KVM: arm64: Forward safe PSCI SMCs coming from host

Forward the following PSCI SMCs issued by host to EL3 as they do not
require the hypervisor's intervention. This assumes that EL3 correctly
implements the PSCI specification.

Only function IDs implemented in Linux are included.

Where both 32-bit and 64-bit variants exist, it is assumed that the host
will always use the 64-bit variant.

 * SMCs that only return information about the system
   * PSCI_VERSION        - PSCI version implemented by EL3
   * PSCI_FEATURES       - optional features supported by EL3
   * AFFINITY_INFO       - power state of core/cluster
   * MIGRATE_INFO_TYPE   - whether Trusted OS can be migrated
   * MIGRATE_INFO_UP_CPU - resident core of Trusted OS
 * operations which do not affect the hypervisor
   * MIGRATE             - migrate Trusted OS to a different core
   * SET_SUSPEND_MODE    - toggle OS-initiated mode
 * system shutdown/reset
   * SYSTEM_OFF
   * SYSTEM_RESET
   * SYSTEM_RESET2
Signed-off-by: David Brazdil <dbrazdil@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201202184122.26046-19-dbrazdil@google.com

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

@@ -54,14 +54,50 @@ static bool is_psci_call(u64 func_id)
 	}
 }
 
+static unsigned long psci_call(unsigned long fn, unsigned long arg0,
+			       unsigned long arg1, unsigned long arg2)
+{
+	struct arm_smccc_res res;
+
+	arm_smccc_1_1_smc(fn, arg0, arg1, arg2, &res);
+	return res.a0;
+}
+
+static unsigned long psci_forward(struct kvm_cpu_context *host_ctxt)
+{
+	return psci_call(cpu_reg(host_ctxt, 0), cpu_reg(host_ctxt, 1),
+			 cpu_reg(host_ctxt, 2), cpu_reg(host_ctxt, 3));
+}
+
+static __noreturn unsigned long psci_forward_noreturn(struct kvm_cpu_context *host_ctxt)
+{
+	psci_forward(host_ctxt);
+	hyp_panic(); /* unreachable */
+}
+
 static unsigned long psci_0_1_handler(u64 func_id, struct kvm_cpu_context *host_ctxt)
 {
-	return PSCI_RET_NOT_SUPPORTED;
+	if ((func_id == kvm_host_psci_0_1_function_ids.cpu_off) ||
+	    (func_id == kvm_host_psci_0_1_function_ids.migrate))
+		return psci_forward(host_ctxt);
+	else
+		return PSCI_RET_NOT_SUPPORTED;
 }
 
 static unsigned long psci_0_2_handler(u64 func_id, struct kvm_cpu_context *host_ctxt)
 {
 	switch (func_id) {
+	case PSCI_0_2_FN_PSCI_VERSION:
+	case PSCI_0_2_FN_CPU_OFF:
+	case PSCI_0_2_FN64_AFFINITY_INFO:
+	case PSCI_0_2_FN64_MIGRATE:
+	case PSCI_0_2_FN_MIGRATE_INFO_TYPE:
+	case PSCI_0_2_FN64_MIGRATE_INFO_UP_CPU:
+		return psci_forward(host_ctxt);
+	case PSCI_0_2_FN_SYSTEM_OFF:
+	case PSCI_0_2_FN_SYSTEM_RESET:
+		psci_forward_noreturn(host_ctxt);
+		unreachable();
 	default:
 		return PSCI_RET_NOT_SUPPORTED;
 	}
@@ -70,6 +106,10 @@ static unsigned long psci_0_2_handler(u64 func_id, struct kvm_cpu_context *host_
 static unsigned long psci_1_0_handler(u64 func_id, struct kvm_cpu_context *host_ctxt)
 {
 	switch (func_id) {
+	case PSCI_1_0_FN_PSCI_FEATURES:
+	case PSCI_1_0_FN_SET_SUSPEND_MODE:
+	case PSCI_1_1_FN64_SYSTEM_RESET2:
+		return psci_forward(host_ctxt);
 	default:
 		return psci_0_2_handler(func_id, host_ctxt);
 	}