KVM: arm64: Intercept host's SYSTEM_SUSPEND PSCI SMCs

Add a handler of SYSTEM_SUSPEND host PSCI SMCs. The semantics are
equivalent to CPU_SUSPEND, typically called on the last online CPU.
Reuse the same entry point and boot args struct as CPU_SUSPEND.
Signed-off-by: David Brazdil <dbrazdil@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201202184122.26046-24-dbrazdil@google.com

arch/arm64/kvm/hyp/nvhe/hyp-init.S

@@ -151,7 +151,7 @@ SYM_CODE_START(kvm_hyp_cpu_entry)
 SYM_CODE_END(kvm_hyp_cpu_entry)
 
 /*
- * PSCI CPU_SUSPEND entry point
+ * PSCI CPU_SUSPEND / SYSTEM_SUSPEND entry point
  *
  * x0: struct kvm_nvhe_init_params PA
  */

arch/arm64/kvm/hyp/nvhe/psci-relay.c

@@ -201,6 +201,30 @@ static int psci_cpu_suspend(u64 func_id, struct kvm_cpu_context *host_ctxt)
 			 __hyp_pa(init_params));
 }
 
+static int psci_system_suspend(u64 func_id, struct kvm_cpu_context *host_ctxt)
+{
+	DECLARE_REG(unsigned long, pc, host_ctxt, 1);
+	DECLARE_REG(unsigned long, r0, host_ctxt, 2);
+
+	struct psci_boot_args *boot_args;
+	struct kvm_nvhe_init_params *init_params;
+
+	boot_args = this_cpu_ptr(hyp_symbol_addr(suspend_args));
+	init_params = this_cpu_ptr(hyp_symbol_addr(kvm_init_params));
+
+	/*
+	 * No need to acquire a lock before writing to boot_args because a core
+	 * can only suspend itself. Racy CPU_ON calls use a separate struct.
+	 */
+	boot_args->pc = pc;
+	boot_args->r0 = r0;
+
+	/* Will only return on error. */
+	return psci_call(func_id,
+			 __hyp_pa(hyp_symbol_addr(kvm_hyp_cpu_resume)),
+			 __hyp_pa(init_params), 0);
+}
+
 asmlinkage void __noreturn kvm_host_psci_cpu_entry(bool is_cpu_on)
 {
 	struct psci_boot_args *boot_args;
@@ -265,6 +289,8 @@ static unsigned long psci_1_0_handler(u64 func_id, struct kvm_cpu_context *host_
 	case PSCI_1_0_FN_SET_SUSPEND_MODE:
 	case PSCI_1_1_FN64_SYSTEM_RESET2:
 		return psci_forward(host_ctxt);
+	case PSCI_1_0_FN64_SYSTEM_SUSPEND:
+		return psci_system_suspend(func_id, host_ctxt);
 	default:
 		return psci_0_2_handler(func_id, host_ctxt);
 	}