From: Benjamin LaHaise <bcrl@kvack.org>
To: Simon Baatz <gmbnomis@gmail.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>,
Helge Deller <deller@gmx.de>,
linux-aio@kvack.org, linux-kernel@vger.kernel.org,
linux-parisc@vger.kernel.org
Subject: Re: [PATCH] aio: fix D-cache aliasing issues
Date: Sat, 16 Nov 2013 15:09:59 -0500 [thread overview]
Message-ID: <20131116200959.GA14098@kvack.org> (raw)
In-Reply-To: <20131116200717.GA18939@schnuecks.de>
On Sat, Nov 16, 2013 at 09:07:18PM +0100, Simon Baatz wrote:
> On Fri, Nov 15, 2013 at 02:42:05PM -0800, James Bottomley wrote:
> > On Fri, 2013-11-15 at 23:05 +0100, Helge Deller wrote:
> > > When a user page mapping is released via kunmap*() functions, the D-cache needs
> > > to be flushed via flush_dcache_page() to avoid D-cache aliasing issues.
> > >
> > > This patch fixes aio on the parisc platform (and probably others).
> >
> > This should be flush_kernel_dcache_page(). flush_dcache_page() is for
> > full coherency but for unmap, we know the page was coherent going in and
> > may have been modified by the kernel, so only the kernel view needs to
> > be sync'd. Technically, by the kernel API, the flush should be done
> > *before* unmapping. This would have mattered on parisc until we did
> > flush via tmpalias which means we no-longer care if the mapping for the
> > flush exists or not because we always recreate it via the tmpalias
> > pages.
>
> On ARM, flush_kernel_dcache_page() actually assumes that the page is
> mapped. It avoids double flushing of highmem pages by not flushing
> in those cases where kunmap_atomic() already takes care of flushing.
Helge -- are you going to resubmit a version of this patch that makes the
recommended change?
-ben
>
>
> - Simon
--
"Thought is the essence of where you are now."
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WARNING: multiple messages have this Message-ID (diff)
From: Benjamin LaHaise <bcrl@kvack.org>
To: Simon Baatz <gmbnomis@gmail.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>,
Helge Deller <deller@gmx.de>,
linux-aio@kvack.org, linux-kernel@vger.kernel.org,
linux-parisc@vger.kernel.org
Subject: Re: [PATCH] aio: fix D-cache aliasing issues
Date: Sat, 16 Nov 2013 15:09:59 -0500 [thread overview]
Message-ID: <20131116200959.GA14098@kvack.org> (raw)
In-Reply-To: <20131116200717.GA18939@schnuecks.de>
On Sat, Nov 16, 2013 at 09:07:18PM +0100, Simon Baatz wrote:
> On Fri, Nov 15, 2013 at 02:42:05PM -0800, James Bottomley wrote:
> > On Fri, 2013-11-15 at 23:05 +0100, Helge Deller wrote:
> > > When a user page mapping is released via kunmap*() functions, the D-cache needs
> > > to be flushed via flush_dcache_page() to avoid D-cache aliasing issues.
> > >
> > > This patch fixes aio on the parisc platform (and probably others).
> >
> > This should be flush_kernel_dcache_page(). flush_dcache_page() is for
> > full coherency but for unmap, we know the page was coherent going in and
> > may have been modified by the kernel, so only the kernel view needs to
> > be sync'd. Technically, by the kernel API, the flush should be done
> > *before* unmapping. This would have mattered on parisc until we did
> > flush via tmpalias which means we no-longer care if the mapping for the
> > flush exists or not because we always recreate it via the tmpalias
> > pages.
>
> On ARM, flush_kernel_dcache_page() actually assumes that the page is
> mapped. It avoids double flushing of highmem pages by not flushing
> in those cases where kunmap_atomic() already takes care of flushing.
Helge -- are you going to resubmit a version of this patch that makes the
recommended change?
-ben
>
>
> - Simon
--
"Thought is the essence of where you are now."
next prev parent reply other threads:[~2013-11-16 20:09 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-15 22:05 [PATCH] aio: fix D-cache aliasing issues Helge Deller
2013-11-15 22:42 ` James Bottomley
2013-11-16 20:07 ` Simon Baatz
2013-11-16 20:09 ` Benjamin LaHaise [this message]
2013-11-16 20:09 ` Benjamin LaHaise
2013-11-17 21:23 ` Helge Deller
2013-11-17 21:49 ` James Bottomley
2013-11-17 23:47 ` Helge Deller
2013-11-17 23:47 ` Helge Deller
2013-11-18 0:52 ` James Bottomley
2013-11-18 1:15 ` John David Anglin
2013-11-18 1:50 ` James Bottomley
2013-11-18 1:03 ` John David Anglin
2013-11-18 10:54 ` Simon Baatz
2013-11-18 11:24 ` Aw: " Helge Deller
2013-11-16 22:06 ` James Bottomley
2013-11-16 22:06 ` James Bottomley
2013-11-16 22:32 ` John David Anglin
2013-11-16 22:37 ` James Bottomley
2013-11-16 22:49 ` John David Anglin
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