Re: [PATCH] apci: dump slit

Pavel Machek
2008-09-14T15:59:51Z

On Sun 2008-09-14 14:26:18, Ingo Molnar wrote:
>
> * Pavel Machek <pavel@suse.cz> wrote:
>
> > On Fri 2008-09-12 23:19:21, Thomas Gleixner wrote:
> > > On Fri, 12 Sep 2008, Andi Kleen wrote:
> > > > "Yinghai Lu" <yhlu.kernel@gmail.com> writes:
> > > > >
> > > > > to see how wrong could be set by BIOS.
> > > >
> > > > Just dump it from user space then. There are plenty of tools
> > > > to access ACPI tables.
> > >
> > > 1.) what guarantees that we reach user space ?
> >
> > We can dump in *any* kernel.
> >
> > > 2) If it is _valuable_ information which we can gather via kernel
> > > output, then it is much more conveniant than asking the user to type
> > > whatevercryptictoolcommandline and provide the output.
> >
> > Ooh, 'lets dump more junk at everyone, typing commands is hard' :-(.
>
> no, the principle is, information like the boot-time CPUID information
> (and even the BIOS environment) can be indicative of _kernel bugs_. It
> is often essential to dump what the booting (and failing) kernel thinks
> is its environment.
>
> Often that environment is corrupted (by the kernel) and that leads to
> problems. This 'environment' can also be affected by things like hard
> boot vs cold boot differences, whether it's in a kexec environment,
> whether it's booted as a virtual guest, etc., etc.
>
> For a long time we had the kernel's x86 bootup pretty much as a mostly
> silent black box and when it broke we tried to figure things out
> afterwards which was difficult and error-prone. Now we've got various
> quite effective debug mechanisms (which includes printouts as well) and
> figuring out x86 problems is visibly easier. We definitely wont go back
> to the 'black box code, can only be debugged by a few experts' method.
>
> So extending on that is a good and obvious idea in general - and i agree
> with Peter that this should be command-line dependent, i.e. not printed
> by default. Only printing it when 'debug' is specified on the command
> line is a good solution.

Dumping when user requested it on commandline seems like good
compromise to me.
Pavel
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