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

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Date:	Mon, 18 Jun 2012 22:20:10 +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

On Mon, 18 Jun 2012 15:11:42 +0300
Avi Kivity <avi@...hat.com> wrote:


> >  	kvm_for_each_memslot(memslot, slots) {
> > -		gfn_t gfn = hva_to_gfn(hva, memslot);
> > +		gfn_t gfn = hva_to_gfn(start_hva, memslot);
> > +		gfn_t end_gfn = hva_to_gfn(end_hva, memslot);
> 
> These will return random results which you then use in min/max later, no?

Yes, I will follow your advice: check-then-convert (or check-and-convert).

> > @@ -1212,7 +1218,9 @@ static int kvm_handle_hva(struct kvm *kvm, unsigned long hva,
> >  				rmapp = __gfn_to_rmap(gfn, j, memslot);
> >  				ret |= handler(kvm, rmapp, data);
> 
> Potential for improvement: don't do 512 iterations on same large page.
> 
> Something like
> 
>     if ((gfn ^ prev_gfn) & mask(level))
>         ret |= handler(...)
> 
> with clever selection of the first prev_gfn so it always matches (~gfn
> maybe).

Really nice.
I'm sure that will make this much faster!

Thanks,
	Takuya
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