linux-kernel - Re: [PATCH 28/83] mm: Change timing of notification to IOMMUs about a page to be invalidated

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Message-Id: <20140710151551.55646da50617fe9997e2830c@linux-foundation.org>
Date:	Thu, 10 Jul 2014 15:15:51 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Oded Gabbay <oded.gabbay@...il.com>
Cc:	David Airlie <airlied@...ux.ie>,
	Alex Deucher <alexander.deucher@....com>,
	Jerome Glisse <j.glisse@...il.com>,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	John Bridgman <John.Bridgman@....com>,
	Andrew Lewycky <Andrew.Lewycky@....com>,
	Joerg Roedel <joro@...tes.org>, linux-mm <linux-mm@...ck.org>,
	Oded Gabbay <oded.gabbay@....com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Hugh Dickins <hughd@...gle.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Jérôme Glisse <jglisse@...hat.com>,
	Jianyu Zhan <nasa4836@...il.com>
Subject: Re: [PATCH 28/83] mm: Change timing of notification to IOMMUs about
 a page to be invalidated

On Fri, 11 Jul 2014 00:53:26 +0300 Oded Gabbay <oded.gabbay@...il.com> wrote:

> From: Andrew Lewycky <Andrew.Lewycky@....com>
> 
> This patch changes the location of the mmu_notifier_invalidate_page function
> call inside try_to_unmap_one. The mmu_notifier_invalidate_page function
> call tells the IOMMU that a pgae should be invalidated.
> 
> The location is changed from after releasing the physical page to
> before releasing the physical page.
> 
> This change should prevent the bug that would occur in the
> (rare) case where the GPU attempts to access a page while the CPU
> attempts to swap out that page (or discard it if it is not dirty).

um OK, but what is the effect on all the other
mmu_notifier_ops.invalidate_page() implementations?

Please spell this out in full detail within the changelog and be sure
to cc the affected maintainers.


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