Re: [PATCH RFC] paravirt_ops: refactor struct paravirt_opsinto smaller pv_*_ops

From: Zachary Amsden
Date: Fri Sep 28 2007 - 15:02:39 EST

On Fri, 2007-09-28 at 11:49 -0700, Jeremy Fitzhardinge wrote:
> > We shouldn't need to export pv_init_ops.
> No. The only ones I export are:
> EXPORT_SYMBOL_GPL(pv_time_ops);
> EXPORT_SYMBOL_GPL(pv_cpu_ops);
> EXPORT_SYMBOL_GPL(pv_mmu_ops);
> EXPORT_SYMBOL_GPL(pv_apic_ops);
> EXPORT_SYMBOL (pv_irq_ops);

Nicely done. I know of some out of tree modules which use part of the
pv_cpu_ops and pv_mmu_ops, but we should not worry about such things,
and it turns out those modules don't need to be virtualized anyway.

> > It is debatable whether
> > CR2/CR3 should be part of CPU or MMU ops.
> Yeah, I was in two minds. CR3, at least, should be grouped with the
> other tlb operations, wherever they go. And while they're privileged
> CPU instructions (cpu_ops), they're more logically related to the rest
> of the mmu state. On the other hand, we could have an ops structure
> specifically dedicated to pagetable manipulations, and put the cr3/tlb
> ops elsewhere.

I'm not against either approach. I think the way you did it is fine.
If it were up to me, I would probably have driven myself crazy splitting
hairs on it until I was bald.

> > Also, can we drop write_cr2?
> > It isn't used anywhere, so the only reason to keep it is symmetry.
> > Which was a fine argument when it was an inline, but now it just adds
> > unused junk to the code.
> >
> I think its used in some cpu state save/restore code, but its not
> relevant to pv-ops.

Ah yes, it is used there. We actually exercise some of those paths, but
they don't need to be strictly virtualized.


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