x86: 64-bit, add the new split_large_page() function

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 71 insertions, 24 deletions

diff --git a/arch/x86/mm/pageattr_64.c b/arch/x86/mm/pageattr_64.c
index 190d4d37bc2f..139795029fb6 100644
--- a/arch/x86/mm/pageattr_64.c
+++ b/arch/x86/mm/pageattr_64.c
@@ -45,34 +45,91 @@ pte_t *lookup_address(unsigned long address, int *level)
         return pte_offset_kernel(pmd, address);
 }
 
-static struct page *
-split_large_page(unsigned long address, pgprot_t ref_prot)
+static void __set_pmd_pte(pte_t *kpte, unsigned long address, pte_t pte)
 {
+        /* change init_mm */
+        set_pte_atomic(kpte, pte);
+#ifdef CONFIG_X86_32
+        if (SHARED_KERNEL_PMD)
+                return;
+        {
+                struct page *page;
+
+                for (page = pgd_list; page; page = (struct page *)page->index) {
+                        pgd_t *pgd;
+                        pud_t *pud;
+                        pmd_t *pmd;
+
+                        pgd = (pgd_t *)page_address(page) + pgd_index(address);
+                        pud = pud_offset(pgd, address);
+                        pmd = pmd_offset(pud, address);
+                        set_pte_atomic((pte_t *)pmd, pte);
+                }
+        }
+#endif
+}
+
+static int split_large_page(pte_t *kpte, unsigned long address)
+{
+        pgprot_t ref_prot = pte_pgprot(pte_clrhuge(*kpte));
+        gfp_t gfp_flags = GFP_KERNEL;
+        unsigned long flags;
         unsigned long addr;
+        pte_t *pbase, *tmp;
         struct page *base;
-        pte_t *pbase;
-        int i;
+        int i, level;
+
 
-        base = alloc_pages(GFP_KERNEL, 0);
+#ifdef CONFIG_DEBUG_PAGEALLOC
+        gfp_flags = GFP_ATOMIC;
+#endif
+        base = alloc_pages(gfp_flags, 0);
         if (!base)
-                return NULL;
+                return -ENOMEM;
+
+        spin_lock_irqsave(&pgd_lock, flags);
+        /*
+         * Check for races, another CPU might have split this page
+         * up for us already:
+         */
+        tmp = lookup_address(address, &level);
+        if (tmp != kpte) {
+                WARN_ON_ONCE(1);
+                goto out_unlock;
+        }
 
         address = __pa(address);
         addr = address & LARGE_PAGE_MASK;
         pbase = (pte_t *)page_address(base);
+#ifdef CONFIG_X86_32
+        paravirt_alloc_pt(&init_mm, page_to_pfn(base));
+#endif
+
         for (i = 0; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE)
-                pbase[i] = pfn_pte(addr >> PAGE_SHIFT, ref_prot);
+                set_pte(&pbase[i], pfn_pte(addr >> PAGE_SHIFT, ref_prot));
+
+        /*
+         * Install the new, split up pagetable:
+         */
+        __set_pmd_pte(kpte, address, mk_pte(base, ref_prot));
+        base = NULL;
+
+out_unlock:
+        spin_unlock_irqrestore(&pgd_lock, flags);
+
+        if (base)
+                __free_pages(base, 0);
 
-        return base;
+        return 0;
 }
 
 static int
 __change_page_attr(unsigned long address, struct page *page, pgprot_t prot)
 {
+        pgprot_t ref_prot2, oldprot;
         struct page *kpte_page;
+        int level, err = 0;
         pte_t *kpte;
-        pgprot_t ref_prot2, oldprot;
-        int level;
 
 repeat:
         kpte = lookup_address(address, &level);
@@ -88,22 +145,12 @@ repeat:
         if (level == 4) {
                 set_pte_atomic(kpte, mk_pte(page, prot));
         } else {
-                /*
-                 * split_large_page will take the reference for this
-                 * change_page_attr on the split page.
-                 */
-                struct page *split;
-
-                ref_prot2 = pte_pgprot(pte_clrhuge(*kpte));
-                split = split_large_page(address, ref_prot2);
-                if (!split)
-                        return -ENOMEM;
-                pgprot_val(ref_prot2) &= ~_PAGE_NX;
-                set_pte_atomic(kpte, mk_pte(split, ref_prot2));
-                goto repeat;
+                err = split_large_page(kpte, address);
+                if (!err)
+                        goto repeat;
         }
 
-        return 0;
+        return err;
 }
 
 /**