Re: [PATCH] hw/intc/ioapic: Update KVM routes before redelivering IRQ, on RTE update

[David Woodhouse]

On Thu, 2023-03-09 at 11:55 -0500, Peter Xu wrote:
> 
> There're four devices that can hook onto this, IIUC.  Besides IOAPIC and
> VFIO, there's also ivshmem and vhost.  IIUC we'll need to change all the
> four devices to implement this.

If you grep for kvm_irqchip_add_irqfd_notifier() there are more than that.

There's a bunch of largely duplicated code, with different code paths
for kvm_irqfds_enabled() and other variants. In code that I don't think
should even have to *know* about KVM, should it? 

I think I'd like to provide a generic set of helpers which just allow
callers to register a virtual IRQ and then trigger it manually and/or
attach an irqfd (and a resamplefd, qv) to it.

This new helper code can then cope with listening in userspace on that
fd if/when it needs to, and can even work for the non-KVM case. The
actual devices get a *lot* simpler.

It'll *broadly* look like the existing kvm_irqchip_* functions but be a
lot simpler to use.

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