From: Andi Kleen <andi@firstfloor.org>
To: Daniel Haid <d.haid@gogi.tv>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Andi Kleen <andi@firstfloor.org>,
linux-kernel@vger.kernel.org
Subject: Re: Question about iommu on x86_64 and radeon driver.
Date: Thu, 26 May 2011 01:05:44 +0200 [thread overview]
Message-ID: <20110525230544.GA4065@one.firstfloor.org> (raw)
In-Reply-To: <ae8450396be43e94c1ea724312428d4f@admin.gogi.tv>
On Wed, May 25, 2011 at 09:21:21PM +0100, Daniel Haid wrote:
> >Only if you allow 3GB or less in the machine. So you would have to do
> >mem=3G as well.
> >
> >The reason is that (and you can see that yourself by looking at the
> >E820), is that 1GB is actually _above_ the 4GB.
>
> Just another question on this one:
>
> Why can a driver not simply ask for DMA-capable memory, is this not
> what memory zones are for?
In many cases the memory gets passed into the driver.
If it's not already in the right boundaries it would need to copy through
a bounce buffer. That is what swiotlb does, if there's no IOMMU.
-Andi
next prev parent reply other threads:[~2011-05-25 23:05 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-22 21:56 Daniel Haid
2011-05-23 22:05 ` Konrad Rzeszutek Wilk
2011-05-23 23:45 ` Daniel Haid
2011-05-24 15:50 ` Konrad Rzeszutek Wilk
2011-05-24 21:33 ` Daniel Haid
2011-05-25 12:58 ` Konrad Rzeszutek Wilk
2011-05-25 14:28 ` Daniel Haid
2011-05-24 22:48 ` Andi Kleen
2011-05-25 10:00 ` Daniel Haid
2011-05-25 12:57 ` Konrad Rzeszutek Wilk
2011-05-25 14:51 ` Daniel Haid
2011-05-25 20:21 ` Daniel Haid
2011-05-25 23:05 ` Andi Kleen [this message]
2011-05-27 15:48 ` Daniel Haid
2011-05-27 15:55 ` Konrad Rzeszutek Wilk
2011-05-27 22:20 ` Daniel Haid
2011-05-31 13:45 ` Konrad Rzeszutek Wilk
2011-05-31 15:34 ` Daniel Haid
2011-05-31 16:02 ` Konrad Rzeszutek Wilk
[not found] ` <0a8cb4bcad7fcf091a6bbe158323bba0@admin.gogi.tv>
2011-05-31 16:20 ` Daniel Haid
[not found] ` <20110531190412.GA21245@dumpdata.com>
2011-05-31 19:57 ` Daniel Haid
2011-06-01 13:24 ` Konrad Rzeszutek Wilk
2011-06-01 16:10 ` Daniel Haid
2011-06-01 21:51 ` Andi Kleen
2011-06-01 21:58 ` Daniel Haid
2011-06-01 22:22 ` Andi Kleen
2011-06-03 17:31 ` [PATCH] tentative fix for radeon on systems >4GB without hardware iommu Daniel Haid
2011-06-03 20:44 ` Alex Deucher
2011-06-03 23:13 ` Konrad Rzeszutek Wilk
2011-06-06 17:45 ` Daniel Haid
2011-06-06 17:41 ` Daniel Haid
2011-06-06 19:08 ` Alex Deucher
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