arm, arm64: Emulate PSCI service PSCI_CPU_SUSPEND

This is a mandatory service with PSCI v0.2+, and if the root cell was
using it prior to enabling Jailhouse, just returning an error, like we
do so far, will send the CPUs into a busy loop.

Implement the minimum of this service by sending the CPU into a wfi, but
only if there are no interrupt waiting to be injected. We better check
for physical interrupts after the wfi to reduce world switches and,
thus, event delivery latencies.

CC: Ralf Ramsauer <ralf@ramses-pyramidenbau.de>
CC: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Tested-by: Ralf Ramsauer <ralf@ramses-pyramidenbau.de>

hypervisor/arch/arm-common/include/asm/psci.h

@@ -14,6 +14,8 @@
 #define _JAILHOUSE_ASM_PSCI_H
 
 #define PSCI_VERSION			0x84000000
+#define PSCI_CPU_SUSPEND_32		0x84000001
+#define PSCI_CPU_SUSPEND_64		0xc4000001
 #define PSCI_CPU_OFF			0x84000002
 #define PSCI_CPU_ON_32			0x84000003
 #define PSCI_CPU_ON_64			0xc4000003

hypervisor/arch/arm-common/psci.c

@@ -79,6 +79,14 @@ long psci_dispatch(struct trap_context *ctx)
 		/* Major[31:16], minor[15:0] */
 		return 2;
 
+	case PSCI_CPU_SUSPEND_32:
+	case PSCI_CPU_SUSPEND_64:
+		if (!irqchip_has_pending_irqs()) {
+			asm volatile("wfi" : : : "memory");
+			irqchip_handle_irq(cpu_data);
+		}
+		return 0;
+
 	case PSCI_CPU_OFF:
 	case PSCI_CPU_OFF_V0_1_UBOOT:
 		arm_cpu_park();