linux-kernel - Re: [PATCH v3 3/5] mtrr, x86: Fix MTRR state checks in mtrr_type

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Date:	Mon, 16 Mar 2015 21:08:16 +0000
From:	"Kani, Toshimitsu" <toshi.kani@...com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"hpa@...or.com" <hpa@...or.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"dave.hansen@...el.com" <dave.hansen@...el.com>,
	"Elliott, Robert (Server Storage)" <Elliott@...com>,
	"pebolle@...cali.nl" <pebolle@...cali.nl>
Subject: Re: [PATCH v3 3/5] mtrr, x86: Fix MTRR state checks in
 mtrr_type_lookup()

> On Mar 16, 2015, at 3:51 AM, Ingo Molnar <mingo@...nel.org> wrote:
> 
> 
> * Toshi Kani <toshi.kani@...com> wrote:
> 
>> 'mtrr_state.enabled' contains FE (fixed MTRRs enabled) and
>> E (MTRRs enabled) flags in MSR_MTRRdefType.  Intel SDM,
>> section 11.11.2.1, defines these flags as follows:
>> - All MTRRs are disabled when the E flag is clear.
>>   The FE flag has no affect when the E flag is clear.
>> - The default type is enabled when the E flag is set.
>> - MTRR variable ranges are enabled when the E flag is set.
>> - MTRR fixed ranges are enabled when both E and FE flags
>>   are set.
>> 
>> MTRR state checks in __mtrr_type_lookup() do not follow the
>> SDM definitions.  Therefore, this patch fixes the MTRR state
>> checks according to the SDM.  This patch defines the flags
>> in mtrr_state.enabled as follows.  print_mtrr_state() is also
>> updated.
>> - FE flag: MTRR_STATE_MTRR_FIXED_ENABLED
>> - E  flag: MTRR_STATE_MTRR_ENABLED
>> 
>> Lastly, this patch fixes the 'else if (start < 0x1000000)',
>> which checks a fixed range but has an extra-zero in the
>> address, to 'else' with no condition.
> 
> Firstly, this does multiple bug fixes in a single patch, which is a 
> no-no: please split it up into separate patches.

Right.  I will split into two patches.

> Secondly, please also outline the differences between the old code and 
> the new code - don't just list the SDM logic and state that we are 
> updating to it.

Yes, I will update the patch log accordingly.

Thanks,
-Toshi

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