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Re: [Xen-devel] Fwd: Re: struct page field arrangement

To: Jan Beulich <jbeulich@xxxxxxxxxx>, Keir Fraser <keir@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Fwd: Re: struct page field arrangement
From: Keir Fraser <keir@xxxxxxxxxxxxx>
Date: Thu, 01 Mar 2007 12:12:13 +0000
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On 1/3/07 11:45, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

>> Can we confident that the mm_pin/mm_unpin code (which walks pagetables and
>> has to find every page to make every one read-only or writable) is safe?
>> Presumably for this to be true we need to be sure that noone can meanwhile
>> concurrently be populating the pagetable we are walking with extra
>> pgds/puds/pmds/ptes...
> Since the pin/unpin walking only cares about pgd/pud/pmd entries,
> synchronization
> is guaranteed through mm->page_table_lock. The pte lock is used only for leaf
> entries, which are of no concern to (un)pinning.

Oh yes, of course.

By the way, I think your proposed patch looks okay. However we already use
page->index for foreign pages, in netback. Perhaps page->lru is also fair
game? :-)


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