linux-kernel - Re: [PATCH] mm: hugetlb: flush dcache before returning zeroed huge page to userspace

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Message-ID: <20120705141700.GI3399@mudshark.cambridge.arm.com>
Date:	Thu, 5 Jul 2012 15:17:00 +0100
From:	Will Deacon <will.deacon@....com>
To:	Hillf Danton <dhillf@...il.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"mhocko@...e.cz" <mhocko@...e.cz>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: hugetlb: flush dcache before returning zeroed huge
 page to userspace

On Thu, Jul 05, 2012 at 01:37:46PM +0100, Hillf Danton wrote:
> On Wed, Jul 4, 2012 at 10:32 PM, Will Deacon <will.deacon@....com> wrote:
> > When allocating and returning clear huge pages to userspace as a
> > response to a fault, we may zero and return a mapping to a previously
> > dirtied physical region (for example, it may have been written by
> > a private mapping which was freed as a result of an ftruncate on the
> > backing file). On architectures with Harvard caches, this can lead to
> > I/D inconsistency since the zeroed view may not be visible to the
> > instruction stream.
> >
> > This patch solves the problem by flushing the region after allocating
> > and clearing a new huge page. Note that PowerPC avoids this issue by
> > performing the flushing in their clear_user_page implementation to keep
> > the loader happy, however this is closely tied to the semantics of the
> > PG_arch_1 page flag which is architecture-specific.
> >
> > Acked-by: Catalin Marinas <catalin.marinas@....com>
> > Signed-off-by: Will Deacon <will.deacon@....com>
> > ---
> 
> Thanks:)
> 
> Acked-by: Hillf Danton <dhillf@...il.com>

Thanks Hillf. Which tree does this stuff usually go through?

Will
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