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 08:51:39 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Toshi Kani <toshi.kani@...com>
Cc:	akpm@...ux-foundation.org, hpa@...or.com, tglx@...utronix.de,
	mingo@...hat.com, linux-mm@...ck.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, dave.hansen@...el.com,
	Elliott@...com, pebolle@...cali.nl
Subject: Re: [PATCH v3 3/5] mtrr, x86: Fix MTRR state checks in
 mtrr_type_lookup()


* 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.

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.

Thanks,

	Ingo
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