Re: [PATCH v3 1/2] target/riscv: use misa_mxl_max to populate isa string rather than TARGET_LONG_BITS

[Andrew Jones]

On Wed, Jan 10, 2024 at 10:25:36AM +0000, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley@microchip.com>
> 
> 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.
> 
> Reported-by: Andrew Jones <ajones@ventanamicro.com>
> Link: 
> https://lore.kernel.org/qemu-riscv/20240108-efa3f83dcd3997dc0af458d7@orel/
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> ---
> Perhaps this misa_mxl_max -> width conversion should exist as a macro?
> There's now 3 individual conversions of this type - two I added and one
> in the gdb code.

A macro is a good idea. I had to go look at Table 3.1 of the priv spec to
understand the 16 shift stuff.

> ---
>  target/riscv/cpu.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 8cbfc7e781..5b5da970f2 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -1860,7 +1860,9 @@ char *riscv_isa_string(RISCVCPU *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 = 16 << cpu->env.misa_mxl_max;
> +    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]);
> -- 
> 2.39.2
>

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>