xen: allow HVM save/restore from different cpus

The hardware CPUID-levelling features level the feature flags but
don't change the CPU family/model/stepping.  Relax the HVM restore
check on family/model/stepping to printk but not veto the load, so
that VMs can be migrated between machines that have been
CPUID-levelled.

Signed-off-by: Tim Deegan <Tim.Deegan@citrix.com>
xen-unstable changeset:   21759:8b2453940dac
xen-unstable date:        Fri Jul 09 12:22:35 2010 +0100

diff --git a/xen/arch/x86/hvm/save.c b/xen/arch/x86/hvm/save.c
index 3fc24a02637681ec294a31e8f7b3eff4703249e6..bc1b51647c03523df9793790fc4ac6834122f8b3 100644 (file)
--- a/xen/arch/x86/hvm/save.c
+++ b/xen/arch/x86/hvm/save.c
@@ -55,10 +55,11 @@ int arch_hvm_load(struct domain *d, struct hvm_save_header *hdr)
     }
 
     cpuid(1, &eax, &ebx, &ecx, &edx);
-    /* TODO: need to define how big a difference is acceptable? */
-    if ( hdr->cpuid != eax )
-        gdprintk(XENLOG_WARNING, "HVM restore: saved CPUID (%#"PRIx32") "
-               "does not match host (%#"PRIx32").\n", hdr->cpuid, eax);
+    /* CPUs ought to match but with feature-masking they might not */
+    if ( (hdr->cpuid & ~0x0fUL) != (eax & ~0x0fUL) )
+        gdprintk(XENLOG_INFO, "HVM restore (%u): VM saved on one CPU "
+                 "(%#"PRIx32") and restored on another (%#"PRIx32").\n", 
+                 d->domain_id, hdr->cpuid, eax);
 
     /* Restore guest's preferred TSC frequency. */
     if ( hdr->gtsc_khz )