[RFC v2 05/13] x86/mm: Set KeyIDs in encrypted VMAs

[Alison Schofield]

MKTME architecture requires the KeyID to be placed in PTE bits 51:46.
To create an encrypted VMA, place the KeyID in the upper bits of
vm_page_prot that matches the position of those PTE bits.

When the VMA is assigned a KeyID it is always considered a KeyID
change. The VMA is either going from not encrypted to encrypted,
or from encrypted with any KeyID to encrypted with any other KeyID.
To make the change safely, remove the user pages held by the VMA
and unlink the VMA's anonymous chain.

Change-Id: I676056525c49c8803898315a10b196ef5a5c5415
Signed-off-by: Alison Schofield <alison.schofield at intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov at linux.intel.com>
---
 arch/x86/include/asm/mktme.h |  4 ++++
 arch/x86/mm/mktme.c          | 26 ++++++++++++++++++++++++++
 include/linux/mm.h           |  6 ++++++
 3 files changed, 36 insertions(+)

diff --git a/arch/x86/include/asm/mktme.h b/arch/x86/include/asm/mktme.h
index dbb49909d665..de3e529f3ab0 100644
--- a/arch/x86/include/asm/mktme.h
+++ b/arch/x86/include/asm/mktme.h
@@ -24,6 +24,10 @@ extern int mktme_map_keyid_from_key(void *key);
 extern void *mktme_map_key_from_keyid(int keyid);
 extern int mktme_map_get_free_keyid(void);
 
+/* Set the encryption keyid bits in a VMA */
+extern void mprotect_set_encrypt(struct vm_area_struct *vma, int newkeyid,
+				unsigned long start, unsigned long end);
+
 DECLARE_STATIC_KEY_FALSE(mktme_enabled_key);
 static inline bool mktme_enabled(void)
 {
diff --git a/arch/x86/mm/mktme.c b/arch/x86/mm/mktme.c
index 34224d4e3f45..e3fdf7b48173 100644
--- a/arch/x86/mm/mktme.c
+++ b/arch/x86/mm/mktme.c
@@ -1,5 +1,6 @@
 #include <linux/mm.h>
 #include <linux/highmem.h>
+#include <linux/rmap.h>
 #include <asm/mktme.h>
 #include <asm/set_memory.h>
 
@@ -131,6 +132,31 @@ int mktme_map_get_free_keyid(void)
 	return 0;
 }
 
+/* Set the encryption keyid bits in a VMA */
+void mprotect_set_encrypt(struct vm_area_struct *vma, int newkeyid,
+			  unsigned long start, unsigned long end)
+{
+	int oldkeyid = vma_keyid(vma);
+	pgprotval_t newprot;
+
+	/* Unmap pages with old KeyID if there's any. */
+	zap_page_range(vma, start, end - start);
+
+	if (oldkeyid == newkeyid)
+		return;
+
+	newprot = pgprot_val(vma->vm_page_prot);
+	newprot &= ~mktme_keyid_mask;
+	newprot |= (unsigned long)newkeyid << mktme_keyid_shift;
+	vma->vm_page_prot = __pgprot(newprot);
+
+	/*
+	 * The VMA doesn't have any inherited pages.
+	 * Start anon VMA tree from scratch.
+	 */
+	unlink_anon_vmas(vma);
+}
+
 /* Prepare page to be used for encryption. Called from page allocator. */
 void __prep_encrypted_page(struct page *page, int order, int keyid, bool zero)
 {
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1309761bb6d0..e2d87e92ca74 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2806,5 +2806,11 @@ void __init setup_nr_node_ids(void);
 static inline void setup_nr_node_ids(void) {}
 #endif
 
+#ifndef CONFIG_X86_INTEL_MKTME
+static inline void mprotect_set_encrypt(struct vm_area_struct *vma,
+					int newkeyid,
+					unsigned long start,
+					unsigned long end) {}
+#endif /* CONFIG_X86_INTEL_MKTME */
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MM_H */
-- 
2.14.1