linux-kernel - Re: [PATCH v8 3/3] x86, mce: Add __mcsafe

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Date:	Sun, 10 Jan 2016 12:26:35 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Tony Luck <tony.luck@...il.com>
Cc:	Dan Williams <dan.j.williams@...el.com>,
	Andy Lutomirski <luto@...capital.net>,
	linux-nvdimm <linux-nvdimm@...1.01.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Robert <elliott@....com>, Ingo Molnar <mingo@...nel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, X86 ML <x86@...nel.org>
Subject: Re: [PATCH v8 3/3] x86, mce: Add __mcsafe_copy()

On Sat, Jan 09, 2016 at 05:40:05PM -0800, Tony Luck wrote:
> BUT ... it's all going to be very messy.  We don't have any CPUID
> capability bits to say whether we support recovery, or which instructions
> are good/bad choices for recovery.

We can always define synthetic ones and set them after having checked
MCA capability bits, f/m/s, etc., maybe even based on the list you're
supplying...

> Linux code recently got some recovery bits for AMD cpus ... I don't
> know what the story is on which models support this,

You mean this?

                /*
                 * overflow_recov is supported for F15h Models 00h-0fh
                 * even though we don't have a CPUID bit for it.
                 */
                if (c->x86 == 0x15 && c->x86_model <= 0xf)
                        mce_flags.overflow_recov = 1;

If so, that's just an improvement which makes MCi_STATUS[Overflow] MCEs
non-fatal.

-- 
Regards/Gruss,
    Boris.

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