lkml.org 
[lkml]   [2020]   [Oct]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 18/22] kvm: mmu: Support disabling dirty logging for the tdp MMU
On Wed, Oct 7, 2020 at 10:21 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 07/10/20 18:30, Ben Gardon wrote:
> >> I'm starting to wonder if another iterator like
> >> for_each_tdp_leaf_pte_root would be clearer, since this idiom repeats
> >> itself quite often. The tdp_iter_next_leaf function would be easily
> >> implemented as
> >>
> >> while (likely(iter->valid) &&
> >> (!is_shadow_present_pte(iter.old_spte) ||
> >> is_last_spte(iter.old_spte, iter.level))
> >> tdp_iter_next(iter);
> > Do you see a substantial efficiency difference between adding a
> > tdp_iter_next_leaf and building on for_each_tdp_pte_using_root with
> > something like:
> >
> > #define for_each_tdp_leaf_pte_using_root(_iter, _root, _start, _end) \
> > for_each_tdp_pte_using_root(_iter, _root, _start, _end) \
> > if (!is_shadow_present_pte(_iter.old_spte) || \
> > !is_last_spte(_iter.old_spte, _iter.level)) \
> > continue; \
> > else
> >
> > I agree that putting those checks in a wrapper makes the code more concise.
> >
>
> No, that would be just another way to write the same thing. That said,
> making the iteration API more complicated also has disadvantages because
> if get a Cartesian explosion of changes.

I wouldn't be too worried about that. The only things I ever found
worth making an iterator case for were:
Every SPTE
Every present SPTE
Every present leaf SPTE

And really there aren't many cases that use the middle one.

>
> Regarding the naming, I'm leaning towards
>
> tdp_root_for_each_pte
> tdp_vcpu_for_each_pte
>
> which is shorter than the version with "using" and still clarifies that
> "root" and "vcpu" are the thing that the iteration works on.

That sounds good to me. I agree it's similarly clear.

>
> Paolo
>

\
 
 \ /
  Last update: 2020-10-07 19:29    [W:0.109 / U:0.160 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site