Re: [PATCH v2 4/5] KVM: Kick resamplefd for split kernel irqchip

[Peter Xu]

On Thu, Mar 05, 2020 at 04:58:57PM -0700, Alex Williamson wrote:

Hi, Alex,

[...]

> > +bool kvm_resample_fd_notify(int gsi)
> > +{
> > +    KVMResampleFd *rfd;
> > +
> > +    if (!kvm_irqchip_is_split()) {
> > +        return false;
> > +    }
> 
> Nit, checking split irqchip here seems unnecessary.  We're only adding
> and removing list entries based on split irqchip below, so the list
> would be empty anyway, unless another user comes along that might have
> a reason for this functionality that isn't as tied to split irqchip.

Right, now it's more or less a hint to readers, and we can remove it.
I'll see whether I'll repost a new version, and I'll drop it if so.

> 
> Overall the series looks like a big improvement versus falling back to
> our crappy generic EOI hackery with split irqchip.  Thanks,

Yes I was pretty happy to see the numbers too when I first tested the
series, after all I was still uncertain about how much overhead the
userspace EOI would take on the irq return path.  It turns out that
the injection seems to be more important.

In all cases, major credits go to Paolo for the idea. :)

Thanks,

-- 
Peter Xu