[PATCH 2/2] Use page present for pae pdpes

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Date:	Wed, 31 Aug 2005 14:51:48 -0700
To: Andrew Morton <akpm@osdl.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Virtualization Mailing List <virtualization@lists.osdl.org>, "H. Peter Anvin" <hpa@zytor.com>, Zwane Mwaikambo <zwane@arm.linux.org.uk>, Chris Wright <chrisw@osdl.org>, Martin Bligh <mbligh@mbligh.org>, Pratap Subrahmanyam <pratap@vmware.com>, Christopher Li <chrisl@vmware.com>, Zachary Amsden <zach@vmware.com>, Zachary Amsden <zach@vmware.com>

Ok, the use of "1 + " and subtraction of one for PAE PDPEs has confused
many people now. Make it explicit what is going on and why anding with
PAGE_MASK is a better idea to strip these bits.

Signed-off-by: Zachary Amsden <zach@vmware.com>
Depends-on: add-pgtable-allocation-notifiers
Index: linux-2.6.13/arch/i386/mm/pgtable.c
===================================================================
--- linux-2.6.13.orig/arch/i386/mm/pgtable.c 2005-08-31 14:48:17.000000000 -0700
+++ linux-2.6.13/arch/i386/mm/pgtable.c 2005-08-31 14:48:53.000000000 -0700
@@ -247,14 +247,14 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
                 if (!pmd)
                         goto out_oom;
                 SetPagePDE(virt_to_page(pmd));
- set_pgd(&pgd[i], __pgd(1 + __pa(pmd)));
+ set_pgd(&pgd[i], __pgd(_PAGE_PRESENT | __pa(pmd)));
         }
         return pgd;
 
 out_oom:
         for (i--; i >= 0; i--) {
                 ClearPagePDE(pfn_to_page(pgd_val(pgd[i]) >> PAGE_SHIFT));
- kmem_cache_free(pmd_cache, (void *)__va(pgd_val(pgd[i])-1));
+ kmem_cache_free(pmd_cache, (void *)__va(pgd_val(pgd[i]) & PAGE_MASK));
         }
         kmem_cache_free(pgd_cache, pgd);
         return NULL;
@@ -268,7 +268,7 @@ void pgd_free(pgd_t *pgd)
         if (PTRS_PER_PMD > 1)
                 for (i = 0; i < USER_PTRS_PER_PGD; ++i) {
                         ClearPagePDE(pfn_to_page(pgd_val(pgd[i]) >> PAGE_SHIFT));
- kmem_cache_free(pmd_cache, (void *)__va(pgd_val(pgd[i])-1));
+ kmem_cache_free(pmd_cache, (void *)__va(pgd_val(pgd[i]) & PAGE_MASK));
                 }
         /* in the non-PAE case, free_pgtables() clears user pgd entries */
         kmem_cache_free(pgd_cache, pgd);
Index: linux-2.6.13/arch/i386/mm/init.c
===================================================================
--- linux-2.6.13.orig/arch/i386/mm/init.c 2005-08-31 14:48:17.000000000 -0700
+++ linux-2.6.13/arch/i386/mm/init.c 2005-08-31 14:48:53.000000000 -0700
@@ -387,7 +387,7 @@ void zap_low_mappings (void)
          */
         for (i = 0; i < USER_PTRS_PER_PGD; i++)
 #ifdef CONFIG_X86_PAE
- set_pgd(swapper_pg_dir+i, __pgd(1 + __pa(empty_zero_page)));
+ set_pgd(swapper_pg_dir+i, __pgd(_PAGE_PRESENT | __pa(empty_zero_page)));
 #else
                 set_pgd(swapper_pg_dir+i, __pgd(0));
 #endif
-
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• Previous message: Jim Keniston: "[PATCH] Fix kprobes handling of simultaneous probe hit/unregister"
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