[PATCH v3 6/6] RISC-V: Do not use cpumask data structure for hartid bitmap

[Geert Uytterhoeven]

On Fri, Jan 28, 2022 at 9:39 AM Geert Uytterhoeven <geert at linux-m68k.org> wrote:
> On Fri, Jan 28, 2022 at 1:13 AM Atish Patra <atishp at atishpatra.org> wrote:
> > On Thu, Jan 27, 2022 at 12:48 AM Geert Uytterhoeven <geert at linux-m68k.org> wrote:
> >> What about shifting hmask and adjusting hbase if a hartid is
> >> lower than the current hbase?
> >
> > That will probably work for current systems but it will fail when we have hartid > 64.
> > The below logic as it assumes that the hartids are in order. We can have a situation
> > where a two consecutive cpuid belong to hartids that require two invocations of sbi call
> > because the number of harts exceeds BITS_PER_LONG.
>
> If the number of harts exceeds BITS_PER_LONG, you always need multiple
> calls, right?
>
> I think the below (gmail-whitespace-damaged diff) should work:
>
> --- a/arch/riscv/kernel/sbi.c
> +++ b/arch/riscv/kernel/sbi.c
> @@ -249,7 +249,7 @@ static void __sbi_set_timer_v02(uint64_t stime_value)
>
>  static int __sbi_send_ipi_v02(const struct cpumask *cpu_mask)
>  {
> -       unsigned long hartid, cpuid, hmask = 0, hbase = 0;
> +       unsigned long hartid, cpuid, hmask = 0, hbase = 0, htop = 0;
>         struct sbiret ret = {0};
>         int result;
>
> @@ -258,16 +258,27 @@ static int __sbi_send_ipi_v02(const struct
> cpumask *cpu_mask)
>
>         for_each_cpu(cpuid, cpu_mask) {
>                 hartid = cpuid_to_hartid_map(cpuid);
> -               if (hmask &&
> -                   (hartid < hbase || hartid >= hbase + BITS_PER_LONG)) {

Oops, I actually sent the diff against the simpler solution below,
not against the current code, but I guess you get the idea.
I can send a proper patch when agreed.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

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when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds