PARAVIRT_GUEST bug? [was: Stable regression: usb-storage is stuckin 2.6.26.5]
From: Michael Tokarev
Date: Tue Sep 16 2008 - 04:12:08 EST
Michael Tokarev wrote:
[usb-storage hangs on asus M2NPV-VM (nVidia GeForce 6150/nForce 430)
motherboard with latest bios]
Ok, it turned out to be pretty.. interesting.
It's not a regression within -stable kernel series. The problem
happens when BOTH are true:
- using latest BIOS for this mobo (1401), AND
- enabling KVM_GUEST in kernel.
The only difference in my kernel config between .1 and .5 was
to enable KVM_GUEST and KVM_CLOCK, and also I2C_HELPER_AUTO
which was added by kernel update.
Going with previous BIOS (1201) OR disabling PARAVIRT_GUEST
fixes the problem. I'll try to figure out which config
option is at problem here.
After seeing similar situation on another motherboard, I
become curious.
Here's the result: M3A78-EM motherboard (also from Asus),
AMD780G/SB700 etc. Updating to one of the latest bios
makes the system unbootable. Kernel hangs on boot right
after displaying
SLUB: Genslabs=12, HWalign=64, Order=0-1, MinObjects=4, CPUs=2, Nodes=1
Reverting to the older BIOS or disabling PARAVIRT_GUEST in kernel
fixes this (turning off KVM_GUEST isn't enough), and kernel happily
boots further, with next line being
hpet clockevent registered
...
Reportedly, another Asus motherboard (M2N-SLI DELUXE) also hangs
with new BIOS and KVM_GUEST optimizations turned on, but not on
older BIOS.
So it's quite.. funny. At least SOME latest BIOSes from Asustec,
together with PARAVIRT_GUEST, -- a problem. Don't do either of
those, and it's all ok.
The question is if Asus introduced the same bug in quite.. some
of their recent BIOSes, or PARAVIRT_GUEST code is somehow buggy
and the bug is exposed by new BIOS code.
Any hints on this? ;)
Thanks!
/mjt
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