linux-kernel - [PATCH x86/mm] x86-64, NUMA: Fix distance table handling

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Message-ID: <20110302100400.GK19669@htj.dyndns.org>
Date:	Wed, 2 Mar 2011 11:04:00 +0100
From:	Tejun Heo <tj@...nel.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Yinghai Lu <yinghai@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	tglx@...utronix.de, "H. Peter Anvin" <hpa@...or.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH x86/mm] x86-64, NUMA: Fix distance table handling

>From dcd414c795a28fff6e511d58e4cfd1202323c703 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@...nel.org>
Date: Wed, 2 Mar 2011 10:54:10 +0100

NUMA distance table handling has the following problems.

* numa_reset_distance() uses numa_distance * sizeof(numa_distance[0])
  as the table size when it should be using the square of
  numa_distance.

* The same size miscalculation when allocation space for phys_dist in
  numa_emulation().

* In numa_emulation(), phys_dist must be reserved; otherwise, the new
  emulated distance table may overlap it.

Fix them and, while at it, take numa_distance_cnt resetting in
numa_reset_distance() out of the if block to simplify the code a bit.

David Rientjes reported incorrect handling of distance table during
emulation and Yinghai identified the above problems and wrote the
original patch to fix the problems.  This patch is based on Yinghai's
patch.

Reported-by: David Rientjes <rientjes@...gle.com>
Patch-originally-from: Yinghai Lu <yinghai@...nel.org>
Signed-off-by: Tejun Heo <tj@...nel.org>
---
David, can you please verify whether this patch fixes the problem?
Thanks.

 arch/x86/mm/numa_64.c        |    9 ++++-----
 arch/x86/mm/numa_emulation.c |   16 ++++++++++------
 2 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/arch/x86/mm/numa_64.c b/arch/x86/mm/numa_64.c
index cccc01d..a94f12c 100644
--- a/arch/x86/mm/numa_64.c
+++ b/arch/x86/mm/numa_64.c
@@ -390,14 +390,13 @@ static void __init numa_nodemask_from_meminfo(nodemask_t *nodemask,
  */
 void __init numa_reset_distance(void)
 {
-	size_t size;
+	size_t size = numa_distance_cnt * numa_distance_cnt *
+		      sizeof(numa_distance[0]);
 
-	if (numa_distance_cnt) {
-		size = numa_distance_cnt * sizeof(numa_distance[0]);
+	if (numa_distance_cnt)
 		memblock_x86_free_range(__pa(numa_distance),
 					__pa(numa_distance) + size);
-		numa_distance_cnt = 0;
-	}
+	numa_distance_cnt = 0;
 	numa_distance = NULL;
 }
 
diff --git a/arch/x86/mm/numa_emulation.c b/arch/x86/mm/numa_emulation.c
index 607a2e8..50fda06 100644
--- a/arch/x86/mm/numa_emulation.c
+++ b/arch/x86/mm/numa_emulation.c
@@ -300,6 +300,7 @@ void __init numa_emulation(struct numa_meminfo *numa_meminfo, int numa_dist_cnt)
 	static struct numa_meminfo pi __initdata;
 	const u64 max_addr = max_pfn << PAGE_SHIFT;
 	u8 *phys_dist = NULL;
+	size_t phys_size = numa_dist_cnt * numa_dist_cnt * sizeof(phys_dist[0]);
 	int i, j, ret;
 
 	if (!emu_cmdline)
@@ -336,21 +337,19 @@ void __init numa_emulation(struct numa_meminfo *numa_meminfo, int numa_dist_cnt)
 		goto no_emu;
 	}
 
-	/*
-	 * Copy the original distance table.  It's temporary so no need to
-	 * reserve it.
-	 */
+	/* copy the physical distance table */
 	if (numa_dist_cnt) {
-		size_t size = numa_dist_cnt * sizeof(phys_dist[0]);
 		u64 phys;
 
 		phys = memblock_find_in_range(0,
 					      (u64)max_pfn_mapped << PAGE_SHIFT,
-					      size, PAGE_SIZE);
+					      phys_size, PAGE_SIZE);
 		if (phys == MEMBLOCK_ERROR) {
 			pr_warning("NUMA: Warning: can't allocate copy of distance table, disabling emulation\n");
 			goto no_emu;
 		}
+		memblock_x86_reserve_range(phys, phys + phys_size,
+					   "TMP NUMA DIST");
 		phys_dist = __va(phys);
 
 		for (i = 0; i < numa_dist_cnt; i++)
@@ -398,6 +397,11 @@ void __init numa_emulation(struct numa_meminfo *numa_meminfo, int numa_dist_cnt)
 			numa_set_distance(i, j, dist);
 		}
 	}
+
+	/* free the copied physical distance table */
+	if (phys_dist)
+		memblock_x86_free_range(__pa(phys_dist),
+					__pa(phys_dist) + phys_size);
 	return;
 
 no_emu:
-- 
1.7.1

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