[PATCH v2] lib: sbi_trap: Redirect exception based on hedeleg

[dramforever]

HS-mode software can choose what exceptions to delegate to VS-mode using
the hedeleg CSR. Synthetic VS/VU-mode exceptions should also honor
hedeleg. They should be redirected to VS-mode if and only if delegated
by HS-mode.

Signed-off-by: dramforever <dramforever at live.com>
---

Changes since v1:
 - Use BIT() macro instead of (1 << trap->cause)

 lib/sbi/sbi_trap.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/lib/sbi/sbi_trap.c b/lib/sbi/sbi_trap.c
index 2c509e5..a54a131 100644
--- a/lib/sbi/sbi_trap.c
+++ b/lib/sbi/sbi_trap.c
@@ -99,17 +99,14 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
 	if (prev_mode != PRV_S && prev_mode != PRV_U)
 		return SBI_ENOTSUPP;
 
-	/* For certain exceptions from VS/VU-mode we redirect to VS-mode */
+	/* If exceptions came from VS/VU-mode, redirect to VS-mode if
+	 * delegated in hedeleg
+	 */
 	if (misa_extension('H') && prev_virt) {
-		switch (trap->cause) {
-		case CAUSE_FETCH_PAGE_FAULT:
-		case CAUSE_LOAD_PAGE_FAULT:
-		case CAUSE_STORE_PAGE_FAULT:
+		if (trap->cause < __riscv_xlen &&
+		    csr_read(CSR_HEDELEG) & BIT(trap->cause)) {
 			next_virt = TRUE;
-			break;
-		default:
-			break;
-		};
+		}
 	}
 
 	/* Update MSTATUS MPV bits */
-- 
2.36.1