sev/i386: register the guest memory range which may contain encrypted…

… data

When SEV is enabled, the hardware encryption engine uses a tweak such
that the two identical plaintext at different location will have a
different ciphertexts. So swapping or moving a ciphertexts of two guest
pages will not result in plaintexts being swapped. Hence relocating
a physical backing pages of the SEV guest will require some additional
steps in KVM driver. The KVM_MEMORY_ENCRYPT_{UN,}REG_REGION ioctl can be
used to register/unregister the guest memory region which may contain the
encrypted data. KVM driver will internally handle the relocating physical
backing pages of registered memory regions.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

target/i386/sev.c

@@ -105,6 +105,46 @@ fw_error_to_str(int code)
     return sev_fw_errlist[code];
 }
 
+static void
+sev_ram_block_added(RAMBlockNotifier *n, void *host, size_t size)
+{
+    int r;
+    struct kvm_enc_region range;
+
+    range.addr = (__u64)(unsigned long)host;
+    range.size = size;
+
+    trace_kvm_memcrypt_register_region(host, size);
+    r = kvm_vm_ioctl(kvm_state, KVM_MEMORY_ENCRYPT_REG_REGION, &range);
+    if (r) {
+        error_report("%s: failed to register region (%p+%#zx) error '%s'",
+                     __func__, host, size, strerror(errno));
+        exit(1);
+    }
+}
+
+static void
+sev_ram_block_removed(RAMBlockNotifier *n, void *host, size_t size)
+{
+    int r;
+    struct kvm_enc_region range;
+
+    range.addr = (__u64)(unsigned long)host;
+    range.size = size;
+
+    trace_kvm_memcrypt_unregister_region(host, size);
+    r = kvm_vm_ioctl(kvm_state, KVM_MEMORY_ENCRYPT_UNREG_REGION, &range);
+    if (r) {
+        error_report("%s: failed to unregister region (%p+%#zx)",
+                     __func__, host, size);
+    }
+}
+
+static struct RAMBlockNotifier sev_ram_notifier = {
+    .ram_block_added = sev_ram_block_added,
+    .ram_block_removed = sev_ram_block_removed,
+};
+
 static void
 qsev_guest_finalize(Object *obj)
 {
@@ -436,6 +476,8 @@ sev_guest_init(const char *id)
         goto err;
     }
 
+    ram_block_notifier_add(&sev_ram_notifier);
+
     return s;
 err:
     g_free(sev_state);

target/i386/trace-events

@@ -8,3 +8,5 @@ kvm_x86_update_msi_routes(int num) "Updated %d MSI routes"
 
 # target/i386/sev.c
 kvm_sev_init(void) ""
+kvm_memcrypt_register_region(void *addr, size_t len) "addr %p len 0x%zu"
+kvm_memcrypt_unregister_region(void *addr, size_t len) "addr %p len 0x%zu"