[Qemu-devel] [PATCH v2 03/13] migration/ram: add support to send encrypted pages

["Singh, Brijesh" <brijesh.singh@amd.com>]

When memory encryption is enabled, the guest memory will be encrypted with
the guest specific key. The patch introduces RAM_SAVE_FLAG_ENCRYPTED_PAGE
flag to distinguish the encrypted data from plaintext. Encrypted pages
may need special handling. The kvm_memcrypt_save_outgoing_page() is used
by the sender to write the encrypted pages onto the socket, similarly the
kvm_memcrypt_load_incoming_page() is used by the target to read the
encrypted pages from the socket and load into the guest memory.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 migration/ram.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 53 insertions(+), 1 deletion(-)

diff --git a/migration/ram.c b/migration/ram.c
index 908517fc2b..3c8977d508 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -57,6 +57,7 @@
 #include "qemu/uuid.h"
 #include "savevm.h"
 #include "qemu/iov.h"
+#include "sysemu/kvm.h"
 
 /***********************************************************/
 /* ram save/restore */
@@ -76,6 +77,7 @@
 #define RAM_SAVE_FLAG_XBZRLE   0x40
 /* 0x80 is reserved in migration.h start with 0x100 next */
 #define RAM_SAVE_FLAG_COMPRESS_PAGE    0x100
+#define RAM_SAVE_FLAG_ENCRYPTED_PAGE   0x200
 
 static inline bool is_zero_range(uint8_t *p, uint64_t size)
 {
@@ -460,6 +462,9 @@ static QemuCond decomp_done_cond;
 static bool do_compress_ram_page(QEMUFile *f, z_stream *stream, RAMBlock *block,
                                  ram_addr_t offset, uint8_t *source_buf);
 
+static int ram_save_encrypted_page(RAMState *rs, PageSearchStatus *pss,
+                                   bool last_stage);
+
 static void *do_data_compress(void *opaque)
 {
     CompressParam *param = opaque;
@@ -2006,6 +2011,36 @@ static int ram_save_multifd_page(RAMState *rs, RAMBlock *block,
     return 1;
 }
 
+/**
+ * ram_save_encrypted_page - send the given encrypted page to the stream
+ */
+static int ram_save_encrypted_page(RAMState *rs, PageSearchStatus *pss,
+                                   bool last_stage)
+{
+    int ret;
+    uint8_t *p;
+    RAMBlock *block = pss->block;
+    ram_addr_t offset = pss->page << TARGET_PAGE_BITS;
+    uint64_t bytes_xmit;
+
+    p = block->host + offset;
+
+    ram_counters.transferred +=
+        save_page_header(rs, rs->f, block,
+                    offset | RAM_SAVE_FLAG_ENCRYPTED_PAGE);
+
+    ret = kvm_memcrypt_save_outgoing_page(rs->f, p,
+                        TARGET_PAGE_SIZE, &bytes_xmit);
+    if (ret) {
+        return -1;
+    }
+
+    ram_counters.transferred += bytes_xmit;
+    ram_counters.normal++;
+
+    return 1;
+}
+
 static bool do_compress_ram_page(QEMUFile *f, z_stream *stream, RAMBlock *block,
                                  ram_addr_t offset, uint8_t *source_buf)
 {
@@ -2450,6 +2485,16 @@ static int ram_save_target_page(RAMState *rs, PageSearchStatus *pss,
         return res;
     }
 
+    /*
+     * If memory encryption is enabled then use memory encryption APIs
+     * to write the outgoing buffer to the wire. The encryption APIs
+     * will take care of accessing the guest memory and re-encrypt it
+     * for the transport purposes.
+     */
+     if (kvm_memcrypt_enabled()) {
+        return ram_save_encrypted_page(rs, pss, last_stage);
+     }
+
     if (save_compress_page(rs, block, offset)) {
         return 1;
     }
@@ -4271,7 +4316,8 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
         }
 
         if (flags & (RAM_SAVE_FLAG_ZERO | RAM_SAVE_FLAG_PAGE |
-                     RAM_SAVE_FLAG_COMPRESS_PAGE | RAM_SAVE_FLAG_XBZRLE)) {
+                     RAM_SAVE_FLAG_COMPRESS_PAGE | RAM_SAVE_FLAG_XBZRLE |
+                     RAM_SAVE_FLAG_ENCRYPTED_PAGE)) {
             RAMBlock *block = ram_block_from_stream(f, flags);
 
             /*
@@ -4391,6 +4437,12 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
                 break;
             }
             break;
+        case RAM_SAVE_FLAG_ENCRYPTED_PAGE:
+            if (kvm_memcrypt_load_incoming_page(f, host)) {
+                    error_report("Failed to encrypted incoming data");
+                    ret = -EINVAL;
+            }
+            break;
         case RAM_SAVE_FLAG_EOS:
             /* normal exit */
             multifd_recv_sync_main();
-- 
2.17.1