[RFC PATCH v4 16/28] x86: Add support for changing memory encryption attribute

Tom Lendacky
2017-02-16T15:45:51Z

Add support for changing the memory encryption attribute for one or more
memory pages.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
arch/x86/include/asm/cacheflush.h | 3 ++
arch/x86/mm/pageattr.c | 66 +++++++++++++++++++++++++++++++++++++
2 files changed, 69 insertions(+)

diff --git a/arch/x86/include/asm/cacheflush.h b/arch/x86/include/asm/cacheflush.h
index 872877d..33ae60a 100644
--- a/arch/x86/include/asm/cacheflush.h
+++ b/arch/x86/include/asm/cacheflush.h
@@ -12,6 +12,7 @@
* Executability : eXeutable, NoteXecutable
* Read/Write : ReadOnly, ReadWrite
* Presence : NotPresent
+ * Encryption : Encrypted, Decrypted
*
* Within a category, the attributes are mutually exclusive.
*
@@ -47,6 +48,8 @@
int set_memory_rw(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 91c5c63..9710f5c 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1742,6 +1742,72 @@ 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 _PAGE_ENC attribute is zero */
+ if (_PAGE_ENC == 0)
+ return 0;
+
+ /* Save original start address since it will be modified */
+ 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;
+
+ /* Should not be working on unaligned addresses */
+ if (WARN_ONCE(*cpa.vaddr & ~PAGE_MASK,
+ "misaligned address: %#lx\n", *cpa.vaddr))
+ *cpa.vaddr &= PAGE_MASK;
+
+ /* 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);
+}
+EXPORT_SYMBOL(set_memory_encrypted);
+
+int set_memory_decrypted(unsigned long addr, int numpages)
+{
+ return __set_memory_enc_dec(addr, numpages, false);
+}
+EXPORT_SYMBOL(set_memory_decrypted);
+
int set_pages_uc(struct page *page, int numpages)
{
unsigned long addr = (unsigned long)page_address(page);