Revert "KVM: x86: expose MSR_TSC_AUX to userspace"

This reverts commit a79ed0ed, which was
commit 9dbe6cf9 upstream.  It depends on
several other large commits to work, and without them causes a regression.

References: https://bugzilla.redhat.com/show_bug.cgi?id=1408333Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Eric Wheeler <kvm@lists.ewheeler.net>

arch/x86/kvm/x86.c

@@ -892,7 +892,7 @@ static u32 msrs_to_save[] = {
 	MSR_CSTAR, MSR_KERNEL_GS_BASE, MSR_SYSCALL_MASK, MSR_LSTAR,
 #endif
 	MSR_IA32_TSC, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA,
-	MSR_IA32_FEATURE_CONTROL, MSR_IA32_BNDCFGS, MSR_TSC_AUX,
+	MSR_IA32_FEATURE_CONTROL, MSR_IA32_BNDCFGS
 };
 
 static unsigned num_msrs_to_save;
@@ -3994,17 +3994,16 @@ static void kvm_init_msr_list(void)
 
 		/*
 		 * Even MSRs that are valid in the host may not be exposed
-		 * to the guests in some cases.
+		 * to the guests in some cases.  We could work around this
+		 * in VMX with the generic MSR save/load machinery, but it
+		 * is not really worthwhile since it will really only
+		 * happen with nested virtualization.
 		 */
 		switch (msrs_to_save[i]) {
 		case MSR_IA32_BNDCFGS:
 			if (!kvm_x86_ops->mpx_supported())
 				continue;
 			break;
-		case MSR_TSC_AUX:
-			if (!kvm_x86_ops->rdtscp_supported())
-				continue;
-			break;
 		default:
 			break;
 		}