[RFC, PATCH 19/22] x86/mm: Implement free_encrypt_page()

[Kirill A. Shutemov]

As on allocation of encrypted page, we need to flush cache before
returning page to free pool. Failing to do this may lead to data
corruption.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 arch/x86/mm/mktme.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/x86/mm/mktme.c b/arch/x86/mm/mktme.c
index 1129ad25b22a..ef0eb1eb8d6e 100644
--- a/arch/x86/mm/mktme.c
+++ b/arch/x86/mm/mktme.c
@@ -45,6 +45,19 @@ void prep_encrypt_page(struct page *page, gfp_t gfp, unsigned int order)
 	WARN_ONCE(gfp & __GFP_ZERO, "__GFP_ZERO is useless for encrypted pages");
 }
 
+void free_encrypt_page(struct page *page, int keyid, unsigned int order)
+{
+	int i;
+	void *v;
+
+	for (i = 0; i < (1 << order); i++) {
+		v = kmap_atomic_keyid(page, keyid + i);
+		/* See comment in prep_encrypt_page() */
+		clflush_cache_range(v, PAGE_SIZE);
+		kunmap_atomic(v);
+	}
+}
+
 struct page *__alloc_zeroed_encrypted_user_highpage(gfp_t gfp,
 		struct vm_area_struct *vma, unsigned long vaddr)
 {
-- 
2.16.1