linux-kernel - Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover from machine checks

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Date:	Sun, 27 Dec 2015 14:33:30 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Tony Luck <tony.luck@...il.com>,
	linux-nvdimm <linux-nvdimm@...1.01.org>, X86 ML <x86@...nel.org>,
	"elliott@....com" <elliott@....com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Williams, Dan J" <dan.j.williams@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover
 from machine checks

On Sun, Dec 27, 2015 at 05:25:45AM -0800, Andy Lutomirski wrote:
> That could significantly bloat the kernel image.

Yeah, we probably should build an allyesconfig and see how big
__ex_table is and compute how much actually that bloat would be,
because...

> Anyway, the bit 31 game isn't so bad IMO because it's localized to the
> extable macros and the extable reader, whereas the bit 63 thing is all
> tangled up with the __mcsafe_copy thing, and that's just the first
> user of a more general mechanism.
> 
> Did you see this:
> 
> https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/commit/?h=strict_uaccess_fixups/patch_v1&id=16644d9460fc6531456cf510d5efc57f89e5cd34

... the problem this has is that you have 4 classes, AFAICT. And since
we're talking about a generic mechanism, the moment the 4 classes are
not enough, this new scheme fails.

I'm just saying...

4 classes are probably more than enough but we don't know.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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