[Qemu-devel] [PATCH v3 13/14] migration/ram: add support to send encrypted pages

[Singh, Brijesh]

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 <address@hidden>
---
 migration/ram.c | 131 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 130 insertions(+), 1 deletion(-)

diff --git a/migration/ram.c b/migration/ram.c
index 57c707525b..100a5a10cd 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -59,6 +59,9 @@
 #include "qemu/iov.h"
 #include "hw/boards.h"
 
+/* Defines RAM_SAVE_ENCRYPTED_PAGE and  RAM_SAVE_ENCRYPTED_BITMAP */
+#include "sysemu/sev.h"
+
 /***********************************************************/
 /* ram save/restore */
 
@@ -77,6 +80,7 @@
 #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_DATA   0x200
 
 static inline bool is_zero_range(uint8_t *p, uint64_t size)
 {
@@ -460,6 +464,9 @@ 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)
 {
@@ -2039,6 +2046,73 @@ static int save_normal_page(RAMState *rs, RAMBlock 
*block, ram_addr_t offset,
     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;
+    MachineState *ms = MACHINE(qdev_get_machine());
+    MachineClass *mc = MACHINE_GET_CLASS(ms);
+    struct MachineMemoryEncryptionOps *ops = mc->memory_encryption_ops;
+
+    p = block->host + offset;
+
+    ram_counters.transferred +=
+        save_page_header(rs, rs->f, block,
+                    offset | RAM_SAVE_FLAG_ENCRYPTED_DATA);
+
+    qemu_put_be32(rs->f, RAM_SAVE_ENCRYPTED_PAGE);
+    ret = ops->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;
+}
+
+/**
+ * ram_save_encrypted_bitmap: send the encrypted page state bitmap
+ */
+static int ram_save_encrypted_bitmap(RAMState *rs, QEMUFile *f)
+{
+    MachineState *ms = MACHINE(qdev_get_machine());
+    MachineClass *mc = MACHINE_GET_CLASS(ms);
+    struct MachineMemoryEncryptionOps *ops = mc->memory_encryption_ops;
+
+    save_page_header(rs, rs->f, rs->last_seen_block,
+                     RAM_SAVE_FLAG_ENCRYPTED_DATA);
+    qemu_put_be32(rs->f, RAM_SAVE_ENCRYPTED_BITMAP);
+    return ops->save_outgoing_bitmap(rs->f);
+}
+
+static int load_encrypted_data(QEMUFile *f, uint8_t *ptr)
+{
+    MachineState *ms = MACHINE(qdev_get_machine());
+    MachineClass *mc = MACHINE_GET_CLASS(ms);
+    struct MachineMemoryEncryptionOps *ops = mc->memory_encryption_ops;
+    int flag;
+
+    flag = qemu_get_be32(f);
+
+    if (flag == RAM_SAVE_ENCRYPTED_PAGE) {
+        return ops->load_incoming_page(f, ptr);
+    } else if (flag == RAM_SAVE_ENCRYPTED_BITMAP) {
+        return ops->load_incoming_bitmap(f);
+    } else {
+        error_report("unknown encrypted flag %x", flag);
+        return 1;
+    }
+}
+
 /**
  * ram_save_page: send the given page to the stream
  *
@@ -2528,6 +2602,22 @@ static bool save_compress_page(RAMState *rs, RAMBlock 
*block, ram_addr_t offset)
     return false;
 }
 
+/**
+ * encrypted_test_bitmap: check if the page is encrypted
+ *
+ * Returns a bool indicating whether the page is encrypted.
+ */
+static bool encrypted_test_bitmap(RAMState *rs, RAMBlock *block,
+                                  unsigned long page)
+{
+    /* ROM devices contains the unencrypted data */
+    if (memory_region_is_rom(block->mr)) {
+        return false;
+    }
+
+    return test_bit(page, block->encbmap);
+}
+
 /**
  * ram_save_target_page: save one target page
  *
@@ -2548,6 +2638,17 @@ 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 (memcrypt_enabled() &&
+        encrypted_test_bitmap(rs, pss->block, pss->page)) {
+        return ram_save_encrypted_page(rs, pss, last_stage);
+    }
+
     if (save_compress_page(rs, block, offset)) {
         return 1;
     }
@@ -3445,6 +3546,16 @@ void qemu_guest_free_page_hint(void *addr, size_t len)
     }
 }
 
+static int ram_encrypted_save_setup(void)
+{
+    MachineState *ms = MACHINE(qdev_get_machine());
+    MachineClass *mc = MACHINE_GET_CLASS(ms);
+    MigrationParameters *p = &migrate_get_current()->parameters;
+    struct MachineMemoryEncryptionOps *ops = mc->memory_encryption_ops;
+
+    return ops->save_setup(p->sev_pdh, p->sev_plat_cert, p->sev_amd_cert);
+}
+
 /*
  * Each of ram_save_setup, ram_save_iterate and ram_save_complete has
  * long-running RCU critical section.  When rcu-reclaims in the code
@@ -3480,6 +3591,12 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
 
     rcu_read_lock();
 
+    if (memcrypt_enabled()) {
+        if (ram_encrypted_save_setup()) {
+            return -1;
+        }
+    }
+
     qemu_put_be64(f, ram_bytes_total_common(true) | RAM_SAVE_FLAG_MEM_SIZE);
 
     RAMBLOCK_FOREACH_MIGRATABLE(block) {
@@ -3644,6 +3761,11 @@ static int ram_save_complete(QEMUFile *f, void *opaque)
     flush_compressed_data(rs);
     ram_control_after_iterate(f, RAM_CONTROL_FINISH);
 
+    /* send the page encryption state bitmap */
+    if (memcrypt_enabled()) {
+        ret = ram_save_encrypted_bitmap(rs, f);
+    }
+
     rcu_read_unlock();
 
     multifd_send_sync_main();
@@ -4391,7 +4513,8 @@ 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_DATA)) {
             RAMBlock *block = ram_block_from_stream(f, flags);
 
             /*
@@ -4505,6 +4628,12 @@ static int ram_load(QEMUFile *f, void *opaque, int 
version_id)
                 break;
             }
             break;
+        case RAM_SAVE_FLAG_ENCRYPTED_DATA:
+            if (load_encrypted_data(f, host)) {
+                    error_report("Failed to load encrypted data");
+                    ret = -EINVAL;
+            }
+            break;
         case RAM_SAVE_FLAG_EOS:
             /* normal exit */
             multifd_recv_sync_main();
-- 
2.17.1