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

From: Zachary Amsden (zach_at_vmware.com)
Date: 08/31/05

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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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