riscv: S-mode extension parsing

There are now several Supervisor-mode extensions that have entered the
'ratified' status, so begin parsing and reporting a few of these.

Recognize the following extensions:
 - Sstc: stimecmp/vstimecmp CSR
 - Svnapot: NAPOT* translation contiguity
 - Svpbmt: page-based memory types
 - Svinval: fine-grained TLB invalidation instructions
 - Sscofpmf: performance counter overflow

*i.e. "naturally aligned power-of-2" page granularity

For now, provide globals for Sstc and Sscofpmf, as we will make use of
these in the near future.

Plus, update the copyright statement after my recent work on this file.

Reviewed by:	jhb
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D40240

sys/riscv/include/md_var.h

@@ -42,6 +42,10 @@ extern register_t marchid;
 extern register_t mimpid;
 extern u_int mmu_caps;
 
+/* Supervisor-mode extension support */
+extern bool has_sstc;
+extern bool has_sscofpmf;
+
 struct dumperinfo;
 struct minidumpstate;
 

sys/riscv/riscv/identcpu.c

@@ -1,6 +1,10 @@
 /*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
  * Copyright (c) 2015-2016 Ruslan Bukin <[email protected]>
  * All rights reserved.
+ * Copyright (c) 2022 Mitchell Horne <[email protected]>
+ * Copyright (c) 2023 The FreeBSD Foundation
  *
  * Portions of this software were developed by SRI International and the
  * University of Cambridge Computer Laboratory under DARPA/AFRL contract
@@ -10,6 +14,9 @@
  * Computer Laboratory as part of the CTSRD Project, with support from the
  * UK Higher Education Innovation Fund (HEIF).
  *
+ * Portions of this software were developed by Mitchell Horne
+ * <[email protected]> under sponsorship from the FreeBSD Foundation.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
@@ -67,11 +74,21 @@ register_t mimpid;	/* The implementation ID */
 
 u_int mmu_caps;
 
+/* Supervisor-mode extension support. */
+bool __read_frequently has_sstc;
+bool __read_frequently has_sscofpmf;
+
 struct cpu_desc {
 	const char	*cpu_mvendor_name;
 	const char	*cpu_march_name;
 	u_int		isa_extensions;		/* Single-letter extensions. */
 	u_int		mmu_caps;
+	u_int		smode_extensions;
+#define	 SV_SSTC	(1 << 0)
+#define	 SV_SVNAPOT	(1 << 1)
+#define	 SV_SVPBMT	(1 << 2)
+#define	 SV_SVINVAL	(1 << 3)
+#define	 SV_SSCOFPMF	(1 << 4)
 };
 
 struct cpu_desc cpu_desc[MAXCPU];
@@ -131,13 +148,29 @@ static const struct {
 #define	ISA_PREFIX_LEN		(sizeof(ISA_PREFIX) - 1)
 
 static __inline int
-parse_ext_s(struct cpu_desc *desc __unused, char *isa, int idx, int len)
+parse_ext_s(struct cpu_desc *desc, char *isa, int idx, int len)
 {
+#define	CHECK_S_EXT(str, flag)						\
+	do {								\
+		if (strncmp(&isa[idx], (str),				\
+		    MIN(strlen(str), len - idx)) == 0) {		\
+			desc->smode_extensions |= flag;			\
+			return (idx + strlen(str));			\
+		}							\
+	} while (0)
+
+	/* Check for known/supported extensions. */
+	CHECK_S_EXT("sstc",	SV_SSTC);
+	CHECK_S_EXT("svnapot",	SV_SVNAPOT);
+	CHECK_S_EXT("svpbmt",	SV_SVPBMT);
+	CHECK_S_EXT("svinval",	SV_SVINVAL);
+	CHECK_S_EXT("sscofpmf",	SV_SSCOFPMF);
+
+#undef CHECK_S_EXT
+
 	/*
 	 * Proceed to the next multi-letter extension or the end of the
 	 * string.
-	 *
-	 * TODO: parse these once we gain support
 	 */
 	while (isa[idx] != '_' && idx < len) {
 		idx++;
@@ -381,6 +414,10 @@ update_global_capabilities(u_int cpu, struct cpu_desc *desc)
 	 */
 	UPDATE_CAP(mmu_caps, desc->mmu_caps);
 
+	/* Supervisor-mode extension support. */
+	UPDATE_CAP(has_sstc, (desc->smode_extensions & SV_SSTC) != 0);
+	UPDATE_CAP(has_sscofpmf, (desc->smode_extensions & SV_SSCOFPMF) != 0);
+
 #undef UPDATE_CAP
 }
 
@@ -480,5 +517,15 @@ printcpuinfo(u_int cpu)
 		    "\15Mult/Div");
 	}
 
+	if (SHOULD_PRINT(smode_extensions)) {
+		printf("  S-mode Extensions: %#b\n", desc->smode_extensions,
+		    "\020"
+		    "\01Sstc"
+		    "\02Svnapot"
+		    "\03Svpbmt"
+		    "\04Svinval"
+		    "\05Sscofpmf");
+	}
+
 #undef SHOULD_PRINT
 }