Merge tag 'v4.0-rc1' into x86/mm, to refresh the tree

[cascardo/linux.git] / arch / x86 / mm / pgtable.c

diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 7b22ada..5a7e525 100644 (file)
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -275,12 +275,87 @@ static void pgd_prepopulate_pmd(struct mm_struct *mm, pgd_t *pgd, pmd_t *pmds[])
        }
 }
 
+/*
+ * Xen paravirt assumes pgd table should be in one page. 64 bit kernel also
+ * assumes that pgd should be in one page.
+ *
+ * But kernel with PAE paging that is not running as a Xen domain
+ * only needs to allocate 32 bytes for pgd instead of one page.
+ */
+#ifdef CONFIG_X86_PAE
+
+#include <linux/slab.h>
+
+#define PGD_SIZE       (PTRS_PER_PGD * sizeof(pgd_t))
+#define PGD_ALIGN      32
+
+static struct kmem_cache *pgd_cache;
+
+static int __init pgd_cache_init(void)
+{
+       /*
+        * When PAE kernel is running as a Xen domain, it does not use
+        * shared kernel pmd. And this requires a whole page for pgd.
+        */
+       if (!SHARED_KERNEL_PMD)
+               return 0;
+
+       /*
+        * when PAE kernel is not running as a Xen domain, it uses
+        * shared kernel pmd. Shared kernel pmd does not require a whole
+        * page for pgd. We are able to just allocate a 32-byte for pgd.
+        * During boot time, we create a 32-byte slab for pgd table allocation.
+        */
+       pgd_cache = kmem_cache_create("pgd_cache", PGD_SIZE, PGD_ALIGN,
+                                     SLAB_PANIC, NULL);
+       if (!pgd_cache)
+               return -ENOMEM;
+
+       return 0;
+}
+core_initcall(pgd_cache_init);
+
+static inline pgd_t *_pgd_alloc(void)
+{
+       /*
+        * If no SHARED_KERNEL_PMD, PAE kernel is running as a Xen domain.
+        * We allocate one page for pgd.
+        */
+       if (!SHARED_KERNEL_PMD)
+               return (pgd_t *)__get_free_page(PGALLOC_GFP);
+
+       /*
+        * Now PAE kernel is not running as a Xen domain. We can allocate
+        * a 32-byte slab for pgd to save memory space.
+        */
+       return kmem_cache_alloc(pgd_cache, PGALLOC_GFP);
+}
+
+static inline void _pgd_free(pgd_t *pgd)
+{
+       if (!SHARED_KERNEL_PMD)
+               free_page((unsigned long)pgd);
+       else
+               kmem_cache_free(pgd_cache, pgd);
+}
+#else
+static inline pgd_t *_pgd_alloc(void)
+{
+       return (pgd_t *)__get_free_page(PGALLOC_GFP);
+}
+
+static inline void _pgd_free(pgd_t *pgd)
+{
+       free_page((unsigned long)pgd);
+}
+#endif /* CONFIG_X86_PAE */
+
 pgd_t *pgd_alloc(struct mm_struct *mm)
 {
        pgd_t *pgd;
        pmd_t *pmds[PREALLOCATED_PMDS];
 
-       pgd = (pgd_t *)__get_free_page(PGALLOC_GFP);
+       pgd = _pgd_alloc();
 
        if (pgd == NULL)
                goto out;
@@ -310,7 +385,7 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
 out_free_pmds:
        free_pmds(mm, pmds);
 out_free_pgd:
-       free_page((unsigned long)pgd);
+       _pgd_free(pgd);
 out:
        return NULL;
 }
@@ -320,7 +395,7 @@ void pgd_free(struct mm_struct *mm, pgd_t *pgd)
        pgd_mop_up_pmds(mm, pgd);
        pgd_dtor(pgd);
        paravirt_pgd_free(mm, pgd);
-       free_page((unsigned long)pgd);
+       _pgd_free(pgd);
 }
 
 /*