linux-kernel - [PATCH 1/2] x86: Cleanup highmap after brk is concluded

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Date:	Mon, 28 Feb 2011 18:25:16 +0000
From:	stefano.stabellini@...citrix.com
To:	linux-kernel@...r.kernel.org
Cc:	xen-devel@...ts.xensource.com, hpa@...or.com,
	konrad.wilk@...cle.com, yinghai@...nel.org, jeremy@...p.org,
	Stefano.Stabellini@...citrix.com,
	Stefano Stabellini <stefano.stabellini@...citrix.com>
Subject: [PATCH 1/2] x86: Cleanup highmap after brk is concluded

From: Yinghai Lu <yinghai@...nel.org>

Now cleanup_highmap actually is in two steps: one is early in head64.c
and only clears above _end; a second one is in init_memory_mapping() and
tries to clean from _brk_end to _end.
It should check if those boundaries are PMD_SIZE aligned but currently
does not.
Also init_memory_mapping() is called several times for numa or memory
hotplug, so we really should not handle initial kernel mappings there.

This patch moves cleanup_highmap() down after _brk_end is settled so
we can do everything in one step.
Also we honor max_pfn_mapped in the implementation of cleanup_highmap.

Signed-off-by: Yinghai Lu <yinghai@...nel.org>
Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
---
 arch/x86/kernel/head64.c |    3 ---
 arch/x86/kernel/setup.c  |    6 ++++++
 arch/x86/mm/init.c       |   19 -------------------
 arch/x86/mm/init_64.c    |   11 ++++++-----
 4 files changed, 12 insertions(+), 27 deletions(-)

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 2d2673c..5655c22 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -77,9 +77,6 @@ void __init x86_64_start_kernel(char * real_mode_data)
 	/* Make NULL pointers segfault */
 	zap_identity_mappings();
 
-	/* Cleanup the over mapped high alias */
-	cleanup_highmap();
-
 	max_pfn_mapped = KERNEL_IMAGE_SIZE >> PAGE_SHIFT;
 
 	for (i = 0; i < NUM_EXCEPTION_VECTORS; i++) {
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index d3cfe26..f03e6e0 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -297,6 +297,9 @@ static void __init init_gbpages(void)
 static inline void init_gbpages(void)
 {
 }
+static void __init cleanup_highmap(void)
+{
+}
 #endif
 
 static void __init reserve_brk(void)
@@ -922,6 +925,9 @@ void __init setup_arch(char **cmdline_p)
 	 */
 	reserve_brk();
 
+	/* Cleanup the over mapped high alias after _brk_end*/
+	cleanup_highmap();
+
 	memblock.current_limit = get_max_mapped();
 	memblock_x86_fill();
 
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 947f42a..f13ff3a 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -279,25 +279,6 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
 	load_cr3(swapper_pg_dir);
 #endif
 
-#ifdef CONFIG_X86_64
-	if (!after_bootmem && !start) {
-		pud_t *pud;
-		pmd_t *pmd;
-
-		mmu_cr4_features = read_cr4();
-
-		/*
-		 * _brk_end cannot change anymore, but it and _end may be
-		 * located on different 2M pages. cleanup_highmap(), however,
-		 * can only consider _end when it runs, so destroy any
-		 * mappings beyond _brk_end here.
-		 */
-		pud = pud_offset(pgd_offset_k(_brk_end), _brk_end);
-		pmd = pmd_offset(pud, _brk_end - 1);
-		while (++pmd <= pmd_offset(pud, (unsigned long)_end - 1))
-			pmd_clear(pmd);
-	}
-#endif
 	__flush_tlb_all();
 
 	if (!after_bootmem && e820_table_end > e820_table_start)
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 71a5929..a8d08c2 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -51,6 +51,7 @@
 #include <asm/numa.h>
 #include <asm/cacheflush.h>
 #include <asm/init.h>
+#include <asm/setup.h>
 
 static int __init parse_direct_gbpages_off(char *arg)
 {
@@ -293,18 +294,18 @@ void __init init_extra_mapping_uc(unsigned long phys, unsigned long size)
  * to the compile time generated pmds. This results in invalid pmds up
  * to the point where we hit the physaddr 0 mapping.
  *
- * We limit the mappings to the region from _text to _end.  _end is
- * rounded up to the 2MB boundary. This catches the invalid pmds as
+ * We limit the mappings to the region from _text to _brk_end.  _brk_end
+ * is rounded up to the 2MB boundary. This catches the invalid pmds as
  * well, as they are located before _text:
  */
 void __init cleanup_highmap(void)
 {
 	unsigned long vaddr = __START_KERNEL_map;
-	unsigned long end = roundup((unsigned long)_end, PMD_SIZE) - 1;
+	unsigned long vaddr_end = __START_KERNEL_map + (max_pfn_mapped << PAGE_SHIFT);
+	unsigned long end = roundup((unsigned long)_brk_end, PMD_SIZE) - 1;
 	pmd_t *pmd = level2_kernel_pgt;
-	pmd_t *last_pmd = pmd + PTRS_PER_PMD;
 
-	for (; pmd < last_pmd; pmd++, vaddr += PMD_SIZE) {
+	for (; vaddr + PMD_SIZE - 1 < vaddr_end; pmd++, vaddr += PMD_SIZE) {
 		if (pmd_none(*pmd))
 			continue;
 		if (vaddr < (unsigned long) _text || vaddr > end)
-- 
1.5.6.5

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