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Date: Sat, 6 Sep 2008 17:49:35 +0200 From: Ingo Molnar <mingo@...e.hu> To: David Woodhouse <dwmw2@...radead.org> Cc: linux-kernel@...r.kernel.org, andi@...stfloor.org, arjan@...radead.org, torvalds@...ux-foundation.org, sfr@...b.auug.org.au, Jesse Barnes <jbarnes@...tuousgeek.org> Subject: Re: [PATCH] Blacklist DMAR on Intel G31/G33 chipsets * David Woodhouse <dwmw2@...radead.org> wrote: > On Fri, 2008-09-05 at 20:34 +0200, Ingo Molnar wrote: > > * David Woodhouse <dwmw2@...radead.org> wrote: > > > > > Some BIOSes (the Intel DG33BU, for example) wrongly claim to have DMAR > > > when they don't. Avoid the resulting crashes when it doesn't work as > > > expected. > > > > > > Signed-off-by: David Woodhouse <David.Woodhouse@...el.com> > > > --- > > > > > > This time, I build-tested it with CONFIG_DMAR actually enabled. Sorry. > > > I'd still be grateful if someone could test it on a DG33BU with the > > > old BIOS though, since I've killed mine. I tested the DMI version, but > > > not this one. > > > > ok - fixing this makes sense. I have two worries about this patch. > > > > Firstly, the quirk is keyed off an ACPI capability which is quite bad if > > someone boots with ACPI off. (which is still quite possible) The DMAR is > > PCI enumerated so there's nothing inherently ACPI about this. A DMI > > quirk (which will work even if ACPI is disabled) looks more robust. > > No, the intel-iommu code is isn't PCI-enumerated -- it all depends on > that ACPI table, unfortunately. [...] ah, you are right ... and i thought i could trust grep -i acpi drivers/pci/intel-iommu.c coming up empty ;-) Jesse's call obviously, but the DMI thing local to intel-iommu.c still looks better to me in all regards. I'm no fan of DMI in general - it just doesnt scale - but here a crappy BIOS gets punished with a DMI quirk and that's OK. Ingo -- 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/
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