Improve PMP support

This implements a lot of missing functionality for PMPs.

* Support 64 PMPs as well as 0 and 16.
* Support setting PMP grain
* Return correct address bits on read (some read as 0 or 1 depending on the grain and match type)
* Unlock PMPs on reset
* Implement pmpcfg WARL legalisation

Co-authored-by: Ben Fletcher <benjamin.fletcher@codasip.com>

5 files changed, 42 insertions, 12 deletions

diff --git a/c_emulator/riscv_platform.c b/c_emulator/riscv_platform.c
index fbd63fa..253da35 100644
--- a/c_emulator/riscv_platform.c
+++ b/c_emulator/riscv_platform.c
@@ -47,6 +47,16 @@ bool sys_enable_vext(unit u)
   return rv_enable_vext;
 }
 
+uint64_t sys_pmp_count(unit u)
+{
+  return rv_pmp_count;
+}
+
+uint64_t sys_pmp_grain(unit u)
+{
+  return rv_pmp_grain;
+}
+
 bool sys_enable_writable_misa(unit u)
 {
   return rv_enable_writable_misa;
@@ -67,11 +77,6 @@ bool plat_mtval_has_illegal_inst_bits(unit u)
   return rv_mtval_has_illegal_inst_bits;
 }
 
-bool plat_enable_pmp(unit u)
-{
-  return rv_enable_pmp;
-}
-
 mach_bits plat_ram_base(unit u)
 {
   return rv_ram_base;
diff --git a/c_emulator/riscv_platform.h b/c_emulator/riscv_platform.h
index 4b6541f..38fac2f 100644
--- a/c_emulator/riscv_platform.h
+++ b/c_emulator/riscv_platform.h
@@ -9,10 +9,12 @@ bool sys_enable_writable_misa(unit);
 bool sys_enable_writable_fiom(unit);
 bool sys_enable_vext(unit);
 
+uint64_t sys_pmp_count(unit);
+uint64_t sys_pmp_grain(unit);
+
 bool plat_enable_dirty_update(unit);
 bool plat_enable_misaligned_access(unit);
 bool plat_mtval_has_illegal_inst_bits(unit);
-bool plat_enable_pmp(unit);
 
 mach_bits plat_ram_base(unit);
 mach_bits plat_ram_size(unit);
diff --git a/c_emulator/riscv_platform_impl.c b/c_emulator/riscv_platform_impl.c
index 15ff8ad..c2ae256 100644
--- a/c_emulator/riscv_platform_impl.c
+++ b/c_emulator/riscv_platform_impl.c
@@ -3,7 +3,9 @@
 #include <stdio.h>
 
 /* Settings of the platform implementation, with common defaults. */
-bool rv_enable_pmp = false;
+uint64_t rv_pmp_count = 0;
+uint64_t rv_pmp_grain = 0;
+
 bool rv_enable_zfinx = false;
 bool rv_enable_rvc = true;
 bool rv_enable_next = false;
diff --git a/c_emulator/riscv_platform_impl.h b/c_emulator/riscv_platform_impl.h
index e5c562a..e3e4a96 100644
--- a/c_emulator/riscv_platform_impl.h
+++ b/c_emulator/riscv_platform_impl.h
@@ -8,7 +8,9 @@
 
 #define DEFAULT_RSTVEC 0x00001000
 
-extern bool rv_enable_pmp;
+extern uint64_t rv_pmp_count;
+extern uint64_t rv_pmp_grain;
+
 extern bool rv_enable_zfinx;
 extern bool rv_enable_rvc;
 extern bool rv_enable_next;
diff --git a/c_emulator/riscv_sim.c b/c_emulator/riscv_sim.c
index 13d1653..f3c6343 100644
--- a/c_emulator/riscv_sim.c
+++ b/c_emulator/riscv_sim.c
@@ -51,6 +51,8 @@ const char *RV32ISA = "RV32IMAC";
 
 #define OPT_TRACE_OUTPUT 1000
 #define OPT_ENABLE_WRITABLE_FIOM 1001
+#define OPT_PMP_COUNT 1002
+#define OPT_PMP_GRAIN 1003
 
 static bool do_dump_dts = false;
 static bool do_show_times = false;
@@ -119,7 +121,8 @@ char *sailcov_file = NULL;
 static struct option options[] = {
     {"enable-dirty-update",         no_argument,       0, 'd'                     },
     {"enable-misaligned",           no_argument,       0, 'm'                     },
-    {"enable-pmp",                  no_argument,       0, 'P'                     },
+    {"pmp-count",                   required_argument, 0, OPT_PMP_COUNT           },
+    {"pmp-grain",                   required_argument, 0, OPT_PMP_GRAIN           },
     {"enable-next",                 no_argument,       0, 'N'                     },
     {"ram-size",                    required_argument, 0, 'z'                     },
     {"disable-compressed",          no_argument,       0, 'C'                     },
@@ -236,6 +239,8 @@ static int process_args(int argc, char **argv)
 {
   int c;
   uint64_t ram_size = 0;
+  uint64_t pmp_count = 0;
+  uint64_t pmp_grain = 0;
   while (true) {
     c = getopt_long(argc, argv,
                     "a"
@@ -281,9 +286,23 @@ static int process_args(int argc, char **argv)
       fprintf(stderr, "enabling misaligned access.\n");
       rv_enable_misaligned = true;
       break;
-    case 'P':
-      fprintf(stderr, "enabling PMP support.\n");
-      rv_enable_pmp = true;
+    case OPT_PMP_COUNT:
+      pmp_count = atol(optarg);
+      fprintf(stderr, "PMP count: %lld\n", pmp_count);
+      if (pmp_count != 0 && pmp_count != 16 && pmp_count != 64) {
+        fprintf(stderr, "invalid PMP count: must be 0, 16 or 64");
+        exit(1);
+      }
+      rv_pmp_count = pmp_count;
+      break;
+    case OPT_PMP_GRAIN:
+      pmp_grain = atol(optarg);
+      fprintf(stderr, "PMP grain: %lld\n", pmp_grain);
+      if (pmp_grain >= 64) {
+        fprintf(stderr, "invalid PMP grain: must less than 64");
+        exit(1);
+      }
+      rv_pmp_grain = pmp_grain;
       break;
     case 'C':
       fprintf(stderr, "disabling RVC compressed instructions.\n");