Re: [Qemu-devel] [PATCH v2] RISC-V: Ignore the S and U letters when formatting ISA strings

[Alistair Francis <alistair23@gmail.com>]

On Tue, Aug 13, 2019 at 3:54 PM Palmer Dabbelt <palmer@sifive.com> wrote:
>
> The ISA strings we're providing from QEMU aren't actually legal RISC-V
> ISA strings, as both S and U cannot exist as single-letter extensions
> and must instead be multi-letter strings.  We're still using the ISA
> strings inside QEMU to track the availiable extensions, so this patch
> just strips out the S and U extensions when formatting ISA strings.
>
> This boots Linux on top of 4.1-rc3, which no longer has the U extension
> in /proc/cpuinfo.
>
> Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

It looks like you are using tabs in here, once they are removed:

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  target/riscv/cpu.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index f8d07bd20ad7..a67c54c738ba 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -501,7 +501,23 @@ char *riscv_isa_string(RISCVCPU *cpu)
>      char *p = isa_str + snprintf(isa_str, maxlen, "rv%d", TARGET_LONG_BITS);
>      for (i = 0; i < sizeof(riscv_exts); i++) {
>          if (cpu->env.misa & RV(riscv_exts[i])) {
> -            *p++ = qemu_tolower(riscv_exts[i]);
> +            char lower = qemu_tolower(riscv_exts[i]);
> +            switch (lower) {
> +            case 's':
> +            case 'u':
> +                /*
> +                * The 's' and 'u' letters shouldn't show up in ISA strings as
> +                * they're not extensions, but they should show up in MISA.
> +                * Since we use these letters interally as a pseudo ISA string
> +                * to set MISA it's easier to just strip them out when
> +                * formatting the ISA string.
> +                */
> +                break;
> +
> +            default:
> +                *p++ = lower;
> +                break;
> +            }
>          }
>      }
>      *p = '\0';
> --
> 2.21.0
>
>