Messages in this thread | | | Date | Tue, 24 Feb 2004 08:27:20 -0800 | From | Mike Fedyk <> | Subject | Re: IOMMUs was Re: Intel vs AMD x86-64 |
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On Tue, Feb 24, 2004 at 09:50:02AM -0600, richard.brunner@amd.com wrote: > > > -----Original Message----- > > From: Andi Kleen [mailto:ak@suse.de] > > > > On Opteron the IOMMU code (ab)uses the built in AGPv3 GART in > > the CPU, which > > was originally intended for AGP. AMD converted it to be able > > to remap PCI especially for Linux, which I think deserves applause. > > > > It works surprisingly well even though it was not designed as > > a real IOMMU. Of course one of the main advantages of a real > > IOMMU - preventing arbitary memory corruption from broken > > devices - is lost because the remapping table is just a hole > > in the memory. I'm > > secretly hoping that when there is more support for Linux at > > chipset vendors they will someday add a bit to isolate all > > traffic that doesn't go through the GART from the main > > memory. This way you could get a much more reliable system > > that can tolerate broken PCI devices at a moderate > > performance penalty. > > Andi is being modest. It was he and Andrea Arcangeli who convinced > me we had a problem. We found a way to trick the AGP > GART hardware into helping, and then they turned it into a > "real" solution and helped us work the warts out of the BIOS > to enable it.
Yowza! Open source helping to make better processors. :-D - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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