linux-kernel - [PATCH v2 1/2] x86,mtrr: Fix original mtrr range get for mtrr

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Date:	Sun,  9 Jun 2013 23:28:48 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	Joshua Covington <joshuacov@...glemail.com>,
	linux-kernel@...r.kernel.org, Yinghai Lu <yinghai@...nel.org>,
	<stable@...r.kernel.org>
Subject: [PATCH v2 1/2] x86,mtrr: Fix original mtrr range get for mtrr_cleanup

Joshua reported: Commit cd7b304dfaf1 (x86, range: fix missing merge
during add range) broke mtrr cleanup on his setup in 3.9.5.
corresponding commit in upstream is fbe06b7bae7c.

  *BAD*gran_size: 64K chunk_size: 16M num_reg: 6 lose cover RAM: -0G

https://bugzilla.kernel.org/show_bug.cgi?id=59491

So it rejects new var mtrr layout.

It turns out we have some problem with initial mtrr range retrievel.
current sequence is:
	x86_get_mtrr_mem_range
		==> bunchs of add_range_with_merge
		==> bunchs of subract_range
		==> clean_sort_range
	add_range_with_merge for [0,1M)
	sort_range()

add_range_with_merge could have blank slots, so we can not just
sort only, that will have final result have extra blank slot in head.

So move that calling add_range_with_merge for [0,1M), with that we
could avoid extra clean_sort_range calling.

Reported-by: Joshua Covington <joshuacov@...glemail.com>
Tested-by: Joshua Covington <joshuacov@...glemail.com>
Signed-off-by: Yinghai Lu <yinghai@...nel.org>
Cc: <stable@...r.kernel.org> v3.9

---
 arch/x86/kernel/cpu/mtrr/cleanup.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Index: linux-2.6/arch/x86/kernel/cpu/mtrr/cleanup.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/mtrr/cleanup.c
+++ linux-2.6/arch/x86/kernel/cpu/mtrr/cleanup.c
@@ -714,15 +714,15 @@ int __init mtrr_cleanup(unsigned address
 	if (mtrr_tom2)
 		x_remove_size = (mtrr_tom2 >> PAGE_SHIFT) - x_remove_base;
 
-	nr_range = x86_get_mtrr_mem_range(range, 0, x_remove_base, x_remove_size);
 	/*
 	 * [0, 1M) should always be covered by var mtrr with WB
 	 * and fixed mtrrs should take effect before var mtrr for it:
 	 */
-	nr_range = add_range_with_merge(range, RANGE_NUM, nr_range, 0,
+	nr_range = add_range_with_merge(range, RANGE_NUM, 0, 0,
 					1ULL<<(20 - PAGE_SHIFT));
-	/* Sort the ranges: */
-	sort_range(range, nr_range);
+	/* add from var mtrr at last */
+	nr_range = x86_get_mtrr_mem_range(range, nr_range,
+					  x_remove_base, x_remove_size);
 
 	range_sums = sum_ranges(range, nr_range);
 	printk(KERN_INFO "total RAM covered: %ldM\n",
--
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