linux-kernel - [PATCH] [1/2] Fix some inaccurate comments in MTRR checking code

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Date:	Sat, 19 Jan 2008 05:32:18 +0100 (CET)
From:	Andi Kleen <ak@...e.de>
To:	davej@...emonkey.org.uk, mingo@...e.hu, tglx@...utronix.de,
	jesse.barnes@...el.com, andreas.herrmann3@....com,
	linux-kernel@...r.kernel.org
Subject: [PATCH] [1/2] Fix some inaccurate comments in MTRR checking code


- is_cpu(INTEL) actually refers only to the MTRR architecture
and all AMD CPUs since K7 use the Intel MTRR architecture so the
fixup code runs on AMD too. Remove a comment claiming otherwise.

[Perhaps is_cpu should be renamed, the name is clearly confusing]

- Clarify another incorrect comment.

Cc: davej@...emonkey.org.uk
Signed-off-by: Andi Kleen <ak@...e.de>

---
 arch/x86/kernel/cpu/mtrr/main.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux/arch/x86/kernel/cpu/mtrr/main.c
===================================================================
--- linux.orig/arch/x86/kernel/cpu/mtrr/main.c
+++ linux/arch/x86/kernel/cpu/mtrr/main.c
@@ -640,6 +640,8 @@ early_param("disable_mtrr_trim", disable
  * Some buggy BIOSes don't setup the MTRRs properly for systems with certain
  * memory configurations.  This routine checks to make sure the MTRRs having
  * a write back type cover all of the memory the kernel is intending to use.
+ * [AK: actually it doesn't check that. It just checks that the highest
+ * MTRR is matching the end of memory. That is not quite the same.]
  * If not, it'll trim any memory off the end by adjusting end_pfn, removing
  * it from the kernel's allocation pools, warning the user with an obnoxious
  * message.
@@ -649,7 +651,6 @@ void __init mtrr_trim_uncached_memory(vo
 	unsigned long i, base, size, highest_addr = 0, def, dummy;
 	mtrr_type type;
 
-	/* Make sure we only trim uncachable memory on Intel machines */
 	rdmsr(MTRRdefType_MSR, def, dummy);
 	def &= 0xff;
 	if (!is_cpu(INTEL) || disable_mtrr_trim || def != MTRR_TYPE_UNCACHABLE)
--
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