linux-kernel - Re: [PATCH 01/10] ksm: add mmu_notifier set_pte_at

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Date:	Mon, 20 Jul 2009 10:48:52 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Izik Eidus <ieidus@...hat.com>
CC:	akpm@...ux-foundation.org, hugh.dickins@...cali.co.uk,
	aarcange@...hat.com, chrisw@...hat.com, avi@...hat.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	nickpiggin@...oo.com.au
Subject: Re: [PATCH 01/10] ksm: add mmu_notifier set_pte_at_notify()

Izik Eidus wrote:
> From: Izik Eidus <ieidus@...hat.com>
> 
> The set_pte_at_notify() macro allows setting a pte in the shadow page
> table directly, instead of flushing the shadow page table entry and then
> getting vmexit to set it.  It uses a new change_pte() callback to do so.
> 
> set_pte_at_notify() is an optimization for kvm, and other users of
> mmu_notifiers, for COW pages.  It is useful for kvm when ksm is used,
> because it allows kvm not to have to receive vmexit and only then map
> the ksm page into the shadow page table, but instead map it directly
> at the same time as Linux maps the page into the host page table.
> 
> Users of mmu_notifiers who don't implement new mmu_notifier_change_pte()
> callback will just receive the mmu_notifier_invalidate_page() callback.
> 
> Signed-off-by: Izik Eidus <ieidus@...hat.com>
> Signed-off-by: Chris Wright <chrisw@...hat.com>
> Signed-off-by: Hugh Dickins <hugh.dickins@...cali.co.uk>

Acked-by: Rik van Riel <riel@...hat.com>

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