Re: [GIT PULL] Xen APIC hooks (with io_apic_ops)

Ingo Molnar
2009-05-19T12:36:05Z

* Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> Hi Ingo,
>
> Here's a revised set of the Xen APIC changes which adds
> io_apic_ops to allow Xen to intercept IO APIC access operations.

In a previous discussion you said:

> IO APIC operations are not even slightly performance critical? Are
> they ever used on the interrupt delivery path?

Since they are not performance critical, then why doesnt Xen catch
the IO-APIC accesses, and virtualizes the device?

If you want to hook into the IO-APIC code at such a low level, why
dont you hook into the _hardware_ API - i.e. catch those
setup/routing modifications to the IO-APIC space. No Linux changes
are needed in that case.

Ingo