[PATCH for 4.6 v3 2/3] xl/libxl: disallow saving a guest with vNUMA configured

[Wei Liu <wei.liu2@citrix.com>]

This is because the migration stream does not preserve node information.

Note this is not a regression for migration v2 vs legacy migration
because neither of them preserve node information.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
Cc: andrew.cooper3@citrix.com

v3:
1. Update manpage, code comment and commit message.
2. *Don't* check if nomigrate is set.
---
 docs/man/xl.cfg.pod.5   |  2 ++
 tools/libxl/libxl_dom.c | 14 ++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5
index 80e51bb..555f8ba 100644
--- a/docs/man/xl.cfg.pod.5
+++ b/docs/man/xl.cfg.pod.5
@@ -263,6 +263,8 @@ virtual node.
 
 Note that virtual NUMA for PV guest is not yet supported, because
 there is an issue with cpuid handling that affects PV virtual NUMA.
+Further more, guest with virtual NUMA cannot be saved or migrated
+because migration stream does not preserve node information.
 
 Each B<VNODE_SPEC> is a list, which has a form of
 "[VNODE_CONFIG_OPTION,VNODE_CONFIG_OPTION, ... ]"  (without quotes).
diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index c2518a3..a4d37dc 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -24,6 +24,7 @@
 #include <xen/hvm/hvm_info_table.h>
 #include <xen/hvm/hvm_xs_strings.h>
 #include <xen/hvm/e820.h>
+#include <xen/errno.h>
 
 libxl_domain_type libxl__domain_type(libxl__gc *gc, uint32_t domid)
 {
@@ -1612,6 +1613,7 @@ void libxl__domain_save(libxl__egc *egc, libxl__domain_suspend_state *dss)
     const libxl_domain_remus_info *const r_info = dss->remus;
     libxl__srm_save_autogen_callbacks *const callbacks =
         &dss->sws.shs.callbacks.save.a;
+    unsigned int nr_vnodes = 0, nr_vmemranges = 0, nr_vcpus = 0;
 
     dss->rc = 0;
     logdirty_init(&dss->logdirty);
@@ -1636,6 +1638,18 @@ void libxl__domain_save(libxl__egc *egc, libxl__domain_suspend_state *dss)
           | (debug ? XCFLAGS_DEBUG : 0)
           | (dss->hvm ? XCFLAGS_HVM : 0);
 
+    /* Disallow saving a guest with vNUMA configured because migration
+     * stream does not preserve node information.
+     */
+    rc = xc_domain_getvnuma(CTX->xch, domid, &nr_vnodes, &nr_vmemranges,
+                            &nr_vcpus, NULL, NULL, NULL);
+    assert(rc == -1 && (errno == XEN_ENOBUFS || errno == XEN_EOPNOTSUPP));
+    if (errno == XEN_ENOBUFS && nr_vnodes) {
+        LOG(ERROR, "Cannot save a guest with vNUMA configured");
+        rc = ERROR_FAIL;
+        goto out;
+    }
+
     dss->guest_evtchn.port = -1;
     dss->guest_evtchn_lockfd = -1;
     dss->guest_responded = 0;
-- 
2.1.4