Intercept guest reads of MSR_IA32_MCG_CAP and limit the number of memory banks
reported to one.
This prevents us from trying to read status of non-existent banks when migrated
to a machine
with fewer banks.
Signed-off-by: Ben Guthro
Signed-off-by: David Lively <dlively@xxxxxxxxxxxxxxx>
diff -r 4eea7c9b3bf2 xen/arch/x86/hvm/svm/svm.c
--- a/xen/arch/x86/hvm/svm/svm.c Thu Aug 02 08:59:43 2007 -0400
+++ b/xen/arch/x86/hvm/svm/svm.c Thu Aug 02 08:59:43 2007 -0400
@@ -2162,7 +2162,19 @@ static void svm_do_msr_access(
/* No point in letting the guest see real MCEs */
msr_content = 0;
break;
-
+ case MSR_IA32_MCG_CAP:
+ if ( rdmsr_safe(ecx, regs->eax, regs->edx) == 0 ) {
+ /*
+ * Report at most one memory bank so migration to a machine
with
+ * fewer banks doesn't cause guest GPFs when the guest tries
to read the
+ * (now, after migration) non-existent banks' MSRs.
+ */
+ regs->eax = (regs->eax & ~0xFF) | !!(regs->eax & 0xFF);
+ goto done;
+ }
+ gdprintk(XENLOG_ERR, "%s: rdmsr_safe(MCG_CAP) failed!\n",
__FUNCTION__);
+ svm_inject_exception(v, TRAP_gp_fault, 1, 0);
+ return;
default:
if ( rdmsr_hypervisor_regs(ecx, &eax, &edx) ||
rdmsr_safe(ecx, eax, edx) == 0 )
diff -r 4eea7c9b3bf2 xen/arch/x86/hvm/vmx/vmx.c
--- a/xen/arch/x86/hvm/vmx/vmx.c Thu Aug 02 08:59:43 2007 -0400
+++ b/xen/arch/x86/hvm/vmx/vmx.c Thu Aug 02 09:14:06 2007 -0400
@@ -2754,6 +2754,19 @@ static int vmx_do_msr_read(struct cpu_us
/* No point in letting the guest see real MCEs */
msr_content = 0;
break;
+ case MSR_IA32_MCG_CAP:
+ if ( rdmsr_safe(ecx, regs->eax, regs->edx) == 0 ) {
+ /*
+ * Report only a single memory bank so migration to a machine with
+ * fewer banks doesn't cause guest GPFs when the guest tries to
read the
+ * (now, after migration) non-existent banks' MSRs.
+ */
+ regs->eax = (regs->eax & ~0xFF) | !!(regs->eax & 0xFF);
+ goto done;
+ }
+ gdprintk(XENLOG_ERR, "%s: rdmsr_safe(MCG_CAP) failed!\n",
__FUNCTION__);
+ vmx_inject_hw_exception(v, TRAP_gp_fault, 0);
+ return 0;
default:
switch ( long_mode_do_msr_read(regs) )
{
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