Author: neel
Date: Sat Dec 20 19:47:51 2014
New Revision: 275965
URL: https://svnweb.freebsd.org/changeset/base/275965
Log:
Emulate writes to the IA32_MISC_ENABLE MSR.
PR: 196093
Reported by: db
Tested by: db
Discussed with: grehan
MFC after: 1 week
Modified:
head/sys/amd64/vmm/intel/vmx_msr.c
Modified: head/sys/amd64/vmm/intel/vmx_msr.c
==============================================================================
--- head/sys/amd64/vmm/intel/vmx_msr.c Sat Dec 20 19:41:31 2014
(r275964)
+++ head/sys/amd64/vmm/intel/vmx_msr.c Sat Dec 20 19:47:51 2014
(r275965)
@@ -376,9 +376,31 @@ vmx_rdmsr(struct vmx *vmx, int vcpuid, u
int
vmx_wrmsr(struct vmx *vmx, int vcpuid, u_int num, uint64_t val, bool *retu)
{
- int error = 0;
-
+ uint64_t changed;
+ int error;
+
+ error = 0;
switch (num) {
+ case MSR_IA32_MISC_ENABLE:
+ changed = val ^ misc_enable;
+ /*
+ * If the host has disabled the NX feature then the guest
+ * also cannot use it. However, a Linux guest will try to
+ * enable the NX feature by writing to the MISC_ENABLE MSR.
+ *
+ * This can be safely ignored because the memory management
+ * code looks at CPUID.80000001H:EDX.NX to check if the
+ * functionality is actually enabled.
+ */
+ changed &= ~(1UL << 34);
+
+ /*
+ * Punt to userspace if any other bits are being modified.
+ */
+ if (changed)
+ error = EINVAL;
+
+ break;
default:
error = EINVAL;
break;
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