linux-kernel - Re: [PATCH] mm/mmu_notifier: restore set_pte_at

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Date:	Wed, 22 Jan 2014 14:10:46 +0100
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	Mike Rapoport <mike.rapoport@...ellosystems.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Izik Eidus <izik.eidus@...ellosystems.com>,
	Haggai Eran <haggaie@...lanox.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] mm/mmu_notifier: restore set_pte_at_notify semantics

On Wed, Jan 15, 2014 at 11:40:34AM +0200, Mike Rapoport wrote:
> Commit 6bdb913f0a70a4dfb7f066fb15e2d6f960701d00 (mm: wrap calls to
> set_pte_at_notify with invalidate_range_start and invalidate_range_end)
> breaks semantics of set_pte_at_notify. When calls to set_pte_at_notify
> are wrapped with mmu_notifier_invalidate_range_start and
> mmu_notifier_invalidate_range_end, KVM zaps pte during
> mmu_notifier_invalidate_range_start callback and set_pte_at_notify has
> no spte to update and therefore it's called for nothing.
> 
> As Andrea suggested (1), the problem is resolved by calling
> mmu_notifier_invalidate_page after PT lock has been released and only
> for mmu_notifiers that do not implement change_ptr callback.
> 
> (1) http://thread.gmane.org/gmane.linux.kernel.mm/111710/focus=111711
> 
> Reported-by: Izik Eidus <izik.eidus@...ellosystems.com>
> Signed-off-by: Mike Rapoport <mike.rapoport@...ellosystems.com>
> Cc: Andrea Arcangeli <aarcange@...hat.com>
> Cc: Haggai Eran <haggaie@...lanox.com>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> ---
>  include/linux/mmu_notifier.h | 31 ++++++++++++++++++++++++++-----
>  kernel/events/uprobes.c      | 12 ++++++------
>  mm/ksm.c                     | 15 +++++----------
>  mm/memory.c                  | 14 +++++---------
>  mm/mmu_notifier.c            | 24 ++++++++++++++++++++++--
>  5 files changed, 64 insertions(+), 32 deletions(-)

Reviewed-by: Andrea Arcangeli <aarcange@...hat.com>

Thanks!
Andrea
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