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SubjectRe: linux-next: Tree for June 13: IO APIC breakage on HP nx6325
On Sun, 29 Jun 2008, Ingo Molnar wrote:

> > You may argue this is a regression, but this is simply the cost paid
> > for progress -- the kernel stays within the spec as defined both by
> > ACPI and MPS, we have just started using a different configuration now
> > and an interrupt source override provided by the manufacturer
> > explicitly states INTIN2 is good to use. In a sense you were simply
> > lucky previously the kernel was bad enough with the way it configured
> > the timer through the I/O APIC it failed completely avoiding the bug
> > in your firmware. Now the bug has got uncovered.
>
> well as long as we eliminate the bad effects around via DMI exceptions
> nobody will feel the need to argue whether it's a regression ;-) [this
> problem could be argued to be a regression, even if it's caused by prior
> luck/stupidity of Linux. We have to live with the effects of our
> mistakes.]

Of course -- this is the only reason I can be bothered with the issue in
the first place. Otherwise, I would have said: 'Get the manufacturer to
fix it, use "noapic" or live with a local patch.'

This is actually how I have kept one of my old MPS SMP systems up for
years now -- it has a broken MP table which prevents interrupts from
working when too many PCI option cards are present, so I have prepared a
patch for patching the table manually. I proposed it once, which you may
recall, but it was rejected on the grounds of the syntax being too tough
to comprehend to a poor average user being. I am sure more systems would
benefit as MP table breakages used to be quite common.

Here the simple workaround was "noapic" too, so everyone else could be
happy and I have been happy to keep the patch and use the capabilities of
the piece of hardware properly despite its broken firmware.

Maciej


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