irqchip/apple-aic: Spit out ICH_MISR_EL2 value on spurious vGIC MI

It is all good and well to scream about spurious vGIC maintenance
interrupts. It would be even better to output the reason why, which
is already checked, but not printed out.

The unsuspecting kernel tinkerer thanks you.

Tested-by: Fuad Tabba <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>
Tested-by: Mark Brown <[e-mail]>
Link: https://msgid.link/[e-mail]
Signed-off-by: Oliver Upton <[e-mail]>

drivers/irqchip/irq-apple-aic.c

···
 	if (is_kernel_in_hyp_mode() &&
 	    (read_sysreg_s(SYS_ICH_HCR_EL2) & ICH_HCR_EL2_En) &&
 	    read_sysreg_s(SYS_ICH_MISR_EL2) != 0) {
+		u64 val;
+
 		generic_handle_domain_irq(aic_irqc->hw_domain,
 					  AIC_FIQ_HWIRQ(AIC_VGIC_MI));
 
 		if (unlikely((read_sysreg_s(SYS_ICH_HCR_EL2) & ICH_HCR_EL2_En) &&
-			     read_sysreg_s(SYS_ICH_MISR_EL2))) {
-			pr_err_ratelimited("vGIC IRQ fired and not handled by KVM, disabling.\n");
+			     (val = read_sysreg_s(SYS_ICH_MISR_EL2)))) {
+			pr_err_ratelimited("vGIC IRQ fired and not handled by KVM (MISR=%llx), disabling.\n",
+					   val);
 			sysreg_clear_set_s(SYS_ICH_HCR_EL2, ICH_HCR_EL2_En, 0);
 		}
 	}