From: Keir Fraser <keir.fraser@citrix.com>
Date: Fri, 9 Jul 2010 11:22:35 +0000 (+0100)
Subject: xen: allow HVM save/restore from different cpus
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~11823
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=3130f964bad10c85c17b1e28ed9b278745a905b9;p=xen.git

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>
---

diff --git a/xen/arch/x86/hvm/save.c b/xen/arch/x86/hvm/save.c
index 3fc24a0263..bc1b51647c 100644
--- 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 )