lib: sbi: send a double trap SSE event to supervisor

In case the double trap handler is called and the double trap happened
in supervisor mode, send a double trap SSE event.

NOTE: this commit depends on the ratification of the new SSE event
id for double trap [1].

Link: https://lists.riscv.org/g/tech-prs/message/985 [1]
Signed-off-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Samuel Holland <samuel.holland@sifive.com>

include/sbi/sbi_ecall_interface.h

@@ -382,6 +382,7 @@ enum sbi_sse_state {
 
 /* SBI SSE Event IDs. */
 #define SBI_SSE_EVENT_LOCAL_RAS			0x00000000
+#define SBI_SSE_EVENT_LOCAL_DOUBLE_TRAP		0x00000001
 #define SBI_SSE_EVENT_LOCAL_PLAT_0_START	0x00004000
 #define SBI_SSE_EVENT_LOCAL_PLAT_0_END		0x00007fff
 #define SBI_SSE_EVENT_GLOBAL_RAS		0x00008000

lib/sbi/sbi_double_trap.c

@@ -26,5 +26,5 @@ int sbi_double_trap_handler(struct sbi_trap_context *tcntx)
 	if (prev_virt)
 		return sbi_trap_redirect(regs, trap);
 
-	return SBI_ENOTSUPP;
+	return sbi_sse_inject_event(SBI_SSE_EVENT_LOCAL_DOUBLE_TRAP);
 }

lib/sbi/sbi_sse.c

@@ -41,6 +41,7 @@
 
 static const uint32_t supported_events[] = {
 	SBI_SSE_EVENT_LOCAL_RAS,
+	SBI_SSE_EVENT_LOCAL_DOUBLE_TRAP,
 	SBI_SSE_EVENT_GLOBAL_RAS,
 	SBI_SSE_EVENT_LOCAL_PMU,
 	SBI_SSE_EVENT_LOCAL_SOFTWARE,