Re: [PATCH 3/3] util/cpuinfo-riscv: Use linux __riscv_hwprobe syscall

[Richard Henderson]

On 7/2/24 15:15, Daniel Henrique Barboza wrote:
> On 6/27/24 3:03 PM, Richard Henderson wrote:
> > With recent linux kernels, there is a syscall to probe for various
> > ISA extensions.  These bits were phased in over several kernel
> > releases, so we still require checks for symbol availability.
> >
> > Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> > ---
> >   meson.build          |  6 ++++++
> >   util/cpuinfo-riscv.c | 26 ++++++++++++++++++++++++++
> >   2 files changed, 32 insertions(+)
> >
> > diff --git a/meson.build b/meson.build
> > index 97e00d6f59..58afd0125d 100644
> > --- a/meson.build
> > +++ b/meson.build
> > @@ -2837,6 +2837,12 @@ have_cpuid_h = cc.links('''
> >     }''')
> >   config_host_data.set('CONFIG_CPUID_H', have_cpuid_h)
> > +# Don't bother to advertise asm/hwprobe.h for old versions that do
> > +# not contain RISCV_HWPROBE_EXT_ZBA.
> > +config_host_data.set('CONFIG_ASM_HWPROBE_H',
> > +                     cc.has_header_symbol('asm/hwprobe.h',
> > +                                          'RISCV_HWPROBE_EXT_ZBA'))
> > +
>
> FWIW I looked around Linux and I think we can snapshot hwprobe support by
> checking for RISCV_HWPROBE_KEY_IMA_EXT_0 (Linux commit 162e4df137c) if we
> ever need hwprobe for exts earlier than ZBA (C and V).

Sure.  It'll take some effort to use RVV for TCG vector operations.  :-)

> Checking for ZBA is fine for this patch though.
>
>
> Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>

Thanks.


r~