feat(spm_mm): add support to save and restore fp regs

Add the support to save Nwd's floating point registers before switching
to SEL0 and then restore it after coming out of it. Emit a warning
message if SPM_MM is built with CTX_INCLUDE_FPREGS == 0

There is no need to save FP registers of SEL0 because secure partitions
run to completion.

This change is used to prevent context corruption if secure partition
enabled and Nwd decide to use floating point registers.

Signed-off-by: Nishant Sharma <nishant.sharma@arm.com>
Change-Id: I1eea16ea2311a4f00a806ea72c118752821b9abb

services/std_svc/spm/spm_mm/spm_mm.mk

@@ -16,6 +16,9 @@ endif
 ifeq (${ENABLE_SME_FOR_NS},1)
         $(error "Error: SPM_MM is not compatible with ENABLE_SME_FOR_NS")
 endif
+ifeq (${CTX_INCLUDE_FPREGS},0)
+        $(warning "Warning: SPM_MM: CTX_INCLUDE_FPREGS is set to 0")
+endif
 
 SPM_MM_SOURCES	:=	$(addprefix services/std_svc/spm/spm_mm/,	\
 			${ARCH}/spm_mm_shim_exceptions.S		\

services/std_svc/spm/spm_mm/spm_mm_main.c

@@ -190,6 +190,14 @@ uint64_t spm_mm_sp_call(uint32_t smc_fid, uint64_t x1, uint64_t x2, uint64_t x3)
 	uint64_t rc;
 	sp_context_t *sp_ptr = &sp_ctx;
 
+#if CTX_INCLUDE_FPREGS
+	/*
+	 * SP runs to completion, no need to restore FP registers of secure context.
+	 * Save FP registers only for non secure context.
+	 */
+	fpregs_context_save(get_fpregs_ctx(cm_get_context(NON_SECURE)));
+#endif
+
 	/* Wait until the Secure Partition is idle and set it to busy. */
 	sp_state_wait_switch(sp_ptr, SP_STATE_IDLE, SP_STATE_BUSY);
 
@@ -208,6 +216,14 @@ uint64_t spm_mm_sp_call(uint32_t smc_fid, uint64_t x1, uint64_t x2, uint64_t x3)
 	assert(sp_ptr->state == SP_STATE_BUSY);
 	sp_state_set(sp_ptr, SP_STATE_IDLE);
 
+#if CTX_INCLUDE_FPREGS
+	/*
+	 * SP runs to completion, no need to save FP registers of secure context.
+	 * Restore only non secure world FP registers.
+	 */
+	fpregs_context_restore(get_fpregs_ctx(cm_get_context(NON_SECURE)));
+#endif
+
 	return rc;
 }