Re: [Xen-devel] [PATCH for 4.6 v2 3/3] xl/libxl: disallow saving a guest with vNUMA configured

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Sep 09, 2015 at 01:17:40PM -0400, Boris Ostrovsky wrote:
> On 09/09/2015 01:03 PM, Wei Liu wrote:
> >This is due to migration v2 frame record doesn't contain node
> >information.
> >
> >Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> >---
> >Cc: andrew.cooper3@xxxxxxxxxx
> >---
> >  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..dbd0700 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 node information of guest frames is not preserved.
> 
> Should we also issue a warning during startup if nomigrate is not set?
> 

<dig dig>

Ah, there is such option. I can certainly give a warning. The only
problem is it seems to be stale in libxl, there is no code that checks
that! I can still migrate a guest even with nomigrate set to true.

Maybe someone with more knowledge about that option can lecture me on
what that does? The manpage says it *enables* certain feature? Does that
actually mean *make available*?

Wei.


> -boris
> 
> >  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..5dc4d3a 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
> >+     * v2 record doesn't contain node information for guest frame.
> >+     */
> >+    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;

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