From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: mm_pages_next() question
Date: Wed, 01 Apr 2009 11:40:30 +0300
Message-ID: <49D3287E.9070407@redhat.com>
References: <49CF6868.7040205@redhat.com> <20090331161831.GA4131@amt.cnet>
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To: Marcelo Tosatti <mtosatti@redhat.com>
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Marcelo Tosatti wrote:
> 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.
>   

I'm still missing something.   That if () tests for level == 
PT_PAGE_TABLE_LEVEL.  So it looks like we'll have batch sizes of 4, 1, 
1, 1, ... 3, 1, 1, 1, ...?


-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.