Re: huh startup_ipi_hook?

[Jeremy Fitzhardinge <jeremy@goop.org>]

Eric W. Biederman wrote:
> So conceptually I think the concept makes sense but implementation
> wise I think what is currently present is totally ridiculous.

I tend to agree. For Xen I added smp_ops as an adjunct to paravirt_ops,
which is basically the interface defined in linux/smp.h:

struct smp_ops
{
	void (*smp_prepare_boot_cpu)(void);
	void (*smp_prepare_cpus)(unsigned max_cpus);
	int (*cpu_up)(unsigned cpu);
	void (*smp_cpus_done)(unsigned max_cpus);

	void (*smp_send_stop)(void);
	void (*smp_send_reschedule)(int cpu);
	int (*smp_call_function_mask)(cpumask_t mask,
				      void (*func)(void *info), void *info,
				      int wait);
};


This is a fairly close match to Xen's requirements. Certainly, anything
APIC-related is useless for us, since there's no APIC emulation going on.

I won't speak for Zach, but his counter-argument is generally along the
lines of "we can just make use of the existing code with a couple of
little hooks near the bottom". But I wonder if the existing genapic
interface can be used (or extended) to cover these cases without having
needing to have APIC-level interfaces in paravirt_ops.

Are you reviewing -mm? That's basically OK, but there's newer stuff in
Andi's patch queue.

J