target/riscv: use misa_mxl_max to populate isa string rather than TARGET_LONG_BITS

A cpu may not have the same xlen as the compile time target, and
misa_mxl_max is the source of truth for what the hart supports.

The conversion from misa_mxl_max to xlen already has one user, so
introduce a helper and use that to populate the isa string.

Link: https://lore.kernel.org/qemu-riscv/20240108-efa3f83dcd3997dc0af458d7@orel/
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-ID: <20240124-swear-monthly-56c281f809a6@spud>
[ Changes by AF:
 - Convert to use RISCVCPUClass *mcc
]
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu.c

@@ -308,6 +308,11 @@ void riscv_cpu_set_misa_ext(CPURISCVState *env, uint32_t ext)
     env->misa_ext_mask = env->misa_ext = ext;
 }
 
+int riscv_cpu_max_xlen(RISCVCPUClass *mcc)
+{
+    return 16 << mcc->misa_mxl_max;
+}
+
 #ifndef CONFIG_USER_ONLY
 static uint8_t satp_mode_from_str(const char *satp_mode_str)
 {
@@ -2357,10 +2362,13 @@ static void riscv_isa_string_ext(RISCVCPU *cpu, char **isa_str,
 
 char *riscv_isa_string(RISCVCPU *cpu)
 {
+    RISCVCPUClass *mcc = RISCV_CPU_GET_CLASS(cpu);
     int i;
     const size_t maxlen = sizeof("rv128") + sizeof(riscv_single_letter_exts);
     char *isa_str = g_new(char, maxlen);
-    char *p = isa_str + snprintf(isa_str, maxlen, "rv%d", TARGET_LONG_BITS);
+    int xlen = riscv_cpu_max_xlen(mcc);
+    char *p = isa_str + snprintf(isa_str, maxlen, "rv%d", xlen);
+
     for (i = 0; i < sizeof(riscv_single_letter_exts) - 1; i++) {
         if (cpu->env.misa_ext & RV(riscv_single_letter_exts[i])) {
             *p++ = qemu_tolower(riscv_single_letter_exts[i]);

target/riscv/cpu.h

@@ -511,6 +511,7 @@ bool riscv_cpu_tlb_fill(CPUState *cs, vaddr address, int size,
                         MMUAccessType access_type, int mmu_idx,
                         bool probe, uintptr_t retaddr);
 char *riscv_isa_string(RISCVCPU *cpu);
+int riscv_cpu_max_xlen(RISCVCPUClass *mcc);
 bool riscv_cpu_option_set(const char *optname);
 
 #ifndef CONFIG_USER_ONLY

target/riscv/gdbstub.c

@@ -221,7 +221,7 @@ static int riscv_gen_dynamic_csr_xml(CPUState *cs, int base_reg)
     CPURISCVState *env = &cpu->env;
     GString *s = g_string_new(NULL);
     riscv_csr_predicate_fn predicate;
-    int bitsize = 16 << mcc->misa_mxl_max;
+    int bitsize = riscv_cpu_max_xlen(mcc);
     int i;
 
 #if !defined(CONFIG_USER_ONLY)