[PATCH] x86/msr: add log messages to MSR state load error paths

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Some error paths in the MSR state loading logic don't contain error messages,
which makes debugging them quite hard without adding extra patches to print the
information.

Add two new log messages to the MSR state load path that print information
about the entry that failed to load.

No functional change intended.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/hvm/hvm.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 69a25571db8d..c71087f636c4 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -1598,10 +1598,19 @@ static int cf_check hvm_load_cpu_msrs(struct domain *d, 
hvm_domain_context_t *h)
             rc = guest_wrmsr(v, ctxt->msr[i].index, ctxt->msr[i].val);
 
             if ( rc != X86EMUL_OKAY )
+            {
+                printk(XENLOG_G_ERR
+                       "HVM%d.%d load MSR %#x with value %#lx failed: %d\n",
+                       d->domain_id, vcpuid, ctxt->msr[i].index,
+                       ctxt->msr[i].val, rc);
                 return -ENXIO;
+            }
             break;
 
         default:
+            printk(XENLOG_G_ERR
+                   "HVM%d.%d attempted load of unhandled MSR %#x\n",
+                   d->domain_id, vcpuid, ctxt->msr[i].index);
             return -ENXIO;
         }
     }
-- 
2.46.0