target/riscv: Make PMP granularity configurable

Previously, the PMP granularity in qemu always used a minimum
granularity of 4 bytes, this patch add pmp-granularity to allow
platforms to configure the value.

A new CPU parameter pmp-granularity has been introduced to the QEMU
command line. For example:

        -cpu rv64, g=true, c=true, pmp=true, pmp-granularity=1024

If no specific value is provided, the default value is 4 bytes.

Signed-off-by: Jay Chang <jay.chang@sifive.com>
Reviewed-by: Frank Chang <frank.chang@sifive.com>
Reviewed-by: Jim Shu <jim.shu@sifive.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20251022024141.42178-2-jay.chang@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu.c

@@ -1121,6 +1121,7 @@ static void riscv_cpu_init(Object *obj)
     cpu->cfg.cbop_blocksize = 64;
     cpu->cfg.cboz_blocksize = 64;
     cpu->cfg.pmp_regions = 16;
+    cpu->cfg.pmp_granularity = MIN_RISCV_PMP_GRANULARITY;
     cpu->env.vext_ver = VEXT_VERSION_1_00_0;
     cpu->cfg.max_satp_mode = -1;
 
@@ -1606,6 +1607,43 @@ static const PropertyInfo prop_num_pmp_regions = {
     .set = prop_num_pmp_regions_set,
 };
 
+static void prop_pmp_granularity_set(Object *obj, Visitor *v, const char *name,
+                                     void *opaque, Error **errp)
+{
+    RISCVCPU *cpu = RISCV_CPU(obj);
+    uint32_t value;
+
+    visit_type_uint32(v, name, &value, errp);
+
+    if ((value < MIN_RISCV_PMP_GRANULARITY) && (value & (value - 1))) {
+        error_setg(errp, "PMP granularity must be a power of 2 and at least %d",
+                   MIN_RISCV_PMP_GRANULARITY);
+        return;
+    }
+
+    if (cpu->cfg.pmp_granularity != value && riscv_cpu_is_vendor(obj)) {
+        cpu_set_prop_err(cpu, name, errp);
+        return;
+    }
+
+    cpu_option_add_user_setting(name, value);
+    cpu->cfg.pmp_granularity = value;
+}
+
+static void prop_pmp_granularity_get(Object *obj, Visitor *v, const char *name,
+                                     void *opaque, Error **errp)
+{
+    uint32_t value = RISCV_CPU(obj)->cfg.pmp_granularity;
+
+    visit_type_uint32(v, name, &value, errp);
+}
+
+static const PropertyInfo prop_pmp_granularity = {
+    .description = "pmp-granularity",
+    .get = prop_pmp_granularity_get,
+    .set = prop_pmp_granularity_set,
+};
+
 static int priv_spec_from_str(const char *priv_spec_str)
 {
     int priv_version = -1;
@@ -2606,6 +2644,7 @@ static const Property riscv_cpu_properties[] = {
     {.name = "mmu", .info = &prop_mmu},
     {.name = "pmp", .info = &prop_pmp},
     {.name = "num-pmp-regions", .info = &prop_num_pmp_regions},
+    {.name = "pmp-granularity", .info = &prop_pmp_granularity},
 
     {.name = "priv_spec", .info = &prop_priv_spec},
     {.name = "vext_spec", .info = &prop_vext_spec},

target/riscv/cpu.h

@@ -176,6 +176,7 @@ extern RISCVCPUImpliedExtsRule *riscv_multi_ext_implied_rules[];
 
 #define MAX_RISCV_PMPS (64)
 #define OLD_MAX_RISCV_PMPS (16)
+#define MIN_RISCV_PMP_GRANULARITY 4
 
 #if !defined(CONFIG_USER_ONLY)
 #include "pmp.h"

target/riscv/cpu_cfg_fields.h.inc

@@ -166,6 +166,7 @@ TYPED_FIELD(uint16_t, cbom_blocksize, 0)
 TYPED_FIELD(uint16_t, cbop_blocksize, 0)
 TYPED_FIELD(uint16_t, cboz_blocksize, 0)
 TYPED_FIELD(uint8_t,  pmp_regions, 0)
+TYPED_FIELD(uint32_t, pmp_granularity, 0)
 
 TYPED_FIELD(int8_t, max_satp_mode, -1)