On Fri, 2021-10-08 at 19:12 -0700, Sean Christopherson wrote:
> Drop sanity checks on the validity of the previous pCPU when handling
> vCPU block/unlock for posted interrupts. Barring a code bug or memory
> corruption, the sanity checks will never fire, and any code bug that does
> trip the WARN is all but guaranteed to completely break posted interrupts,
> i.e. should never get anywhere near production.
>
> This is the first of several steps toward eliminating kvm_vcpu.pre_cpu.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
> arch/x86/kvm/vmx/posted_intr.c | 24 ++++++++++--------------
> 1 file changed, 10 insertions(+), 14 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
> index 67cbe6ab8f66..6c2110d91b06 100644
> --- a/arch/x86/kvm/vmx/posted_intr.c
> +++ b/arch/x86/kvm/vmx/posted_intr.c
> @@ -118,12 +118,10 @@ static void __pi_post_block(struct kvm_vcpu *vcpu)
> } while (cmpxchg64(&pi_desc->control, old.control,
> new.control) != old.control);
>
> - if (!WARN_ON_ONCE(vcpu->pre_pcpu == -1)) {
> - spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu));
> - list_del(&vcpu->blocked_vcpu_list);
> - spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu));
> - vcpu->pre_pcpu = -1;
> - }
> + spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu));
> + list_del(&vcpu->blocked_vcpu_list);
> + spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu));
> + vcpu->pre_pcpu = -1;
> }
>
> /*
> @@ -153,14 +151,12 @@ int pi_pre_block(struct kvm_vcpu *vcpu)
>
> WARN_ON(irqs_disabled());
> local_irq_disable();
> - if (!WARN_ON_ONCE(vcpu->pre_pcpu != -1)) {
> - vcpu->pre_pcpu = vcpu->cpu;
> - spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu));
> - list_add_tail(&vcpu->blocked_vcpu_list,
> - &per_cpu(blocked_vcpu_on_cpu,
> - vcpu->pre_pcpu));
> - spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu));
> - }
> +
> + vcpu->pre_pcpu = vcpu->cpu;
> + spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu));
> + list_add_tail(&vcpu->blocked_vcpu_list,
> + &per_cpu(blocked_vcpu_on_cpu, vcpu->pre_pcpu));
> + spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu));
>
> WARN(pi_desc->sn == 1,
> "Posted Interrupt Suppress Notification set before blocking");
Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
