xen/riscv: introduce trap_init()

Note that trap_init() isn't declared with the __init attribute to
avoid removing __init when multi-CPU support for Xen is added.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/arch/riscv/include/asm/traps.h

@@ -9,6 +9,7 @@
 
 void do_trap(struct cpu_user_regs *cpu_regs);
 void handle_trap(void);
+void trap_init(void);
 
 #endif /* __ASSEMBLY__ */
 

xen/arch/riscv/setup.c

@@ -8,6 +8,7 @@
 #include <public/version.h>
 
 #include <asm/early_printk.h>
+#include <asm/traps.h>
 
 void arch_get_xen_caps(xen_capabilities_info_t *info)
 {
@@ -23,6 +24,8 @@ void __init noreturn start_xen(unsigned long bootcpu_id,
 {
     remove_identity_mapping();
 
+    trap_init();
+
     printk("All set up\n");
 
     for ( ;; )

xen/arch/riscv/traps.c

@@ -12,6 +12,18 @@
 #include <asm/riscv_encoding.h>
 #include <asm/traps.h>
 
+/*
+ * Initialize the trap handling.
+ *
+ * The function is called after MMU is enabled.
+ */
+void trap_init(void)
+{
+    unsigned long addr = (unsigned long)&handle_trap;
+
+    csr_write(CSR_STVEC, addr);
+}
+
 static const char *decode_trap_cause(unsigned long cause)
 {
     static const char *const trap_causes[] = {