From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Olof Johansson <olof@lixom.net>
Cc: linuxppc-dev@ozlabs.org,
"cbe-oss-dev@ozlabs.org" <cbe-oss-dev@ozlabs.org>,
Arnd Bergmann <arnd@arndb.de>
Subject: Re: [Cbe-oss-dev] [PATCH 3/3] Cell IOMMU static mapping support
Date: Tue, 29 Jan 2008 08:16:17 +1100 [thread overview]
Message-ID: <1201554977.6815.189.camel@pasglop> (raw)
In-Reply-To: <20080128162343.GA19859@lixom.net>
On Mon, 2008-01-28 at 10:23 -0600, Olof Johansson wrote:
> Ok, makes sense.
>
> I was going to protest the hack for >32GB configs, with the motivation
> that just using the htab-backed window is way too small for such a
> config. However, with 32GB memory and 4K pages, that window is 512MB, so
> we should be fine.
Might be a problem with 64K pages tho... Or do we use the same
calculation ?
In addition, on those blades, really the only device that is limited to
32 bits (and thus is forced to use the iommu remapped region) is USB.
> Having that described in the patch (or at least in the patch description)
> to make it more clear could be good. That, and the fact that the mapping
> is offset on <32GB memory machines, and thus not really a 1:1 mapping.
Should be called a "linear" mapping.
> Does the cell I/O bridge reflect out accesses to 2-4GB on the bus
> again? If not, that could be another place to stick the dynamic range
> for large config machines.
On the PCI bus itself, 2-4GB is where MMIO sits.
Ben.
next prev parent reply other threads:[~2008-01-28 21:16 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-01-25 10:45 [PATCH 1/3] Add set_dma_ops() to match get_dma_ops() Michael Ellerman
2008-01-25 10:45 ` [PATCH 3/3] Cell IOMMU static mapping support Michael Ellerman
2008-01-25 13:12 ` [Cbe-oss-dev] " Geert Uytterhoeven
2008-01-26 2:51 ` Olof Johansson
2008-01-28 11:41 ` [Cbe-oss-dev] " Arnd Bergmann
2008-01-28 16:23 ` Olof Johansson
2008-01-28 21:16 ` Benjamin Herrenschmidt [this message]
2008-01-28 21:48 ` Olof Johansson
2008-01-28 21:37 ` Benjamin Herrenschmidt
2008-01-28 21:18 ` Benjamin Herrenschmidt
2008-01-25 10:45 ` [PATCH 2/3] Allocate the hash table under 1G on cell Michael Ellerman
2008-02-05 0:23 ` Benjamin Herrenschmidt
2008-02-05 0:23 ` [PATCH 1/3] Add set_dma_ops() to match get_dma_ops() Benjamin Herrenschmidt
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