linux-kernel - Re: [PATCHV3 1/3] x86, ras: Add new infrastructure for machine check fixup tables

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Date:	Mon, 21 Dec 2015 11:16:44 -0800
From:	Dan Williams <dan.j.williams@...el.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Tony Luck <tony.luck@...el.com>, Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>, Elliott@...tnic,
	Robert <elliott@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux MM <linux-mm@...ck.org>,
	linux-nvdimm <linux-nvdimm@...1.01.org>, X86 ML <x86@...nel.org>
Subject: Re: [PATCHV3 1/3] x86, ras: Add new infrastructure for machine check
 fixup tables

On Mon, Dec 21, 2015 at 10:18 AM, Borislav Petkov <bp@...en8.de> wrote:
> On Tue, Dec 15, 2015 at 05:29:30PM -0800, Tony Luck wrote:
>> Copy the existing page fault fixup mechanisms to create a new table
>> to be used when fixing machine checks. Note:
>> 1) At this time we only provide a macro to annotate assembly code
>> 2) We assume all fixups will in code builtin to the kernel.
>> 3) Only for x86_64
>> 4) New code under CONFIG_MCE_KERNEL_RECOVERY (default 'n')
>>
>> Signed-off-by: Tony Luck <tony.luck@...el.com>
>> ---
>>  arch/x86/Kconfig                  | 10 ++++++++++
>>  arch/x86/include/asm/asm.h        | 10 ++++++++--
>>  arch/x86/include/asm/mce.h        | 14 ++++++++++++++
>>  arch/x86/kernel/cpu/mcheck/mce.c  | 16 ++++++++++++++++
>>  arch/x86/kernel/vmlinux.lds.S     |  6 +++++-
>>  arch/x86/mm/extable.c             | 19 +++++++++++++++++++
>>  include/asm-generic/vmlinux.lds.h | 12 +++++++-----
>>  7 files changed, 79 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>> index 96d058a87100..42d26b4d1ec4 100644
>> --- a/arch/x86/Kconfig
>> +++ b/arch/x86/Kconfig
>> @@ -1001,6 +1001,16 @@ config X86_MCE_INJECT
>>         If you don't know what a machine check is and you don't do kernel
>>         QA it is safe to say n.
>>
>> +config MCE_KERNEL_RECOVERY
>> +     bool "Recovery from machine checks in special kernel memory copy functions"
>> +     default n
>> +     depends on X86_MCE && X86_64
>
> Still no dependency on CONFIG_LIBNVDIMM.

I suggested we reverse the dependency and have the driver optionally
"select MCE_KERNEL_RECOVERY".  There may be other drivers outside of
LIBNVDIMM that want this functionality enabled.
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