.
>

Fixes: 2eb06c306a57 ("KVM: Fix spinlock taken warning during host resume")

> Signed-off-by: Wanpeng Li <[email protected]>
> ---
> virt/kvm/kvm_main.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 83c57bcc6eb6..3f861f33bfe0 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -5528,7 +5528,7 @@ static void kvm_resume(void)
> {
> if (kvm_usage_count) {
> #ifdef CONFIG_LOCKDEP

The #ifdef can be dropped, it was added only to omit the WARN_ON.

With that,

Reviewed-by: Sean Christopherson <[email protected]>

> - WARN_ON(lockdep_is_held(&kvm_count_lock));
> + lockdep_assert_not_held(&kvm_count_lock);
> #endif
> hardware_enable_nolock(NULL);
> }
> --
> 2.25.1
>

2022-02-16 00:13:09

by Paolo Bonzini

Subject: Re: [PATCH] KVM: Fix lockdep false negative during host resume

On 2/15/22 17:26, Sean Christopherson wrote:
> Reviewed-by: Sean Christopherson<[email protected]>

Queued with the #ifdef removed, thanks.

Paolo