KVM: SVM: Use "standard" stgi() helper when disabling SVM

Now that kvm_rebooting is guaranteed to be true prior to disabling SVM
in an emergency, use the existing stgi() helper instead of open coding
STGI.  In effect, eat faults on STGI if and only if kvm_rebooting==true.

Link: https://lore.kernel.org/r/20230721201859.2307736-19-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/kvm/svm/svm.c

@@ -588,17 +588,10 @@ static inline void kvm_cpu_svm_disable(void)
 	rdmsrl(MSR_EFER, efer);
 	if (efer & EFER_SVME) {
 		/*
-		 * Force GIF=1 prior to disabling SVM to ensure INIT and NMI
-		 * aren't blocked, e.g. if a fatal error occurred between CLGI
-		 * and STGI.  Note, STGI may #UD if SVM is disabled from NMI
-		 * context between reading EFER and executing STGI.  In that
-		 * case, GIF must already be set, otherwise the NMI would have
-		 * been blocked, so just eat the fault.
+		 * Force GIF=1 prior to disabling SVM, e.g. to ensure INIT and
+		 * NMI aren't blocked.
 		 */
-		asm_volatile_goto("1: stgi\n\t"
-				  _ASM_EXTABLE(1b, %l[fault])
-				  ::: "memory" : fault);
-fault:
+		stgi();
 		wrmsrl(MSR_EFER, efer & ~EFER_SVME);
 	}
 }