KVM: VMX: Drop unnecessary PI logic to handle impossible conditions

Drop sanity checks on the validity of the previous pCPU when handling
vCPU block/unlock for posted interrupts.  The intention behind the sanity
checks is to avoid memory corruption in case of a race or incorrect locking,
but the code has been stable for a few years now and the checks get in
the way of eliminating kvm_vcpu.pre_cpu.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211009021236.4122790-23-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
index ee4ddc6..f15d4a7 100644 (file)
--- a/arch/x86/kvm/vmx/posted_intr.c
+++ b/arch/x86/kvm/vmx/posted_intr.c
@@ -123,12 +123,10 @@ 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;
 }
 
 /*
@@ -156,14 +154,12 @@ 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));
 
        do {
                old.control = new.control = pi_desc->control;