On Fri, Aug 02, 2024, Steve Rutherford wrote:
> On Fri, Aug 2, 2024 at 1:01 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
> > @@ -4178,9 +4181,9 @@ static int vcpu_get_pid(void *data, u64 *val)
> > {
> > struct kvm_vcpu *vcpu = data;
> >
> > - rcu_read_lock();
> > - *val = pid_nr(rcu_dereference(vcpu->pid));
> > - rcu_read_unlock();
> > + read_lock(&vcpu->pid_lock);
> > + *val = pid_nr(vcpu->pid);
> > + read_unlock(&vcpu->pid_lock);
> > return 0;
> > }
> >
> > @@ -4466,7 +4469,7 @@ static long kvm_vcpu_ioctl(struct file *filp,
> > r = -EINVAL;
> > if (arg)
> > goto out;
> > - oldpid = rcu_access_pointer(vcpu->pid);
> > + oldpid = vcpu->pid;
>
> Overall this patch looks correct, but this spot took me a moment, and
> I want to confirm. This skips the reader lock since writing only
> happens just below, under the vcpu lock, and we've already taken that
> lock?
Yep, exactly.
