linux-kernel - Re: [PATCH 1/3] e820: Don't let unknown DIMM type come out BUSY

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Message-ID: <CAPcyv4hNJO+2S7-H52CY7PjCVx46=OC0OMqO09vO-WB0MFVM-g@mail.gmail.com>
Date:	Wed, 25 Feb 2015 18:09:01 -0800
From:	Dan Williams <dan.j.williams@...el.com>
To:	Boaz Harrosh <boaz@...xistor.com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	X86 ML <x86@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"Roger C. Pao" <rcpao.enmotus@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-nvdimm <linux-nvdimm@...ts.01.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Matthew Wilcox <willy@...ux.intel.com>,
	Andy Lutomirski <luto@...capital.net>,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH 1/3] e820: Don't let unknown DIMM type come out BUSY

On Mon, Feb 23, 2015 at 11:59 PM, Boaz Harrosh <boaz@...xistor.com> wrote:
> No, this is a complete HACK, since when do we hard code specific (GLOBAL)
> ARCHs strings in common code. Please look at linux/ioport.h see the richness
> of options for all kind of buses and systems. The flag system works perfectly
> and I just continue this here.
>
> And really DAN, you prefer a global string that's dead garbage in 99% of arches
> to a simple bit flag definition that costs nothing? I don't think so.

Glad we're moving ahead with the IORESOURCE_MEM_WARN solution rather
than this or the 64-bit-limited IORESOURCE_WARN approach.

>
>> +             add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
>
> NACK!!
>

I disagree.  Ultimately what goes into kernel/resource.c is not up to
me, but firmware/driver combinations that subvert standards should be
flagged by the kernel.  Stepping back from the original motivation, in
the general case, an unknown memory type is indiscernible from a BIOS
bug.

TAINT_FIRMWARE_WORKAROUND is simply a notification that firmware needs
to be updated, and I believe a driver attaching to unknown memory is
such an event.  It does not block a user from using that memory
however he or she sees fit.
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