[PATCH v2 2/8] lib: sbi_domain: allow specifying inaccessible region

[Yu-Chien Peter Lin]

According to the RISC‑V Privileged Specification, SmePMP
regions that grant no access in any privilege mode are
valid. Allow such regions to be specified.

Signed-off-by: Yu-Chien Peter Lin <peter.lin at sifive.com>
---
 lib/sbi/sbi_domain.c | 12 +++++++++++-
 lib/sbi/sbi_hart.c   |  4 ----
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/lib/sbi/sbi_domain.c b/lib/sbi/sbi_domain.c
index 1fa56b6a..89250d4c 100644
--- a/lib/sbi/sbi_domain.c
+++ b/lib/sbi/sbi_domain.c
@@ -126,7 +126,17 @@ unsigned int sbi_domain_get_smepmp_flags(struct sbi_domain_memregion *reg)
 {
 	unsigned int pmp_flags = 0;
 
-	if (SBI_DOMAIN_MEMREGION_IS_SHARED(reg->flags)) {
+	if ((reg->flags & SBI_DOMAIN_MEMREGION_ACCESS_MASK) == 0) {
+		/*
+		 * Region is inaccessible in all privilege modes.
+		 *
+		 * SmePMP allows two encodings for an inaccessible region:
+		 *   - pmpcfg.LRWX = 0000 (Inaccessible region)
+		 *   - pmpcfg.LRWX = 1000 (Locked inaccessible region)
+		 * We use the first encoding here.
+		 */
+		return 0;
+	} else if (SBI_DOMAIN_MEMREGION_IS_SHARED(reg->flags)) {
 		/* Read only for both M and SU modes */
 		if (SBI_DOMAIN_MEMREGION_IS_SUR_MR(reg->flags))
 			pmp_flags = (PMP_L | PMP_R | PMP_W | PMP_X);
diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
index 2dca2699..d018619b 100644
--- a/lib/sbi/sbi_hart.c
+++ b/lib/sbi/sbi_hart.c
@@ -358,8 +358,6 @@ static int sbi_hart_smepmp_configure(struct sbi_scratch *scratch,
 		}
 
 		pmp_flags = sbi_domain_get_smepmp_flags(reg);
-		if (!pmp_flags)
-			return 0;
 
 		sbi_hart_smepmp_set(scratch, dom, reg, pmp_idx++, pmp_flags,
 				    pmp_log2gran, pmp_addr_max);
@@ -384,8 +382,6 @@ static int sbi_hart_smepmp_configure(struct sbi_scratch *scratch,
 		}
 
 		pmp_flags = sbi_domain_get_smepmp_flags(reg);
-		if (!pmp_flags)
-			return 0;
 
 		sbi_hart_smepmp_set(scratch, dom, reg, pmp_idx++, pmp_flags,
 				    pmp_log2gran, pmp_addr_max);
-- 
2.48.0