KVM: arm64: selftests: Ensure pending interrupts are handled in arch_timer test

Break up the asm instructions poking daifclr and daifset to handle
interrupts. R_RBZYL specifies pending interrupts will be handle after
context synchronization events such as an ISB.

Introduce a function wrapper for the WFI instruction.

Signed-off-by: Colton Lewis <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Marc Zyngier <[e-mail]>

tools/testing/selftests/kvm/aarch64/vgic_irq.c

···
 	KVM_INJECT_MULTI(cmd, first_intid, num);
 
 	while (irq_handled < num) {
-		asm volatile("wfi\n"
-			     "msr daifclr, #2\n"
-			     /* handle IRQ */
-			     "msr daifset, #2\n"
-			     : : : "memory");
+		wfi();
+		local_irq_enable();
+		isb(); /* handle IRQ */
+		local_irq_disable();
 	}
-	asm volatile("msr daifclr, #2" : : : "memory");
+	local_irq_enable();
 
 	GUEST_ASSERT_EQ(irq_handled, num);
 	for (i = first_intid; i < num + first_intid; i++)

tools/testing/selftests/kvm/include/aarch64/processor.h

···
 	       uint64_t arg2, uint64_t arg3, uint64_t arg4, uint64_t arg5,
 	       uint64_t arg6, struct arm_smccc_res *res);
 
+/* Execute a Wait For Interrupt instruction. */
+void wfi(void);
+
 #endif /* SELFTEST_KVM_PROCESSOR_H */

tools/testing/selftests/kvm/lib/aarch64/processor.c

···
 	sparsebit_set_num(vm->vpages_valid, 0,
 			  (1ULL << vm->va_bits) >> vm->page_shift);
 }
+
+/* Helper to call wfi instruction. */
+void wfi(void)
+{
+	asm volatile("wfi");
+}