On Wed, Sep 23, 2009 at 06:59:35AM -0700, David Woodhouse wrote: > On Wed, 2009-09-23 at 06:55 -0700, Greg Kroah-Hartman wrote: > > From: David Woodhouse <dwmw2@xxxxxxxxxxxxx> > > > > We are seeing a number of crashes in SMM, when VT-d is enabled while > > 'Legacy USB support' is enabled in various BIOSes. > > > > The BIOS is supposed to indicate which addresses it uses for DMA in a > > special ACPI table ("RMRR"), so that we can punch a hole for it when we > > set up the IOMMU. > > > > The problem is, as usual, that BIOS engineers are totally incompetent. > > They write code which will crash if the DMA goes AWOL, and then they > > either neglect to provide an RMRR table at all, or they put the wrong > > addresses in it. And of course they don't do _any_ QA, since that would > > take too much time away from their crack-smoking habit. > > > > The real fix, of course, is for consumers to refuse to buy motherboards > > which only have closed-source firmware available. If we had _open_ > > firmware, bugs like this would be easy to fix. > > > > Since that's something I can only dream about, this patch implements an > > alternative -- ensuring that the USB controllers are handed off from the > > BIOS and quiesced _before_ the IOMMU is initialised. That would have > > been a much better design than this RMRR nonsense in the first place, of > > course. The bootloader has no business doing DMA after the OS has booted > > anyway. > > > > Signed-off-by: David Woodhouse <David.Woodhouse@xxxxxxxxx> > > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx> > > --- > > That was in the iommu tree when I asked Linus to pull it yesterday. Heh, then git will resolve the merge just fine, right? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html