Re: [RFC/PATCH] Kdump: Disabling PCI interrupts in capture kernel

[Alan Stern <stern@rowland.harvard.edu>]

On Sat, 4 Jun 2005, Vivek Goyal wrote:

> Hi Alan, I know very little about consoles and their working.
> I had a question. Even if console is being managed by platform firmware, in
> initial states of booting, does it require interrupts to be enabled at 
> VGA contorller (at least for the simple text mode). I was quickly browsing
> through drivers/video/console/vgacon.c and did not look like that this
> console driver needed interrupts to be enabled at the controller.

This isn't an issue for VGA, as far as I know.  It applies to
architectures like PPC-64 and perhaps Alpha or PA-Risc.  And I don't know
the details; ask Grant Grundler.

> Anyway, looks like serial consoles will always work. So at least this can be
> done for kdump case (CONFIG_CRASH_DUMP) and not generic kernel. Or, as I
> mentioned in previous mail, while pre-loading capture kernel, pass a command
> line parameter containing pci dev id of console and capture kernel does not 
> disable interrupts on this console.  

I suspect you're right that implementing this only in kdump kernels will 
work okay.

For people interesting in reading some old threads on the subject, here 
are some pointers:

http://marc.theaimsgroup.com/?l=linux-usb-devel&m=111055702309788&w=2

http://marc.theaimsgroup.com/?l=linux-kernel&m=98383052711171&w=2

Alan Stern

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