x86/pmap: count PTEs per PTP at initialization

This is required in order to properly release page table pages when removing
mappings from the kernel physical map.

2 files changed, 57 insertions, 0 deletions

diff --git a/arch/x86/machine/pmap.c b/arch/x86/machine/pmap.c
index 396edb4..3d53ef2 100644
--- a/arch/x86/machine/pmap.c
+++ b/arch/x86/machine/pmap.c
@@ -776,9 +776,54 @@ error_page:
 }
 #endif /* X86_PAE */
 
+static void __init
+pmap_setup_count_ptes(void)
+{
+    const struct pmap_pt_level *pt_level;
+    struct vm_page *page;
+    unsigned long va;
+    unsigned int level;
+    pmap_pte_t *pte;
+
+    va = 0;
+
+    /*
+     * Only count entries at lowest level. Accounting on upper PTPs is done
+     * when walking the recursive mapping.
+     */
+    do {
+#ifdef __LP64__
+        /* Handle long mode canonical form */
+        if (va == ((PMAP_VA_MASK >> 1) + 1))
+            va = ~(PMAP_VA_MASK >> 1);
+#endif /* __LP64__ */
+
+        for (level = PMAP_NR_LEVELS; level > 0; level--) {
+            pt_level = &pmap_pt_levels[level - 1];
+            pte = &pt_level->ptes[PMAP_PTEMAP_INDEX(va, pt_level->shift)];
+
+            if (*pte == 0) {
+                pte = NULL;
+                va = P2END(va, 1UL << pt_level->shift);
+                break;
+            }
+        }
+
+        if (pte == NULL)
+            continue;
+
+        page = vm_kmem_lookup_page(vm_page_trunc((unsigned long)pte));
+        assert(page != NULL);
+        page->pmap_page.nr_ptes++;
+        va += PAGE_SIZE;
+    } while (va != 0);
+}
+
 void __init
 pmap_setup(void)
 {
+    pmap_setup_count_ptes();
+
     kmem_cache_init(&pmap_cache, "pmap", sizeof(struct pmap),
                     0, NULL, NULL, NULL, 0);
 
diff --git a/arch/x86/machine/pmap.h b/arch/x86/machine/pmap.h
index 8a03e19..5d51480 100644
--- a/arch/x86/machine/pmap.h
+++ b/arch/x86/machine/pmap.h
@@ -128,6 +128,18 @@ struct pmap {
 extern struct pmap *kernel_pmap;
 
 /*
+ * Per physical page data specific to the pmap module.
+ *
+ * On this architecture, the number of page table entries is stored in page
+ * table page descriptors.
+ */
+struct pmap_page {
+    unsigned short nr_ptes;
+};
+
+#define PMAP_DEFINE_PAGE
+
+/*
  * Early initialization of the MMU.
  *
  * This function is called before paging is enabled by the boot module. It