[Xen-changelog] [xen master] libxc: use an explicit check for PV MSRs in xc_domain_save()

[patchbot@xxxxxxx]

commit db24f7f0123c3103e0d7860a7dc3be84463d1814
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Tue Jun 10 16:58:47 2014 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Jun 10 16:58:47 2014 +0200

    libxc: use an explicit check for PV MSRs in xc_domain_save()
    
    Migrating PV domains using MSRs is not supported.  This uses the new
    XEN_DOMCTL_get_vcpu_msrs and will fail the migration with an explicit error.
    
    This is an improvement upon the current failure of
      "No extended context for VCPUxx (ENOBUFS)"
    
    Support for migrating PV domains which are using MSRs will be included in 
the
    migration v2 work.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
---
 tools/libxc/xc_domain_save.c |   20 ++++++++++++++++++++
 1 files changed, 20 insertions(+), 0 deletions(-)

diff --git a/tools/libxc/xc_domain_save.c b/tools/libxc/xc_domain_save.c
index acf3685..778cbde 100644
--- a/tools/libxc/xc_domain_save.c
+++ b/tools/libxc/xc_domain_save.c
@@ -1995,6 +1995,26 @@ int xc_domain_save(xc_interface *xch, int io_fd, 
uint32_t dom, uint32_t max_iter
             goto out;
         }
 
+        /* Check there are no PV MSRs in use. */
+        domctl.cmd = XEN_DOMCTL_get_vcpu_msrs;
+        domctl.domain = dom;
+        memset(&domctl.u, 0, sizeof(domctl.u));
+        domctl.u.vcpu_msrs.vcpu = i;
+        domctl.u.vcpu_msrs.msr_count = 0;
+        set_xen_guest_handle_raw(domctl.u.vcpu_msrs.msrs, (void*)1);
+
+        if ( xc_domctl(xch, &domctl) < 0 )
+        {
+            if ( errno == ENOBUFS )
+            {
+                errno = EOPNOTSUPP;
+                PERROR("Unable to migrate PV guest using MSRs (yet)");
+            }
+            else
+                PERROR("Error querying maximum number of MSRs for VCPU%d", i);
+            goto out;
+        }
+
         /* Start to fetch CPU eXtended States */
         /* Get buffer size first */
         domctl.cmd = XEN_DOMCTL_getvcpuextstate;
--
generated by git-patchbot for /home/xen/git/xen.git#master

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