linux-kernel - Re: [RFC PATCH 0/3] iommu: Add range flush operation

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Message-ID: <20150929122232.GH3036@8bytes.org>
Date:	Tue, 29 Sep 2015 14:22:32 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	Tomasz Figa <tfiga@...omium.org>, iommu@...ts.linux-foundation.org,
	Hiroshi Doyu <hdoyu@...dia.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Vince Hsu <vince.h@...dia.com>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Paul Walmsley <paul@...an.com>,
	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	Mikko Perttunen <mperttunen@...dia.com>,
	Will Deacon <will.deacon@....com>,
	Alex Williamson <alex.williamson@...hat.com>,
	Arnd Bergmann <arnd@...db.de>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Antonios Motakis <a.motakis@...tualopensystems.com>,
	Olav Haugan <ohaugan@...eaurora.org>,
	Nicolas Iooss <nicolas.iooss_linux@....org>,
	linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: Re: [RFC PATCH 0/3] iommu: Add range flush operation

On Tue, Sep 29, 2015 at 11:27:14AM +0200, Thierry Reding wrote:
> On Tue, Sep 29, 2015 at 02:25:23PM +0900, Tomasz Figa wrote:
> >  3) possibility of exporting the iommu_flush() operation and providing
> >     unsynchronized map/unmap operations for subsystems with even higher
> >     requirements for performance (e.g. drivers/gpu/drm).
> 
> That would require passing in some sort of flag that the core shouldn't
> be flushing itself, right? Currently it would flush on every map/unmap.

Not necessarily. Introducing a flag would require updating all callers,
so while at it we could also just change the semantics of map/unmap to
require an explicit flush afterwards (only if it turns out that such an
iommu_flush() function is really needed).



	Joerg

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