x86/mm/pageattr: Add a PMD pagetable populating function

Handle PMD-level mappings the same as PUD ones.
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

arch/x86/mm/pageattr.c

@@ -666,6 +666,16 @@ static int split_large_page(pte_t *kpte, unsigned long address)
 	return 0;
 }
 
+static int alloc_pte_page(pmd_t *pmd)
+{
+	pte_t *pte = (pte_t *)get_zeroed_page(GFP_KERNEL | __GFP_NOTRACK);
+	if (!pte)
+		return -1;
+
+	set_pmd(pmd, __pmd(__pa(pte) | _KERNPG_TABLE));
+	return 0;
+}
+
 static int alloc_pmd_page(pud_t *pud)
 {
 	pmd_t *pmd = (pmd_t *)get_zeroed_page(GFP_KERNEL | __GFP_NOTRACK);
@@ -676,7 +686,77 @@ static int alloc_pmd_page(pud_t *pud)
 	return 0;
 }
 
-#define populate_pmd(cpa, start, end, pages, pud, pgprot)	(-1)
+#define populate_pte(cpa, start, end, pages, pmd, pgprot)	do {} while (0)
+
+static int populate_pmd(struct cpa_data *cpa,
+			unsigned long start, unsigned long end,
+			unsigned num_pages, pud_t *pud, pgprot_t pgprot)
+{
+	unsigned int cur_pages = 0;
+	pmd_t *pmd;
+
+	/*
+	 * Not on a 2M boundary?
+	 */
+	if (start & (PMD_SIZE - 1)) {
+		unsigned long pre_end = start + (num_pages << PAGE_SHIFT);
+		unsigned long next_page = (start + PMD_SIZE) & PMD_MASK;
+
+		pre_end   = min_t(unsigned long, pre_end, next_page);
+		cur_pages = (pre_end - start) >> PAGE_SHIFT;
+		cur_pages = min_t(unsigned int, num_pages, cur_pages);
+
+		/*
+		 * Need a PTE page?
+		 */
+		pmd = pmd_offset(pud, start);
+		if (pmd_none(*pmd))
+			if (alloc_pte_page(pmd))
+				return -1;
+
+		populate_pte(cpa, start, pre_end, cur_pages, pmd, pgprot);
+
+		start = pre_end;
+	}
+
+	/*
+	 * We mapped them all?
+	 */
+	if (num_pages == cur_pages)
+		return cur_pages;
+
+	while (end - start >= PMD_SIZE) {
+
+		/*
+		 * We cannot use a 1G page so allocate a PMD page if needed.
+		 */
+		if (pud_none(*pud))
+			if (alloc_pmd_page(pud))
+				return -1;
+
+		pmd = pmd_offset(pud, start);
+
+		set_pmd(pmd, __pmd(cpa->pfn | _PAGE_PSE | massage_pgprot(pgprot)));
+
+		start	  += PMD_SIZE;
+		cpa->pfn  += PMD_SIZE;
+		cur_pages += PMD_SIZE >> PAGE_SHIFT;
+	}
+
+	/*
+	 * Map trailing 4K pages.
+	 */
+	if (start < end) {
+		pmd = pmd_offset(pud, start);
+		if (pmd_none(*pmd))
+			if (alloc_pte_page(pmd))
+				return -1;
+
+		populate_pte(cpa, start, end, num_pages - cur_pages,
+			     pmd, pgprot);
+	}
+	return num_pages;
+}
 
 static int populate_pud(struct cpa_data *cpa, unsigned long start, pgd_t *pgd,
 			pgprot_t pgprot)