[PATCH, RFC 05/62] mm/page_alloc: Handle allocation for encrypted memory

["Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>]

For encrypted memory, we need to allocate pages for a specific
encryption KeyID.

There are two cases when we need to allocate a page for encryption:

 - Allocation for an encrypted VMA;

 - Allocation for migration of encrypted page;

The first case can be covered within alloc_page_vma(). We know KeyID
from the VMA.

The second case requires few new page allocation routines that would
allocate the page for a specific KeyID.

An encrypted page has to be cleared after KeyID set. This is handled
in prep_encrypted_page() that will be provided by arch-specific code.

Any custom allocator that dials with encrypted pages has to call
prep_encrypted_page() too. See compaction_alloc() for instance.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 include/linux/gfp.h     | 45 ++++++++++++++++++++++++++++++++-----
 include/linux/migrate.h | 14 +++++++++---
 mm/compaction.c         |  3 +++
 mm/mempolicy.c          | 27 ++++++++++++++++------
 mm/migrate.c            |  4 ++--
 mm/page_alloc.c         | 50 +++++++++++++++++++++++++++++++++++++++++
 6 files changed, 126 insertions(+), 17 deletions(-)

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index b101aa294157..1716dbe587c9 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -463,16 +463,43 @@ static inline void arch_free_page(struct page *page, int order) { }
 static inline void arch_alloc_page(struct page *page, int order) { }
 #endif
 
+#ifndef prep_encrypted_page
+static inline void prep_encrypted_page(struct page *page, int order,
+		int keyid, bool zero)
+{
+}
+#endif
+
+/*
+ * Encrypted page has to be cleared once keyid is set, not on allocation.
+ */
+static inline bool deferred_page_zero(int keyid, gfp_t *gfp_mask)
+{
+	if (keyid && (*gfp_mask & __GFP_ZERO)) {
+		*gfp_mask &= ~__GFP_ZERO;
+		return true;
+	}
+
+	return false;
+}
+
 struct page *
 __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid,
 							nodemask_t *nodemask);
 
+struct page *
+__alloc_pages_nodemask_keyid(gfp_t gfp_mask, unsigned int order,
+		int preferred_nid, nodemask_t *nodemask, int keyid);
+
 static inline struct page *
 __alloc_pages(gfp_t gfp_mask, unsigned int order, int preferred_nid)
 {
 	return __alloc_pages_nodemask(gfp_mask, order, preferred_nid, NULL);
 }
 
+struct page *__alloc_pages_node_keyid(int nid, int keyid,
+		gfp_t gfp_mask, unsigned int order);
+
 /*
  * Allocate pages, preferring the node given as nid. The node must be valid and
  * online. For more general interface, see alloc_pages_node().
@@ -500,6 +527,19 @@ static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask,
 	return __alloc_pages_node(nid, gfp_mask, order);
 }
 
+static inline struct page *alloc_pages_node_keyid(int nid, int keyid,
+		gfp_t gfp_mask, unsigned int order)
+{
+	if (nid = NUMA_NO_NODE)
+		nid = numa_mem_id();
+
+	return __alloc_pages_node_keyid(nid, keyid, gfp_mask, order);
+}
+
+extern struct page *alloc_pages_vma(gfp_t gfp_mask, int order,
+			struct vm_area_struct *vma, unsigned long addr,
+			int node, bool hugepage);
+
 #ifdef CONFIG_NUMA
 extern struct page *alloc_pages_current(gfp_t gfp_mask, unsigned order);
 
@@ -508,14 +548,9 @@ alloc_pages(gfp_t gfp_mask, unsigned int order)
 {
 	return alloc_pages_current(gfp_mask, order);
 }
-extern struct page *alloc_pages_vma(gfp_t gfp_mask, int order,
-			struct vm_area_struct *vma, unsigned long addr,
-			int node, bool hugepage);
 #else
 #define alloc_pages(gfp_mask, order) \
 		alloc_pages_node(numa_node_id(), gfp_mask, order)
-#define alloc_pages_vma(gfp_mask, order, vma, addr, node, false)\
-	alloc_pages(gfp_mask, order)
 #endif
 #define alloc_page(gfp_mask) alloc_pages(gfp_mask, 0)
 #define alloc_page_vma(gfp_mask, vma, addr)			\
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index e13d9bf2f9a5..a6e068762d08 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -38,9 +38,16 @@ static inline struct page *new_page_nodemask(struct page *page,
 	unsigned int order = 0;
 	struct page *new_page = NULL;
 
-	if (PageHuge(page))
+	if (PageHuge(page)) {
+		/*
+		 * HugeTLB doesn't support encryption. We shouldn't see
+		 * such pages.
+		 */
+		if (WARN_ON_ONCE(page_keyid(page)))
+			return NULL;
 		return alloc_huge_page_nodemask(page_hstate(compound_head(page)),
 				preferred_nid, nodemask);
+	}
 
 	if (PageTransHuge(page)) {
 		gfp_mask |= GFP_TRANSHUGE;
@@ -50,8 +57,9 @@ static inline struct page *new_page_nodemask(struct page *page,
 	if (PageHighMem(page) || (zone_idx(page_zone(page)) = ZONE_MOVABLE))
 		gfp_mask |= __GFP_HIGHMEM;
 
-	new_page = __alloc_pages_nodemask(gfp_mask, order,
-				preferred_nid, nodemask);
+	/* Allocate a page with the same KeyID as the source page */
+	new_page = __alloc_pages_nodemask_keyid(gfp_mask, order,
+				preferred_nid, nodemask, page_keyid(page));
 
 	if (new_page && PageTransHuge(new_page))
 		prep_transhuge_page(new_page);
diff --git a/mm/compaction.c b/mm/compaction.c
index 3319e0872d01..559b8bd6d245 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1557,6 +1557,9 @@ static struct page *compaction_alloc(struct page *migratepage,
 	list_del(&freepage->lru);
 	cc->nr_freepages--;
 
+	/* Prepare the page using the same KeyID as the source page */
+	if (freepage)
+		prep_encrypted_page(freepage, 0, page_keyid(migratepage), false);
 	return freepage;
 }
 
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 14b18449c623..5cad39fb7b35 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -961,22 +961,29 @@ static void migrate_page_add(struct page *page, struct list_head *pagelist,
 /* page allocation callback for NUMA node migration */
 struct page *alloc_new_node_page(struct page *page, unsigned long node)
 {
-	if (PageHuge(page))
+	if (PageHuge(page)) {
+		/*
+		 * HugeTLB doesn't support encryption. We shouldn't see
+		 * such pages.
+		 */
+		if (WARN_ON_ONCE(page_keyid(page)))
+			return NULL;
 		return alloc_huge_page_node(page_hstate(compound_head(page)),
 					node);
-	else if (PageTransHuge(page)) {
+	} else if (PageTransHuge(page)) {
 		struct page *thp;
 
-		thp = alloc_pages_node(node,
+		thp = alloc_pages_node_keyid(node, page_keyid(page),
 			(GFP_TRANSHUGE | __GFP_THISNODE),
 			HPAGE_PMD_ORDER);
 		if (!thp)
 			return NULL;
 		prep_transhuge_page(thp);
 		return thp;
-	} else
-		return __alloc_pages_node(node, GFP_HIGHUSER_MOVABLE |
-						    __GFP_THISNODE, 0);
+	} else {
+		return __alloc_pages_node_keyid(node, page_keyid(page),
+				GFP_HIGHUSER_MOVABLE | __GFP_THISNODE, 0);
+	}
 }
 
 /*
@@ -2053,9 +2060,13 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
 {
 	struct mempolicy *pol;
 	struct page *page;
-	int preferred_nid;
+	bool deferred_zero;
+	int keyid, preferred_nid;
 	nodemask_t *nmask;
 
+	keyid = vma_keyid(vma);
+	deferred_zero = deferred_page_zero(keyid, &gfp);
+
 	pol = get_vma_policy(vma, addr);
 
 	if (pol->mode = MPOL_INTERLEAVE) {
@@ -2097,6 +2108,8 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
 	page = __alloc_pages_nodemask(gfp, order, preferred_nid, nmask);
 	mpol_cond_put(pol);
 out:
+	if (page)
+		prep_encrypted_page(page, order, keyid, deferred_zero);
 	return page;
 }
 
diff --git a/mm/migrate.c b/mm/migrate.c
index 663a5449367a..04b36a56865d 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1880,7 +1880,7 @@ static struct page *alloc_misplaced_dst_page(struct page *page,
 	int nid = (int) data;
 	struct page *newpage;
 
-	newpage = __alloc_pages_node(nid,
+	newpage = __alloc_pages_node_keyid(nid, page_keyid(page),
 					 (GFP_HIGHUSER_MOVABLE |
 					  __GFP_THISNODE | __GFP_NOMEMALLOC |
 					  __GFP_NORETRY | __GFP_NOWARN) &
@@ -2006,7 +2006,7 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
 	int page_lru = page_is_file_cache(page);
 	unsigned long start = address & HPAGE_PMD_MASK;
 
-	new_page = alloc_pages_node(node,
+	new_page = alloc_pages_node_keyid(node, page_keyid(page),
 		(GFP_TRANSHUGE_LIGHT | __GFP_THISNODE),
 		HPAGE_PMD_ORDER);
 	if (!new_page)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c02cff1ed56e..ab1d8661aa87 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3930,6 +3930,41 @@ should_compact_retry(struct alloc_context *ac, unsigned int order, int alloc_fla
 }
 #endif /* CONFIG_COMPACTION */
 
+#ifndef CONFIG_NUMA
+struct page *alloc_pages_vma(gfp_t gfp_mask, int order,
+		struct vm_area_struct *vma, unsigned long addr,
+		int node, bool hugepage)
+{
+	struct page *page;
+	bool deferred_zero;
+	int keyid = vma_keyid(vma);
+
+	deferred_zero = deferred_page_zero(keyid, &gfp_mask);
+	page = alloc_pages(gfp_mask, order);
+	if (page)
+		prep_encrypted_page(page, order, keyid, deferred_zero);
+
+	return page;
+}
+#endif
+
+struct page * __alloc_pages_node_keyid(int nid, int keyid,
+		gfp_t gfp_mask, unsigned int order)
+{
+	struct page *page;
+	bool deferred_zero;
+
+	VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES);
+	VM_WARN_ON(!node_online(nid));
+
+	deferred_zero = deferred_page_zero(keyid, &gfp_mask);
+	page = __alloc_pages(gfp_mask, order, nid);
+	if (page)
+		prep_encrypted_page(page, order, keyid, deferred_zero);
+
+	return page;
+}
+
 #ifdef CONFIG_LOCKDEP
 static struct lockdep_map __fs_reclaim_map  	STATIC_LOCKDEP_MAP_INIT("fs_reclaim", &__fs_reclaim_map);
@@ -4645,6 +4680,21 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid,
 }
 EXPORT_SYMBOL(__alloc_pages_nodemask);
 
+struct page *
+__alloc_pages_nodemask_keyid(gfp_t gfp_mask, unsigned int order,
+		int preferred_nid, nodemask_t *nodemask, int keyid)
+{
+	struct page *page;
+	bool deferred_zero;
+
+	deferred_zero = deferred_page_zero(keyid, &gfp_mask);
+	page = __alloc_pages_nodemask(gfp_mask, order, preferred_nid, nodemask);
+	if (page)
+		prep_encrypted_page(page, order, keyid, deferred_zero);
+	return page;
+}
+EXPORT_SYMBOL(__alloc_pages_nodemask_keyid);
+
 /*
  * Common helper functions. Never use with __GFP_HIGHMEM because the returned
  * address cannot represent highmem pages. Use alloc_pages and then kmap if
-- 
2.20.1