From: Jesse Barnes <jbarnes@virtuousgeek.org>
To: linux-pci@atrey.karlin.mff.cuni.cz
Cc: benh@kernel.crashing.org,
Linux Kernel list <linux-kernel@vger.kernel.org>,
Matthew Wilcox <matthew@wil.cx>
Subject: Re: Weirdness in pci_read_bases()
Date: Mon, 3 Mar 2008 13:02:14 -0800 [thread overview]
Message-ID: <200803031302.14234.jbarnes@virtuousgeek.org> (raw)
In-Reply-To: <200803031257.33249.jbarnes@virtuousgeek.org>
On Monday, March 03, 2008 12:57 pm Jesse Barnes wrote:
> > Not only iommu's. On lots of platforms, we have the PCI MMIO space
> > mapped 1:N, that is, an access at MMIO location N turns into a PCI cycle
> > with address 0. So outbound PCI is effectively remapped, thus allowing
> > access to things like 0 etc... without punching holes in RAM and without
> > other dirty x86-like tricks.
>
> Right, bus address space is really a separate entity; I was just using
> IOMMUs as an example of that...
Err, wasn't really clear here. CPU->PCI space and PCI->host space are really
separate entities... IOMMUs will definitely affect the PCI->host mapping, and
CPU->PCI mappings can be arbitrarily complex as well, though as you say on
PCs it's typically just flatly mapped into CPU physical space somewhere.
Jesse
next prev parent reply other threads:[~2008-03-03 21:02 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-02-29 2:37 Weirdness in pci_read_bases() Benjamin Herrenschmidt
2008-02-29 7:15 ` Grant Grundler
2008-03-03 19:12 ` Jesse Barnes
2008-03-03 20:42 ` Benjamin Herrenschmidt
2008-03-03 20:57 ` Jesse Barnes
2008-03-03 21:02 ` Jesse Barnes [this message]
2008-03-03 21:29 ` Alan Cox
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