Re: mm_pages_next() question

[Marcelo Tosatti <mtosatti@redhat.com>]

On Sun, Mar 29, 2009 at 03:24:08PM +0300, Avi Kivity wrote:
>> static int mmu_pages_next(struct kvm_mmu_pages *pvec,
>>                           struct mmu_page_path *parents,
>>                           int i)
>> {
>>         int n;
>>
>>         for (n = i+1; n < pvec->nr; n++) {
>>                 struct kvm_mmu_page *sp = pvec->page[n].sp;
>>
>>                 if (sp->role.level == PT_PAGE_TABLE_LEVEL) {
>>                         parents->idx[0] = pvec->page[n].idx;
>>                         return n;
>>                 }
>>
>>                 parents->parent[sp->role.level-2] = sp;
>>                 parents->idx[sp->role.level-1] = pvec->page[n].idx;
>>         }
>>
>>         return n;
>> }
>
> Do we need to break out of the loop if we switch parents during the loop  
> (since that will give us a different mmu_page_path)?  Or are callers  
> careful to only pass pvecs which belong to the same shadow page?

This function builds mmu_page_path for a number of pagetable (leaf)
pages. Whenever the path changes, mmu_page_path will be rebuilt.

The pages in the pvec must be organized as follows:

level4, level3, level2, level1, level1, level1, ...., level3, level2,
level1, level1, ...

So you don't have to repeat higher levels for a number of leaf pages.