[RFC PATCH 16/26] migration: Load confidential guest RAM using migration helper

[Dov Murik <dovmurik@linux.vnet.ibm.com>]

When loading encrypted RAM pages of a confidential guest, ask the
in-guest migration helper to decrypt the incoming page and place it
correctly in the guest memory at the appropriate address.  This way the
page's plaintext content remains inaccessible to the host.

Signed-off-by: Dov Murik <dovmurik@linux.vnet.ibm.com>
---
 migration/ram.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/migration/ram.c b/migration/ram.c
index 8e55ed49fd..82a1d13f5f 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3519,6 +3519,10 @@ void colo_release_ram_cache(void)
  */
 static int ram_load_setup(QEMUFile *f, void *opaque)
 {
+    if (confidential_guest()) {
+        cgs_mh_init();
+    }
+
     if (compress_threads_load_setup(f)) {
         return -1;
     }
@@ -3812,6 +3816,8 @@ void colo_flush_ram_cache(void)
 static int ram_load_precopy(QEMUFile *f)
 {
     int flags = 0, ret = 0, invalid_flags = 0, len = 0, i = 0;
+    ram_addr_t gpa;
+
     /* ADVISE is earlier, it shows the source has the postcopy capability on */
     bool postcopy_advised = postcopy_is_advised();
     if (!migrate_use_compression()) {
@@ -3848,7 +3854,8 @@ static int ram_load_precopy(QEMUFile *f)
         }
 
         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_GUEST_ENCRYPTED_PAGE)) {
             RAMBlock *block = ram_block_from_stream(f, flags);
 
             host = host_from_ram_block_offset(block, addr);
@@ -3977,6 +3984,16 @@ static int ram_load_precopy(QEMUFile *f)
                 break;
             }
             break;
+
+        case RAM_SAVE_FLAG_GUEST_ENCRYPTED_PAGE:
+            if (!kvm_physical_memory_addr_from_host(kvm_state, host, &gpa)) {
+                error_report("%s: failed to get gpa for host %p", __func__, host);
+                ret = -EINVAL;
+                break;
+            }
+            ret = cgs_mh_load_encrypted_page(f, gpa);
+            break;
+
         case RAM_SAVE_FLAG_EOS:
             /* normal exit */
             multifd_recv_sync_main();
-- 
2.20.1