linux-kernel - Re: Patch "USB: Work around BIOS bugs by quiescing USB controllers earlier" causes MCEs

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Date:	Fri, 2 Oct 2009 21:28:32 +0200
From:	Mikael Pettersson <mikpe@...uu.se>
To:	Mikael Pettersson <mikpe@...uu.se>
Cc:	Nick Piggin <npiggin@...e.de>,
	David Woodhouse <dwmw2@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Patch "USB: Work around BIOS bugs by quiescing USB controllers earlier" causes MCEs

Mikael Pettersson writes:
 > Nick Piggin writes:
 >  > Hi,
 >  > 
 >  > Your patch db8be50c4307dac2b37305fc59c8dc0f978d09ea is causing my
 >  > ia64 Altix system to die with an MCE in early boot.
 > 
 > The same commit has been confirmed by two people on the ARM list
 > to cause boot failures on two different Intel XScale IOP machines.
 > The machines have serial consoles, but only show
 > 
 > Uncompressing Linux... done. Booting the kernel.
 > 
 > before they hang.

I've just investigated this on one of my ARM boxes that this commit kills.

The commit changed quirk_usb_early_handoff to be a FIXUP_HEADER, which
caused it to be invoked during the early stages of the platform's PCI
init (arch/arm/kernel/bios32.c). quirk_usb_handoff_uhci() gets a bogus
I/O base address, passes that down to uhci_reset_hc(), causing a kernel
page fault in the first "outw(UHCI_USBCMD_HCRESET, base + UHCI_USBCMD);",
causing the kernel to oops.

(All this occurs before the serial console works, so I had to add a
platform-specific puts() and lots of tracing statements.)

Changing this quirk back to a FIXUP_FINAL allows the platform's PCI
init to complete. Later on the generic pci_init() calls the quirk,
which now gets the correct I/O base address, and the outw()s in
uhci_reset_hc() don't fail.
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