x86/jailhouse: Wire up IOAPIC for legacy UART ports

The typical I/O interrupts in non-root cells are MSI-based. However, the
platform UARTs do not support MSI. In order to run a non-root cell that
shall use one of them, the standard IOAPIC must be registered and 1:1
routing for IRQ 3 and 4 set up.

If an IOAPIC is not available, the boot loader clears standard_ioapic in
the setup data, so registration is skipped. If the guest is not allowed to
to use one of those pins, Jailhouse will simply ignore the access.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: jailhouse-dev@googlegroups.com
Link: https://lkml.kernel.org/r/90d942dda9d48a8046e00bb3c1bb6757c83227be.1511770314.git.jan.kiszka@siemens.com

arch/x86/kernel/jailhouse.c

@@ -15,6 +15,7 @@
 #include <asm/cpu.h>
 #include <asm/hypervisor.h>
 #include <asm/i8259.h>
+#include <asm/irqdomain.h>
 #include <asm/reboot.h>
 #include <asm/setup.h>
 
@@ -52,6 +53,15 @@ static unsigned long jailhouse_get_tsc(void)
 
 static void __init jailhouse_get_smp_config(unsigned int early)
 {
+	struct ioapic_domain_cfg ioapic_cfg = {
+		.type = IOAPIC_DOMAIN_STRICT,
+		.ops = &mp_ioapic_irqdomain_ops,
+	};
+	struct mpc_intsrc mp_irq = {
+		.type = MP_INTSRC,
+		.irqtype = mp_INT,
+		.irqflag = MP_IRQPOL_ACTIVE_HIGH | MP_IRQTRIG_EDGE,
+	};
 	unsigned int cpu;
 
 	if (x2apic_enabled()) {
@@ -77,6 +87,17 @@ static void __init jailhouse_get_smp_config(unsigned int early)
 	}
 
 	smp_found_config = 1;
+
+	if (setup_data.standard_ioapic) {
+		mp_register_ioapic(0, 0xfec00000, gsi_top, &ioapic_cfg);
+
+		/* Register 1:1 mapping for legacy UART IRQs 3 and 4 */
+		mp_irq.srcbusirq = mp_irq.dstirq = 3;
+		mp_save_irq(&mp_irq);
+
+		mp_irq.srcbusirq = mp_irq.dstirq = 4;
+		mp_save_irq(&mp_irq);
+	}
 }
 
 static void jailhouse_no_restart(void)