linux-kernel - Re: [PATCH 3/4] KVM: MMU: Make kvm_handle

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Date:	Thu, 21 Jun 2012 22:41:59 +0900
From:	Takuya Yoshikawa <takuya.yoshikawa@...il.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>,
	mtosatti@...hat.com, agraf@...e.de, paulus@...ba.org,
	aarcange@...hat.com, kvm@...r.kernel.org, kvm-ppc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] KVM: MMU: Make kvm_handle_hva() handle range of
 addresses

I should have read this before sending v2...

On Thu, 21 Jun 2012 11:24:59 +0300
Avi Kivity <avi@...hat.com> wrote:

> > 1. Separate rmap_pde from lpage_info->write_count and
> >    make this a simple array. (I once tried this.)
> > 
> 
> This has the potential to increase cache misses, but I don't think it's
> a killer.  The separation can simplify other things as well.

Yes, I think so too.

IIRC, write_count and rmap_pde are not used together so often.

> > 2. Use gfn_to_index() and loop over rmap array:

...

> >   /* main part */
> >   for each level {
> >       rmapp = __gfn_to_rmap(gfn_start, level, memslot);
> >       for (idx = gfn_to_index(gfn_start, memslot->base_gfn, level);
> >            idx < gfn_to_index(gfn_end, memslot->base_gfn, level); idx++) {
> >               ...
> >           /* loop over rmap array */
> >           ret |= handler(kvm, rmapp + idx, data);
> >       }
> >   }
> > 
> 
> Probably want idx <= gfn_to_index(gfn_end-1, ...) otherwise we fail on
> small slots.

I was thinking the same thing when making v2.
But I will check the boundary condition again.

(mmu_notifier + memslot + lpage + rmap...) * alignment...
Very confusing.

Thanks,
	Takuya
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