Re: [PATCH] x86: set Pentium M as PAE capable

From: "H. Peter Anvin" <hpa@zytor.com>
To: Borislav Petkov <bp@alien8.de>,
	Chris Bainbridge <chris.bainbridge@gmail.com>
Cc: davej@redhat.com, x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86: set Pentium M as PAE capable
Date: Wed, 26 Feb 2014 08:46:14 -0800	[thread overview]
Message-ID: <530E1A56.6060802@zytor.com> (raw)
In-Reply-To: <20140226131852.GA22690@pd.tnic>

On 02/26/2014 05:18 AM, Borislav Petkov wrote:
> On Wed, Feb 26, 2014 at 07:12:59PM +0700, Chris Bainbridge wrote:
>> @@ -226,6 +234,15 @@ static void intel_workarounds(struct cpuinfo_x86 *c)
>>  		clear_cpu_cap(c, X86_FEATURE_SEP);
>>  
>>  	/*
>> +	 * PAE CPUID bug: Pentium M reports no PAE but has PAE
>> +	 */
>> +	if (forcepae) {
>> +		printk(KERN_WARNING "PAE forced!\n");
>> +		set_cpu_cap(c, X86_FEATURE_PAE);
>> +		add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE);
> 
> This is certainly the wrong taint flag. We'd need a new one or to
> repurpose another one as I suggested in a previous mail.
> 

I liked your proposal:

> Right, I was about to say that. And since there's no special bit for
> running "out-of-spec", we could probably repurpose
> 
> TAINT_UNSAFE_SMP - 'S' - SMP with CPUs not designed for SMP.
> 
> to
> 
> TAINT_UNSAFE_OUT_OF_SPEC (the letter S fits still) and add that taint
> everytime we're enforcing functionality against doctor's orders, so to
> speak. 

	-hpa