linux-kernel - Re: [RFC] amd64_edac: syndromes loading

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Message-ID: <20091105221725.GA3683@elf.ucw.cz>
Date:	Thu, 5 Nov 2009 23:17:25 +0100
From:	Pavel Machek <pavel@....cz>
To:	Borislav Petkov <borislav.petkov@....com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Doug Thompson <norsk5@...oo.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>, x86 <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] amd64_edac: syndromes loading

Hi!

> sorry for the delay, I had to talk to the hardware guys about those
> tables.
> 
> On Mon, Nov 02, 2009 at 07:33:14AM +0900, H. Peter Anvin wrote:
> > >>Alternatively, we could make the syndromes builtin thus removing the
> > >>requirement to go to userspace for the loading. For that we'll need
> > >>two new .c files in drivers/edac/ which represent the x4 and x8 tables
> > >>respectively:
> > >>
> > >>unsigned short x8_raw_data[] = {
> > >>         0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
> > >>         0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000,
> > >>         0x0000, 0x0100, 0x0001, 0x0101, 0x01B8, 0x015C, 0x012E, 0x01C6, 0x0163,
> > >>         0x01FD, 0x0189, 0x019D, 0xB801, 0x5C01, 0x2E01, 0xC601, 0x6301, 0xFD01,
> > >>         0x8901, 0x9D01, 0x0200, 0x0002, 0x0202, 0x0201, 0x02B8, 0x025C, 0x02FD,
> > >>	....
> > >>
> > >>The drawback with these is that they'll always be builtin, enlarging
> > >>kernel code by 10-15K although only one of them is in use.
> > >
> > >I believe that 15K is reasonable price to pay for not having to
> > >install another 'firmware' file.
> > 
> > a) aren't these computable somehow?  If so, it's probably easier to
> > include the algorithm in the kernel rather than a table.
> 
> That's a no-go since it would involve IP disclosure.

Then you should really talk to the lawyers. Is AMD willing to risk GPL
violation by merging something other than "form preferable for
editing"?

> > b) "I believe that 15K is reasonable price to pay for not having to
> > install another 'firmware' file."  I think that's a tradeoff a lot
> > of people would *not* choose to make.  This is of course why we have
> > (or at least, should have) to either compile in firmware blobs or
> > not.
> 
> The good news is they've come up with a modified algorithm which will
> require a smaller table, roughly 1/4th the size of the current 10K one.
> Now, on a second thought and IMHO, we should simply add another .c file
> instantiating those two x4 and x8 tables statically and linking them
> into the edac code. This way you
> 
> 1) don't have the additional complexity of adding firmware handling code
> and thus don't add a dependency on the firmware API
> 
> 2) don't have to actually carry two firmware images with the kernel

Well, that's certainly better than current situation.

									Pavel

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