1 files changed, 93 insertions, 1 deletions

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 1cbdbbc35b47..db8ace29514f 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -666,7 +666,99 @@ static int split_large_page(pte_t *kpte, unsigned long address)
         return 0;
 }
 
-#define unmap_pmd_range(pud, start, pre_end)            do {} while (0)
+static bool try_to_free_pte_page(pte_t *pte)
+{
+        int i;
+
+        for (i = 0; i < PTRS_PER_PTE; i++)
+                if (!pte_none(pte[i]))
+                        return false;
+
+        free_page((unsigned long)pte);
+        return true;
+}
+
+static bool try_to_free_pmd_page(pmd_t *pmd)
+{
+        int i;
+
+        for (i = 0; i < PTRS_PER_PMD; i++)
+                if (!pmd_none(pmd[i]))
+                        return false;
+
+        free_page((unsigned long)pmd);
+        return true;
+}
+
+static bool unmap_pte_range(pmd_t *pmd, unsigned long start, unsigned long end)
+{
+        pte_t *pte = pte_offset_kernel(pmd, start);
+
+        while (start < end) {
+                set_pte(pte, __pte(0));
+
+                start += PAGE_SIZE;
+                pte++;
+        }
+
+        if (try_to_free_pte_page((pte_t *)pmd_page_vaddr(*pmd))) {
+                pmd_clear(pmd);
+                return true;
+        }
+        return false;
+}
+
+static void __unmap_pmd_range(pud_t *pud, pmd_t *pmd,
+                              unsigned long start, unsigned long end)
+{
+        if (unmap_pte_range(pmd, start, end))
+                if (try_to_free_pmd_page((pmd_t *)pud_page_vaddr(*pud)))
+                        pud_clear(pud);
+}
+
+static void unmap_pmd_range(pud_t *pud, unsigned long start, unsigned long end)
+{
+        pmd_t *pmd = pmd_offset(pud, start);
+
+        /*
+         * Not on a 2MB page boundary?
+         */
+        if (start & (PMD_SIZE - 1)) {
+                unsigned long next_page = (start + PMD_SIZE) & PMD_MASK;
+                unsigned long pre_end = min_t(unsigned long, end, next_page);
+
+                __unmap_pmd_range(pud, pmd, start, pre_end);
+
+                start = pre_end;
+                pmd++;
+        }
+
+        /*
+         * Try to unmap in 2M chunks.
+         */
+        while (end - start >= PMD_SIZE) {
+                if (pmd_large(*pmd))
+                        pmd_clear(pmd);
+                else
+                        __unmap_pmd_range(pud, pmd, start, start + PMD_SIZE);
+
+                start += PMD_SIZE;
+                pmd++;
+        }
+
+        /*
+         * 4K leftovers?
+         */
+        if (start < end)
+                return __unmap_pmd_range(pud, pmd, start, end);
+
+        /*
+         * Try again to free the PMD page if haven't succeeded above.
+         */
+        if (!pud_none(*pud))
+                if (try_to_free_pmd_page((pmd_t *)pud_page_vaddr(*pud)))
+                        pud_clear(pud);
+}
 
 static void unmap_pud_range(pgd_t *pgd, unsigned long start, unsigned long end)
 {