Re: [Xen-devel] [PATCH for 4.6 v4 2/3] xl/libxl: disallow saving a guest with vNUMA configured

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Sep 11, 2015 at 03:00:35PM +0100, Ian Campbell wrote:
> On Fri, 2015-09-11 at 14:50 +0100, Wei Liu wrote:
> > +    /* Disallow saving a guest with vNUMA configured because migration
> > +     * stream does not preserve node information.
> > +     *
> > +     * Do not differentiate "no vnuma configuration" from "empty vnuma
> > +     * configuration".
> > +     */
> > +    rc = xc_domain_getvnuma(CTX->xch, domid, &nr_vnodes, &nr_vmemranges,
> > +                            &nr_vcpus, NULL, NULL, NULL);
> > +    if (rc != -1 || errno == XEN_ENOBUFS) {
> 
> This is not as we discussed, it is neither what I proposed nor what you
> (incorrectly IMHO) corrected it to be in the previous thread.
> 

To avoid spamming the list I attach the updated version here.

Tested with saving guests with / without vnuma configuration.

---8<---
From 0c286535e998b62dbe0e35be4c9366fb8dc0934d Mon Sep 17 00:00:00 2001
From: Wei Liu <wei.liu2@xxxxxxxxxx>
Date: Wed, 9 Sep 2015 17:11:24 +0100
Subject: [PATCH] xl/libxl: disallow saving a guest with vNUMA configured

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@xxxxxxxxxx>
---
Cc: andrew.cooper3@xxxxxxxxxx

v4:
1. Don't differentiate "no vnuma" from "empty vnuma".

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 | 16 ++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5
index c6345b8..157c855 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..72fce21 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 +1638,20 @@ 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.
+     *
+     * Do not differentiate "no vnuma configuration" from "empty vnuma
+     * configuration".
+     */
+    rc = xc_domain_getvnuma(CTX->xch, domid, &nr_vnodes, &nr_vmemranges,
+                            &nr_vcpus, NULL, NULL, NULL);
+    if (rc != -1 || errno != XEN_EOPNOTSUPP) {
+        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


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