linux-kernel - Re: [RFC 09/10] drm/tegra: Add IOMMU support

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Date:	Wed, 5 Nov 2014 10:50:05 +0100
From:	Thierry Reding <thierry.reding@...il.com>
To:	Sean Paul <seanpaul@...gle.com>
Cc:	Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Stephen Warren <swarren@...dotorg.org>,
	Arnd Bergmann <arnd@...db.de>,
	Will Deacon <will.deacon@....com>,
	Joerg Roedel <joro@...tes.org>,
	Cho KyongHo <pullip.cho@...sung.com>,
	Grant Grundler <grundler@...omium.org>,
	Dave Martin <Dave.Martin@....com>,
	Marc Zyngier <marc.zyngier@....com>,
	Hiroshi Doyu <hdoyu@...dia.com>,
	Olav Haugan <ohaugan@...eaurora.org>,
	Paul Walmsley <pwalmsley@...dia.com>,
	Rhyland Klein <rklein@...dia.com>,
	Allen Martin <amartin@...dia.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Linux IOMMU <iommu@...ts.linux-foundation.org>,
	Linux ARM Kernel <linux-arm-kernel@...ts.infradead.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Stéphane Marchesin <marcheu@...gle.com>
Subject: Re: [RFC 09/10] drm/tegra: Add IOMMU support

On Wed, Oct 01, 2014 at 11:54:11AM -0400, Sean Paul wrote:
> On Tue, Sep 30, 2014 at 2:48 PM, Sean Paul <seanpaul@...gle.com> wrote:
> > On Thu, Jun 26, 2014 at 4:49 PM, Thierry Reding <thierry.reding@...il.com> wrote:
> >> diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c
[...]
> >>  static void tegra_bo_destroy(struct drm_device *drm, struct tegra_bo *bo)
> >>  {
> >> -       dma_free_writecombine(drm->dev, bo->gem.size, bo->vaddr, bo->paddr);
> >> +       if (!bo->pages)
> >> +               dma_free_writecombine(drm->dev, bo->gem.size, bo->vaddr,
> >> +                                     bo->paddr);
> 
> One more thing. If tegra_bo_alloc fails, we'll have bo->vaddr == NULL
> and bo->paddr == ~0 here, which causes a crash.
> 
> I posted https://lkml.org/lkml/2014/9/30/659 to check for the error
> condition in the mm code, but it seems like reviewer consensus is to
> check for this before calling free.
> 
> As such, we'll need to make sure bo->vaddr != NULL before calling
> dma_free_writecombine to avoid this situation.
> 
> Would you prefer I send a patch up to fix this separately, or would
> you like to roll this into your next version?

I've rolled this check into my series because I touch that area of code
anyway.

Thanks for bringing it up.

Thierry

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