Re: [PATCH 01/62] kvm: Make pi_enable_wakeup_handler() easier to analyze

[Sean Christopherson]

For the scope, please use:

   KVM: VMX:

On Mon, Feb 23, 2026, Bart Van Assche wrote:
> The Clang thread-safety analyzer does not support comparing expressions
> that use per_cpu(). Hence introduce a new local variable to capture the
> address of a per-cpu spinlock. This patch prepares for enabling the
> Clang thread-safety analyzer.
> 
> Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: kvm@xxxxxxxxxxxxxxx
> Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
> ---
>  arch/x86/kvm/vmx/posted_intr.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
> index 4a6d9a17da23..f8711b7b85a8 100644
> --- a/arch/x86/kvm/vmx/posted_intr.c
> +++ b/arch/x86/kvm/vmx/posted_intr.c
> @@ -164,6 +164,7 @@ static void pi_enable_wakeup_handler(struct kvm_vcpu *vcpu)
>  	struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
>  	struct vcpu_vt *vt = to_vt(vcpu);
>  	struct pi_desc old, new;
> +	raw_spinlock_t *wakeup_lock;
>  
>  	lockdep_assert_irqs_disabled();
>  
> @@ -179,11 +180,11 @@ static void pi_enable_wakeup_handler(struct kvm_vcpu *vcpu)
>  	 * entirety of the sched_out critical section, i.e. the wakeup handler
>  	 * can't run while the scheduler locks are held.
>  	 */
> -	raw_spin_lock_nested(&per_cpu(wakeup_vcpus_on_cpu_lock, vcpu->cpu),
> -			     PI_LOCK_SCHED_OUT);
> +	wakeup_lock = &per_cpu(wakeup_vcpus_on_cpu_lock, vcpu->cpu);

Addressing this piecemeal doesn't seem maintainable in the long term.  The odds
of unintentionally regressing the coverage with a cleanup are rather high.  Or
we'll end up with confused and/or grumpy developers because they're required to
write code in a very specific way because of what are effectively shortcomings
in the compiler.

> +	raw_spin_lock_nested(wakeup_lock, PI_LOCK_SCHED_OUT);
>  	list_add_tail(&vt->pi_wakeup_list,
>  		      &per_cpu(wakeup_vcpus_on_cpu, vcpu->cpu));
> -	raw_spin_unlock(&per_cpu(wakeup_vcpus_on_cpu_lock, vcpu->cpu));
> +	raw_spin_unlock(wakeup_lock);
>  
>  	WARN(pi_test_sn(pi_desc), "PI descriptor SN field set before blocking");
>