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Date: Sun, 27 Dec 2015 11:04:24 -0800
Message-ID: <CAPcyv4j9=OtEpsPwnCFLdUEJxCp5aUhaT5tP5k1n0TRiNbZi8Q@mail.gmail.com>
Subject: Re: [PATCHV5 3/3] x86, ras: Add __mcsafe_copy() function to recover
 from machine checks
From: Dan Williams <dan.j.williams@intel.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>, Tony Luck <tony.luck@gmail.com>,
        linux-nvdimm <linux-nvdimm@ml01.01.org>, X86 ML <x86@kernel.org>,
        "elliott@hpe.com" <elliott@hpe.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Ingo Molnar <mingo@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Sun, Dec 27, 2015 at 5:33 AM, Borislav Petkov <bp@alien8.de> wrote:
> 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.

Then we add support for more than 4 when/if the time comes...
--
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