On Thu, Aug 12, 2021, Paolo Bonzini wrote:
> On 12/08/21 19:07, Sean Christopherson wrote:
> > Yeah, I was/am on the fence too, I almost included a blurb in the cover letter
> > saying as much. I'll do that for v2 and let Paolo decide.
>
> I think it makes sense to have it. You can even use the ternary operator
Hah, yeah, I almost used a ternary op. Honestly don't know why I didn't, guess
my brain flipped a coin.
>
> /*
> * When zapping everything, all entries at the top level
> * ultimately go away, and the levels below go down with them.
> * So do not bother iterating all the way down to the leaves.
The subtle part is that try_step_down() won't actually iterate down because it
explicitly rereads and rechecks the SPTE.
if (iter->level == iter->min_level)
return false;
/*
* Reread the SPTE before stepping down to avoid traversing into page
* tables that are no longer linked from this entry.
*/
iter->old_spte = READ_ONCE(*rcu_dereference(iter->sptep)); \
---> this is the code that is avoided
child_pt = spte_to_child_pt(iter->old_spte, iter->level); /
if (!child_pt)
return false;
My comment wasn't all that accurate either. Maybe this?
/*
* No need to try to step down in the iterator when zapping all SPTEs,
* zapping the top-level non-leaf SPTEs will recurse on their children.
*/
int min_level = zap_all ? root->role.level : PG_LEVEL_4K;
> */
> int min_level = zap_all ? root->role.level : PG_LEVEL_4K;
>
> Paolo
>
