x86/mm: Add support for changing the memory encryption attribute

Add support for changing the memory encryption attribute for one or more
memory pages. This will be useful when we have to change the AP trampoline
area to not be encrypted. Or when we need to change the SWIOTLB area to
not be encrypted in support of devices that can't support the encryption
mask range.

Signed-off-by: Tom Lendacky <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Reviewed-by: Borislav Petkov <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brijesh Singh <[email protected]>
Cc: Dave Young <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Konrad Rzeszutek Wilk <[email protected]>
Cc: Larry Woodman <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Matt Fleming <[email protected]>
Cc: Michael S. Tsirkin <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Radim Krčmář <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Toshimitsu Kani <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/924ae0d1f6d4c90c5a0e366c291b90a2d86aa79e.1500319216.git.thomas.lendacky@amd.com
Signed-off-by: Ingo Molnar <[email protected]>

2 files changed, 65 insertions, 0 deletions

diff --git a/arch/x86/include/asm/set_memory.h b/arch/x86/include/asm/set_memory.h
index eaec6c364e42..cd71273ec49d 100644
--- a/arch/x86/include/asm/set_memory.h
+++ b/arch/x86/include/asm/set_memory.h
@@ -11,6 +11,7 @@
  * Executability : eXeutable, NoteXecutable
  * Read/Write    : ReadOnly, ReadWrite
  * Presence      : NotPresent
+ * Encryption    : Encrypted, Decrypted
  *
  * Within a category, the attributes are mutually exclusive.
  *
@@ -42,6 +43,8 @@ int set_memory_wt(unsigned long addr, int numpages);
 int set_memory_wb(unsigned long addr, int numpages);
 int set_memory_np(unsigned long addr, int numpages);
 int set_memory_4k(unsigned long addr, int numpages);
+int set_memory_encrypted(unsigned long addr, int numpages);
+int set_memory_decrypted(unsigned long addr, int numpages);
 
 int set_memory_array_uc(unsigned long *addr, int addrinarray);
 int set_memory_array_wc(unsigned long *addr, int addrinarray);
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 7e2d6c0a64c4..9c8ea129ff5c 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1775,6 +1775,68 @@ int set_memory_4k(unsigned long addr, int numpages)
 					__pgprot(0), 1, 0, NULL);
 }
 
+static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
+{
+	struct cpa_data cpa;
+	unsigned long start;
+	int ret;
+
+	/* Nothing to do if the SME is not active */
+	if (!sme_active())
+		return 0;
+
+	/* Should not be working on unaligned addresses */
+	if (WARN_ONCE(addr & ~PAGE_MASK, "misaligned address: %#lx\n", addr))
+		addr &= PAGE_MASK;
+
+	start = addr;
+
+	memset(&cpa, 0, sizeof(cpa));
+	cpa.vaddr = &addr;
+	cpa.numpages = numpages;
+	cpa.mask_set = enc ? __pgprot(_PAGE_ENC) : __pgprot(0);
+	cpa.mask_clr = enc ? __pgprot(0) : __pgprot(_PAGE_ENC);
+	cpa.pgd = init_mm.pgd;
+
+	/* Must avoid aliasing mappings in the highmem code */
+	kmap_flush_unused();
+	vm_unmap_aliases();
+
+	/*
+	 * Before changing the encryption attribute, we need to flush caches.
+	 */
+	if (static_cpu_has(X86_FEATURE_CLFLUSH))
+		cpa_flush_range(start, numpages, 1);
+	else
+		cpa_flush_all(1);
+
+	ret = __change_page_attr_set_clr(&cpa, 1);
+
+	/*
+	 * After changing the encryption attribute, we need to flush TLBs
+	 * again in case any speculative TLB caching occurred (but no need
+	 * to flush caches again).  We could just use cpa_flush_all(), but
+	 * in case TLB flushing gets optimized in the cpa_flush_range()
+	 * path use the same logic as above.
+	 */
+	if (static_cpu_has(X86_FEATURE_CLFLUSH))
+		cpa_flush_range(start, numpages, 0);
+	else
+		cpa_flush_all(0);
+
+	return ret;
+}
+
+int set_memory_encrypted(unsigned long addr, int numpages)
+{
+	return __set_memory_enc_dec(addr, numpages, true);
+}
+
+int set_memory_decrypted(unsigned long addr, int numpages)
+{
+	return __set_memory_enc_dec(addr, numpages, false);
+}
+
 int set_pages_uc(struct page *page, int numpages)
 {
 	unsigned long addr = (unsigned long)page_address(page);