From mboxrd@z Thu Jan  1 00:00:00 1970
From: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
Subject: Re: [PATCH v2 5/8] iommu/io-pgtable-arm: Support lockless operation
Date: Tue, 27 Jun 2017 09:39:13 +0100
Message-ID: <20170627083912.GA5759@arm.com>
References: <cover.1498145008.git.robin.murphy@arm.com>
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To: Linu Cherian <linu.cherian-YGCgFSpz5w/QT0dZR+AlfA@public.gmane.org>
Cc: sunil.goutham-YGCgFSpz5w/QT0dZR+AlfA@public.gmane.org, wangzhou1-C8/M+/jPZTeaMJb+Lgu22Q@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, ray.jui-dY08KVG/lbpWk0Htik3J/w@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, thunder.leizhen-hv44wF8Li93QT0dZR+AlfA@public.gmane.org
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On Tue, Jun 27, 2017 at 10:41:55AM +0530, Linu Cherian wrote:
> On Fri Jun 23, 2017 at 05:04:05PM +0530, Linu Cherian wrote:
> > On Fri Jun 23, 2017 at 11:35:25AM +0100, Robin Murphy wrote:
> > > Note that on a coherent platform like ThunderX that's as good as just
> > > deleting it, because you'll never execute the case below. However, on
> > > reflection I think it can at least safely be downgraded to dma_wmb()
> > > (i.e. DMB) rather than a full DSB - would you be able to test what
> > > difference that makes?
> > 
> > The testing was done on Thunderx 1, which has a non coherent page table walk.
> > Yes, downgrading to dma_wmb() helps. With this change, performance is back to v1.
> > 
> 
> Should i send a patch for this ?

I already did it:

https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/commit/?h=for-joerg/arm-smmu/updates&id=77f3445866c39d8866b31d8d9fa47c7c20938e05

Will