linux-kernel - Re: [PATCH v3 5/6] iommu/mediatek: Add mt8173 IOMMU driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20150727153148.GJ7557@n2100.arm.linux.org.uk>
Date:	Mon, 27 Jul 2015 16:31:48 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Robin Murphy <robin.murphy@....com>
Cc:	Yong Wu <yong.wu@...iatek.com>, Joerg Roedel <joro@...tes.org>,
	Thierry Reding <treding@...dia.com>,
	Mark Rutland <Mark.Rutland@....com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"pebolle@...cali.nl" <pebolle@...cali.nl>,
	"arnd@...db.de" <arnd@...db.de>,
	"srv_heupstream@...iatek.com" <srv_heupstream@...iatek.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Tomasz Figa <tfiga@...gle.com>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	Rob Herring <robh+dt@...nel.org>,
	Daniel Kurtz <djkurtz@...gle.com>,
	Sasha Hauer <kernel@...gutronix.de>,
	"cloud.chou@...iatek.com" <cloud.chou@...iatek.com>,
	"linux-mediatek@...ts.infradead.org" 
	<linux-mediatek@...ts.infradead.org>,
	"frederic.chen@...iatek.com" <frederic.chen@...iatek.com>,
	"mitchelh@...eaurora.org" <mitchelh@...eaurora.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Lucas Stach <l.stach@...gutronix.de>
Subject: Re: [PATCH v3 5/6] iommu/mediatek: Add mt8173 IOMMU driver

On Mon, Jul 27, 2015 at 02:23:26PM +0100, Robin Murphy wrote:
> On 16/07/15 10:04, Yong Wu wrote:
> >This patch adds support for mediatek m4u (MultiMedia Memory Management
> >Unit).
> >
> >Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> [...]
> >+static void mtk_iommu_flush_pgtable(void *ptr, size_t size, void *cookie)
> >+{
> >+       struct mtk_iommu_domain *domain = cookie;
> >+       unsigned long offset = (unsigned long)ptr & ~PAGE_MASK;
> >+
> >+       dma_map_page(domain->data->dev, virt_to_page(ptr), offset,
> >+                    size, DMA_TO_DEVICE);
> 
> Nit: this looks like it may as well be dma_map_single.
> 
> It would probably be worth following it with a matching unmap too, just to
> avoid any possible leakage bugs (especially if this M4U ever appears in a
> SoC supporting RAM above the 32-bit boundary).

Why not do the job properly?  Take a look at how I implemented the
streaming DMA API on Tegra SMMU (patch set recently sent out earlier
today).

There's no need for hacks like dma_map_page() (and discarding it's
return value) or dma_map_page() followed by dma_unmap_page().

-- 
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/