From: "Luck, Tony" <tony.luck@intel.com>
To: Borislav Petkov <bp@alien8.de>
CC: Ingo Molnar <mingo@kernel.org>, Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>,
        "Williams, Dan J" <dan.j.williams@intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-nvdimm@ml01.01.org" <linux-nvdimm@ml01.01.org>,
        "x86@kernel.org" <x86@kernel.org>
Subject: RE: [PATCHV2 2/3] x86, ras: Extend machine check recovery code to
 annotated ring0 areas
Thread-Topic: [PATCHV2 2/3] x86, ras: Extend machine check recovery code to
 annotated ring0 areas
Thread-Index: AQHRNy3VWd7zJHLLfUmdzBfwI2jiqJ7MtWLQ
Date: Tue, 15 Dec 2015 23:46:03 +0000
Message-ID: <3908561D78D1C84285E8C5FCA982C28F39F85DBE@ORSMSX114.amr.corp.intel.com>
References: <cover.1449861203.git.tony.luck@intel.com>
 <e8029c58c7d4b5094ec274c78dee01d390317d4d.1449861203.git.tony.luck@intel.com>
 <20151215114314.GD25973@pd.tnic>
In-Reply-To: <20151215114314.GD25973@pd.tnic>
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>> +	/* Fault was in recoverable area of the kernel */
>> +	if ((m.cs & 3) != 3 && worst == MCE_AR_SEVERITY)
>> +		if (!fixup_mcexception(regs, m.addr))
>> +			mce_panic("Failed kernel mode recovery", &m, NULL);
>				   ^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> Does that always imply a failed kernel mode recovery? I don't see
>
>	(m.cs == 0 and MCE_AR_SEVERITY)
>
> MCEs always meaning that a recovery should be attempted there. I think
> this should simply say
>
>	mce_panic("Fatal machine check on current CPU", &m, msg);

I don't think this can ever happen. If we were in kernel mode and decided
that the severity was AR_SEVERITY ... then search_mcexception_table()
found an entry for the IP where the machine check happened.

The only way for fixup_exception to fail is if search_mcexception_table()
now suddenly doesn't find the entry it found earlier.

But if this "can't happen" thing actually does happen ... I'd like the panic
message to be different from other mce_panic() so you'll know to blame
me.

Applied all the other suggestions.

-Tony

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