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x86/mm: Fix the size calculation of mapping tables

tip:x86/mm tip-bot for WANG Cong 2 participants 2 messages Mar 6, 2012 – Mar 14, 2012

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#0 lore raw
Commit-ID:  722bc6b16771ed80871e1fd81c86d3627dda2ac8
Gitweb:     http://git.kernel.org/tip/722bc6b16771ed80871e1fd81c86d3627dda2ac8
Author:     WANG Cong <[email protected]>
AuthorDate: Mon, 5 Mar 2012 15:05:13 -0800
Committer:  Ingo Molnar <[email protected]>
CommitDate: Tue, 6 Mar 2012 09:38:26 +0100

x86/mm: Fix the size calculation of mapping tables

For machines that enable PSE, the first 2/4M memory region still uses 4K pages, so needs more PTEs in this case, but find_early_table_space() doesn't count this.

This patch fixes it.

The bug was found via code review, no misbehavior of the kernel was observed.

Signed-off-by WANG Cong <[email protected]>
Cc Yinghai Lu <[email protected]>
Cc Tejun Heo <[email protected]>
Cc <[email protected]>
Signed-off-by Andrew Morton <[email protected]>
Link http://lkml.kernel.org/n/[email protected] open here
Signed-off-by Ingo Molnar <[email protected]>
---
 arch/x86/mm/init.c |   21 ++++++++++++---------
 1 files changed, 12 insertions(+), 9 deletions(-)
arch/x86/mm/init.c +12 -9
index 6cabf65..2e92fdc 100644
@@ -30,8 +30,14 @@ int direct_gbpages
 #endif
 ;
 
-static void __init find_early_table_space(unsigned long end, int use_pse,
-					  int use_gbpages)
+struct map_range {
+	unsigned long start;
+	unsigned long end;
+	unsigned page_size_mask;
+};
+
+static void __init find_early_table_space(struct map_range *mr, unsigned long end,
+					  int use_pse, int use_gbpages)
 {
 	unsigned long puds, pmds, ptes, tables, start = 0, good_end = end;
 	phys_addr_t base;

@@ -56,6 +62,9 @@ static void __init find_early_table_space(unsigned long end, int use_pse,
 #ifdef CONFIG_X86_32
 		extra += PMD_SIZE;
 #endif
+		/* The first 2/4M doesn't use large pages. */
+		extra += mr->end - mr->start;
+
 		ptes = (extra + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	} else
 		ptes = (end + PAGE_SIZE - 1) >> PAGE_SHIFT;

@@ -85,12 +94,6 @@ void __init native_pagetable_reserve(u64 start, u64 end)
 	memblock_reserve(start, end - start);
 }
 
-struct map_range {
-	unsigned long start;
-	unsigned long end;
-	unsigned page_size_mask;
-};
-
 #ifdef CONFIG_X86_32
 #define NR_RANGE_MR 3
 #else /* CONFIG_X86_64 */

@@ -262,7 +265,7 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
 	 * nodes are discovered.
 	 */
 	if (!after_bootmem)
-		find_early_table_space(end, use_pse, use_gbpages);
+		find_early_table_space(&mr[0], end, use_pse, use_gbpages);
 
 	for (i = 0; i < nr_range; i++)
 		ret = kernel_physical_mapping_init(mr[i].start, mr[i].end,
#1 lore raw
Quoted 51 lines · tip-bot for WANG Cong

Commit-ID:  722bc6b16771ed80871e1fd81c86d3627dda2ac8
Gitweb:     http://git.kernel.org/tip/722bc6b16771ed80871e1fd81c86d3627dda2ac8
Author:     WANG Cong <[email protected]>
AuthorDate: Mon, 5 Mar 2012 15:05:13 -0800
Committer:  Ingo Molnar <[email protected]>
CommitDate: Tue, 6 Mar 2012 09:38:26 +0100

x86/mm: Fix the size calculation of mapping tables

For machines that enable PSE, the first 2/4M memory region still uses 4K pages, so needs more PTEs in this case, but find_early_table_space() doesn't count this.

This patch fixes it.

The bug was found via code review, no misbehavior of the kernel was observed.

Signed-off-by WANG Cong <[email protected]>
Cc Yinghai Lu <[email protected]>
Cc Tejun Heo <[email protected]>
Cc <[email protected]>
Signed-off-by Andrew Morton <[email protected]>
Link http://lkml.kernel.org/n/[email protected] open here
Signed-off-by Ingo Molnar <[email protected]>

---
 arch/x86/mm/init.c |   21 ++++++++++++---------

 1 files changed, 12 insertions(+), 9 deletions(-)
arch/x86/mm/init.c +8 -2
index 6cabf65..2e92fdc 100644
@@ -30,8 +30,14 @@ int direct_gbpages
  #endif
  ;
 
-static void __init find_early_table_space(unsigned long end, int use_pse,
-                                         int use_gbpages)
+struct map_range {
+       unsigned long start;
+       unsigned long end;
+       unsigned page_size_mask;
+};
+
+static void __init find_early_table_space(struct map_range *mr, unsigned long end,
+                                         int use_pse, int use_gbpages)
  {
        unsigned long puds, pmds, ptes, tables, start = 0, good_end = end;
        phys_addr_t base;

arch/x86/mm/init.c static void __init find_early_table_space(unsigned long end, int use_pse, · line 67

Quoted 6 lines
arch/x86/mm/init.c +3 -0
@@ -56,6 +62,9 @@ static void __init find_early_table_space(unsigned long end, int use_pse,
  #ifdef CONFIG_X86_32
                extra += PMD_SIZE;
  #endif
+               /* The first 2/4M doesn't use large pages. */
+               extra += mr->end - mr->start;
+

Something wrong here, you need to check if this MR is really cover first 2/4M ...
something like

arch/x86/mm/init.c +2 -1
Index: linux-2.6/arch/x86/mm/init.c
===================================================================
@@ -63,7 +63,8 @@ static void __init find_early_table_spac
 		extra += PMD_SIZE;
 #endif
 		/* The first 2/4M doesn't use large pages. */
-		extra += mr->end - mr->start;
+		if (mr->start < PMD_SIZE)
+			extra += mr->end - mr->start;
 
 		ptes = (extra + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	} else

otherwise, for system with 512G or more. page table for [4G, 512g) may have preallocate more
but only use little.

Yinghai