tools: VM generation ID save/restore and migrate.

Add code to track the address of the VM generation ID buffer across a
save/restore or migrate, and increment it as necessary.
The address of the buffer is written into xenstore by hvmloader at
boot time. It must be read from xenstore by the caller of
xc_domain_save() and then written back again by the caller of
xc_domain_restore().

Note that the changes to xc_save.c and xc_restore.c are merely
sufficient for them to build.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Committed-by: Ian Jackson <ian.jackson.citrix.com>

1 files changed, 31 insertions, 4 deletions

diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index c898d89773..a4725fea32 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -106,6 +106,7 @@ int libxl__build_pre(libxl__gc *gc, uint32_t domid,
 
     state->store_port = xc_evtchn_alloc_unbound(ctx->xch, domid, 0);
     state->console_port = xc_evtchn_alloc_unbound(ctx->xch, domid, 0);
+    state->vm_generationid_addr = 0;
     return 0;
 }
 
@@ -117,7 +118,7 @@ int libxl__build_post(libxl__gc *gc, uint32_t domid,
     libxl_ctx *ctx = libxl__gc_owner(gc);
     char *dom_path, *vm_path;
     xs_transaction_t t;
-    char **ents;
+    char **ents, **hvm_ents;
     int i;
 
     libxl_cpuid_apply_policy(ctx, domid);
@@ -143,6 +144,13 @@ int libxl__build_post(libxl__gc *gc, uint32_t domid,
                             ? "offline" : "online";
     }
 
+    hvm_ents = NULL;
+    if (info->type == LIBXL_DOMAIN_TYPE_HVM) {
+        hvm_ents = libxl__calloc(gc, 3, sizeof(char *));
+        hvm_ents[0] = "hvmloader/generation-id-address";
+        hvm_ents[1] = libxl__sprintf(gc, "0x%lx", state->vm_generationid_addr);
+    }
+
     dom_path = libxl__xs_get_dompath(gc, domid);
     if (!dom_path) {
         return ERROR_FAIL;
@@ -153,6 +161,9 @@ retry_transaction:
     t = xs_transaction_start(ctx->xsh);
 
     libxl__xs_writev(gc, t, dom_path, ents);
+    if (info->type == LIBXL_DOMAIN_TYPE_HVM)
+        libxl__xs_writev(gc, t, dom_path, hvm_ents);
+
     libxl__xs_writev(gc, t, dom_path, local_ents);
     libxl__xs_writev(gc, t, vm_path, vms_ents);
 
@@ -356,16 +367,19 @@ int libxl__domain_restore_common(libxl__gc *gc, uint32_t domid,
     /* read signature */
     int rc;
     int hvm, pae, superpages;
+    int no_incr_generationid;
     switch (info->type) {
     case LIBXL_DOMAIN_TYPE_HVM:
         hvm = 1;
         superpages = 1;
         pae = info->u.hvm.pae;
+        no_incr_generationid = info->u.hvm.no_incr_generationid;
         break;
     case LIBXL_DOMAIN_TYPE_PV:
         hvm = 0;
         superpages = 0;
         pae = 1;
+        no_incr_generationid = 0;
         break;
     default:
         return ERROR_INVAL;
@@ -373,7 +387,8 @@ int libxl__domain_restore_common(libxl__gc *gc, uint32_t domid,
     rc = xc_domain_restore(ctx->xch, fd, domid,
                            state->store_port, &state->store_mfn,
                            state->console_port, &state->console_mfn,
-                           hvm, pae, superpages);
+                           hvm, pae, superpages, no_incr_generationid,
+                           &state->vm_generationid_addr);
     if ( rc ) {
         LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "restoring domain");
         return ERROR_FAIL;
@@ -538,12 +553,23 @@ int libxl__domain_suspend_common(libxl__gc *gc, uint32_t domid, int fd,
     struct save_callbacks callbacks;
     struct suspendinfo si;
     int hvm, rc = ERROR_FAIL;
+    unsigned long vm_generationid_addr;
 
     switch (type) {
-    case LIBXL_DOMAIN_TYPE_HVM:
+    case LIBXL_DOMAIN_TYPE_HVM: {
+        char *path;
+        char *addr;
+
+        path = libxl__sprintf(gc, "%s/hvmloader/generation-id-address",
+                              libxl__xs_get_dompath(gc, domid));
+        addr = libxl__xs_read(gc, XBT_NULL, path);
+
+        vm_generationid_addr = (addr) ? strtoul(addr, NULL, 0) : 0;
         hvm = 1;
         break;
+    }
     case LIBXL_DOMAIN_TYPE_PV:
+        vm_generationid_addr = 0;
         hvm = 0;
         break;
     default:
@@ -581,7 +607,8 @@ int libxl__domain_suspend_common(libxl__gc *gc, uint32_t domid, int fd,
     callbacks.switch_qemu_logdirty = libxl__domain_suspend_common_switch_qemu_logdirty;
     callbacks.data = &si;
 
-    rc = xc_domain_save(ctx->xch, fd, domid, 0, 0, flags, &callbacks, hvm);
+    rc = xc_domain_save(ctx->xch, fd, domid, 0, 0, flags, &callbacks,
+                        hvm, vm_generationid_addr);
     if ( rc ) {
         LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "saving domain: %s",
                          si.guest_responded ?