[RFC PATCH 01/12] lib: sbi_hart: detect RISC-V Worlds ISA extensions

[Yu-Chien Peter Lin]

Add detection for RISC-V Worlds ISA extensions (Smwid, Smlwid,
Smlwidlist, Smwiddeleg, Sswid) via ISA string detection and
CSR probes.

These feature flags enable subsequent patches to conditionally
configure World ID CSRs and print boot-time Worlds status.

Signed-off-by: Yu-Chien Peter Lin <peter.lin at sifive.com>
---
 include/sbi/riscv_encoding.h | 12 +++++++++
 include/sbi/sbi_hart.h       | 10 +++++++
 lib/sbi/sbi_hart.c           | 51 ++++++++++++++++++++++++++++++++++++
 3 files changed, 73 insertions(+)

diff --git a/include/sbi/riscv_encoding.h b/include/sbi/riscv_encoding.h
index ffe7666c..271820fd 100644
--- a/include/sbi/riscv_encoding.h
+++ b/include/sbi/riscv_encoding.h
@@ -400,6 +400,9 @@
 /* Supervisor Resource Management Configuration CSRs */
 #define CSR_SRMCFG			0x181
 
+/* Supervisor World-ID CSR (Sswid) */
+#define CSR_SLWID			0x190
+
 /* Machine-Level Control transfer records CSRs */
 #define CSR_MCTRCTL                     0x34e
 
@@ -520,6 +523,15 @@
 #define CSR_MTINST			0x34a
 #define CSR_MTVAL2			0x34b
 
+/* Machine World-ID CSRs (Smwid, Smlwid, Smlwidlist, Smwiddeleg) */
+#define CSR_MLWID			0x390
+#define CSR_MWID			0x391
+#define CSR_MWIDDELEG			0x748
+#define CSR_MLWIDLIST			0x749
+
+/* mwid lock bit */
+#define MWID_LOCK			(_UL(1) << (__riscv_xlen - 1))
+
 /* Machine Memory Protection */
 #define CSR_PMPCFG0			0x3a0
 #define CSR_PMPCFG1			0x3a1
diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
index 543393bb..2941809e 100644
--- a/include/sbi/sbi_hart.h
+++ b/include/sbi/sbi_hart.h
@@ -95,6 +95,16 @@ enum sbi_hart_extensions {
 	SBI_HART_EXT_F,
 	/** Hart has D extension */
 	SBI_HART_EXT_D,
+	/** Hart has Smwid extension */
+	SBI_HART_EXT_SMWID,
+	/** Hart has Smlwid extension */
+	SBI_HART_EXT_SMLWID,
+	/** Hart has Smlwidlist extension */
+	SBI_HART_EXT_SMLWIDLIST,
+	/** Hart has Smwiddeleg extension */
+	SBI_HART_EXT_SMWIDDELEG,
+	/** Hart has Sswid extension */
+	SBI_HART_EXT_SSWID,
 
 	/** Maximum index of Hart extension */
 	SBI_HART_EXT_MAX,
diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
index 21713816..0c584bfc 100644
--- a/lib/sbi/sbi_hart.c
+++ b/lib/sbi/sbi_hart.c
@@ -402,6 +402,11 @@ const struct sbi_hart_ext_data sbi_hart_ext[] = {
 	__SBI_HART_EXT_DATA(v, SBI_HART_EXT_V),
 	__SBI_HART_EXT_DATA(f, SBI_HART_EXT_F),
 	__SBI_HART_EXT_DATA(d, SBI_HART_EXT_D),
+	__SBI_HART_EXT_DATA(smwid, SBI_HART_EXT_SMWID),
+	__SBI_HART_EXT_DATA(smlwid, SBI_HART_EXT_SMLWID),
+	__SBI_HART_EXT_DATA(smlwidlist, SBI_HART_EXT_SMLWIDLIST),
+	__SBI_HART_EXT_DATA(smwiddeleg, SBI_HART_EXT_SMWIDDELEG),
+	__SBI_HART_EXT_DATA(sswid, SBI_HART_EXT_SSWID),
 };
 
 _Static_assert(SBI_HART_EXT_MAX == array_size(sbi_hart_ext),
@@ -689,6 +694,52 @@ __pmp_skip:
 	/* Detect if hart support sdtrig (debug triggers) */
 	__check_ext_csr(SBI_HART_PRIV_VER_UNKNOWN,
 			CSR_TSELECT, SBI_HART_EXT_SDTRIG);
+	/* Detect if hart supports Smwid (mwid CSR) */
+	__check_ext_csr(SBI_HART_PRIV_VER_UNKNOWN,
+			CSR_MWID, SBI_HART_EXT_SMWID);
+	/* Detect if hart supports Smlwid (mlwid CSR) */
+	__check_ext_csr(SBI_HART_PRIV_VER_UNKNOWN,
+			CSR_MLWID, SBI_HART_EXT_SMLWID);
+	/* Detect if hart supports Smlwidlist (mlwidlist CSR). */
+	__check_ext_csr(SBI_HART_PRIV_VER_UNKNOWN,
+			CSR_MLWIDLIST, SBI_HART_EXT_SMLWIDLIST);
+	/*
+	 * Detect if hart supports Smwiddeleg & Sswid.
+	 * Smwiddeleg requires Smlwid. Sswid requires Smwiddeleg.
+	 */
+	if (sbi_hart_has_extension(scratch, SBI_HART_EXT_SMLWID)) {
+		unsigned long old_mwiddeleg, new_mwiddeleg;
+
+		old_mwiddeleg = csr_read_allowed(CSR_MWIDDELEG, &trap);
+		if (trap.cause)
+			goto skip_smwiddeleg;
+
+		csr_write_allowed(CSR_MWIDDELEG, &trap, ~0UL);
+		if (trap.cause)
+			goto skip_smwiddeleg;
+
+		new_mwiddeleg = csr_read_allowed(CSR_MWIDDELEG, &trap);
+		if (trap.cause) {
+			csr_write(CSR_MWIDDELEG, old_mwiddeleg);
+			goto skip_smwiddeleg;
+		}
+
+		if (new_mwiddeleg) {
+			__sbi_hart_update_extension(hfeatures,
+						    SBI_HART_EXT_SMWIDDELEG, true);
+
+			csr_read_allowed(CSR_SLWID, &trap);
+			if (!trap.cause) {
+				__sbi_hart_update_extension(hfeatures,
+							    SBI_HART_EXT_SSWID, true);
+			}
+		}
+
+		csr_write(CSR_MWIDDELEG, old_mwiddeleg);
+
+skip_smwiddeleg:
+		;
+	}
 
 #undef __check_ext_csr
 
-- 
2.43.7