Introduce ARM SiP service to switch execution state

In AArch64, privileged exception levels control the execution state
(a.k.a. register width) of the immediate lower Exception Level; i.e.
whether the lower exception level executes in AArch64 or AArch32 state.
For an exception level to have its execution state changed at run time,
it must request the change by raising a synchronous exception to the
higher exception level.

This patch implements and adds such a provision to the ARM SiP service,
by which an immediate lower exception level can request to switch its
execution state. The execution state is switched if the request is:

  - raised from non-secure world;

  - raised on the primary CPU, before any secondaries are brought online
    with CPU_ON PSCI call;

  - raised from an exception level immediately below EL3: EL2, if
    implemented; otherwise NS EL1.

If successful, the SMC doesn't return to the caller, but to the entry
point supplied with the call. Otherwise, the caller will observe the SMC
returning with STATE_SW_E_DENIED code. If ARM Trusted Firmware is built
for AArch32, the feature is not supported, and the call will always
fail.

For the ARM SiP service:

  - Add SMC function IDs for both AArch32 and AArch64;
  - Increment the SiP service minor version to 2;
  - Adjust the number of supported SiP service calls.

Add documentation for ARM SiP service.

Fixes ARM-software/tf-issues#436

Change-Id: I4347f2d6232e69fbfbe333b340fcd0caed0a4cea
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

5 files changed, 21 insertions, 3 deletions

diff --git a/include/lib/aarch64/arch.h b/include/lib/aarch64/arch.h
index 834434ee..efb6b919 100644
--- a/include/lib/aarch64/arch.h
+++ b/include/lib/aarch64/arch.h
@@ -211,7 +211,8 @@
 #define MDCR_DEF_VAL		(MDCR_SDD_BIT | MDCR_SPD32(MDCR_SPD32_DISABLE))
 
 /* HCR definitions */
-#define HCR_RW_BIT		(1ull << 31)
+#define HCR_RW_SHIFT		31
+#define HCR_RW_BIT		(1ull << HCR_RW_SHIFT)
 #define HCR_AMO_BIT		(1 << 5)
 #define HCR_IMO_BIT		(1 << 4)
 #define HCR_FMO_BIT		(1 << 3)
diff --git a/include/lib/el3_runtime/context_mgmt.h b/include/lib/el3_runtime/context_mgmt.h
index 31bf6816..6c43c66c 100644
--- a/include/lib/el3_runtime/context_mgmt.h
+++ b/include/lib/el3_runtime/context_mgmt.h
@@ -33,6 +33,8 @@
 
 #ifndef AARCH32
 #include <arch.h>
+#include <assert.h>
+#include <stdint.h>
 #endif
 
 /*******************************************************************************
diff --git a/include/lib/psci/psci_lib.h b/include/lib/psci/psci_lib.h
index 2169d6de..b02e7abf 100644
--- a/include/lib/psci/psci_lib.h
+++ b/include/lib/psci/psci_lib.h
@@ -106,6 +106,7 @@ u_register_t psci_smc_handler(uint32_t smc_fid,
 			  void *handle,
 			  u_register_t flags);
 int psci_setup(const psci_lib_args_t *lib_args);
+int psci_secondaries_brought_up(void);
 void psci_warmboot_entrypoint(void);
 void psci_register_spd_pm_hook(const spd_pm_ops_t *pm);
 void psci_prepare_next_non_secure_ctx(
diff --git a/include/plat/arm/common/arm_sip_svc.h b/include/plat/arm/common/arm_sip_svc.h
index 640bbafc..f3eac318 100644
--- a/include/plat/arm/common/arm_sip_svc.h
+++ b/include/plat/arm/common/arm_sip_svc.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2016-2017, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
@@ -38,8 +38,11 @@
 /*					0x8200ff02 is reserved */
 #define ARM_SIP_SVC_VERSION		0x8200ff03
 
+/* Function ID for requesting state switch of lower EL */
+#define ARM_SIP_SVC_EXE_STATE_SWITCH	0x82000020
+
 /* ARM SiP Service Calls version numbers */
 #define ARM_SIP_SVC_VERSION_MAJOR		0x0
-#define ARM_SIP_SVC_VERSION_MINOR		0x1
+#define ARM_SIP_SVC_VERSION_MINOR		0x2
 
 #endif /* __ARM_SIP_SVC_H__ */
diff --git a/include/plat/arm/common/plat_arm.h b/include/plat/arm/common/plat_arm.h
index 8ea32b9a..2b7e16ce 100644
--- a/include/plat/arm/common/plat_arm.h
+++ b/include/plat/arm/common/plat_arm.h
@@ -124,6 +124,9 @@ void arm_setup_page_tables(uintptr_t total_base,
 
 #endif /* __ARM_RECOM_STATE_ID_ENC__ */
 
+/* ARM State switch error codes */
+#define STATE_SW_E_PARAM		(-2)
+#define STATE_SW_E_DENIED		(-3)
 
 /* IO storage utility functions */
 void arm_io_setup(void);
@@ -230,4 +233,12 @@ const mmap_region_t *plat_arm_get_mmap(void);
 /* Allow platform to override psci_pm_ops during runtime */
 const plat_psci_ops_t *plat_arm_psci_override_pm_ops(plat_psci_ops_t *ops);
 
+/* Execution state switch in ARM platforms */
+int arm_execution_state_switch(unsigned int smc_fid,
+		uint32_t pc_hi,
+		uint32_t pc_lo,
+		uint32_t cookie_hi,
+		uint32_t cookie_lo,
+		void *handle);
+
 #endif /* __PLAT_ARM_H__ */