Re: [PATCH v2 3/3] RISC-V: hwprobe: not treat KEY_CPUPERF_0 as bitmask

[Palmer Dabbelt]

On Wed, 29 May 2024 11:33:42 PDT (-0700), Evan Green wrote:
> On Thu, May 23, 2024 at 8:36 PM Yangyu Chen <cyy@xxxxxxxxxxxx> wrote:
> > Since the value in KEY_CPUPERF_0 is not bitmask, remove the wrong code
> > in hwprobe.h.
> >
> > Signed-off-by: Yangyu Chen <cyy@xxxxxxxxxxxx>
>
> I'd expect a Fixes tag, and ideally some discussion on the reasoning
> and ramifications of this change.
>
> I posted the other possible fix, declaring a new key, at [1], mostly
> so we could see the two options and discuss. I'm okay with either
> patch.

Just to close the loop here as the discussions are on other threads: 
after a bunch of discussions we're going with the new key version.  
Maybe it's a bit pedantic, but since hwprobe is such a fundamental 
compatibility interface we're just going to be super careful.

> -Evan
>
> [1] https://lore.kernel.org/lkml/20240529182649.2635123-1-evan@xxxxxxxxxxxx/T/#u
>
> > ---
> >  arch/riscv/include/asm/hwprobe.h | 1 -
> >  1 file changed, 1 deletion(-)
> >
> > diff --git a/arch/riscv/include/asm/hwprobe.h b/arch/riscv/include/asm/hwprobe.h
> > index 630507dff5ea..f24cad22bbe1 100644
> > --- a/arch/riscv/include/asm/hwprobe.h
> > +++ b/arch/riscv/include/asm/hwprobe.h
> > @@ -20,7 +20,6 @@ static inline bool hwprobe_key_is_bitmask(__s64 key)
> >         switch (key) {
> >         case RISCV_HWPROBE_KEY_BASE_BEHAVIOR:
> >         case RISCV_HWPROBE_KEY_IMA_EXT_0:
> > -       case RISCV_HWPROBE_KEY_CPUPERF_0:
> >                 return true;
> >         }
> >
> > --
> > 2.45.1