Re: [PATCH] x86: Do not check FSRM in tst-cpu-features-cpuinfo

["H.J. Lu" <hjl.tools@gmail.com>]

On Mon, Feb 22, 2021 at 5:15 AM Florian Weimer <fweimer@redhat.com> wrote:
>
> * H. J. Lu:
>
> > On Mon, Feb 22, 2021 at 2:17 AM Florian Weimer via Libc-alpha
> > <libc-alpha@sourceware.org> wrote:
> >>
> >> Current kernels do not report this feature bit, so the test fails
> >> if the hardware supports it.
> >>
> >> According to
> >>
> >>   [PATCH v2] i386: Add the support for AMD EPYC 3rd generation processors
> >>   <https://lists.gnu.org/archive/html/qemu-devel/2021-02/msg03370.html>
> >>
> >> some AMD processors set this CPUID bit.
> >>
> >> ---
> >>  sysdeps/x86/tst-cpu-features-cpuinfo.c | 3 +++
> >>  1 file changed, 3 insertions(+)
> >>
> >> diff --git a/sysdeps/x86/tst-cpu-features-cpuinfo.c b/sysdeps/x86/tst-cpu-features-cpuinfo.c
> >> index 75e7eb9352..a6a873b59c 100644
> >> --- a/sysdeps/x86/tst-cpu-features-cpuinfo.c
> >> +++ b/sysdeps/x86/tst-cpu-features-cpuinfo.c
> >> @@ -153,7 +153,10 @@ do_test (int argc, char **argv)
> >>    fails += CHECK_PROC (fma4, FMA4);
> >>    fails += CHECK_PROC (fpu, FPU);
> >>    fails += CHECK_PROC (fsgsbase, FSGSBASE);
> >> +#if 0
> >> +  /* NB: /proc/cpuinfo doesn't report this feature.  */
> >>    fails += CHECK_PROC (fsrm, FSRM);
> >> +#endif
> >>    fails += CHECK_PROC (fxsr, FXSR);
> >>    fails += CHECK_PROC (gfni, GFNI);
> >>    fails += CHECK_PROC (hle, HLE);
> >>
> >
> > Since kernel does report it on Intel CPUs, please change it to
> >
> > /* NB: /proc/cpuinfo reports this feature on Intel CPUs.  */
> > if (cpu_features->basic.kind == arch_kind_intel)
> >
> > on top of
> >
> > https://sourceware.org/pipermail/libc-alpha/2021-January/122171.html
>
> Oh, it looks like that kernel support has only been added in Linux 5.6.
> Does this mean that tst-cpu-features-cpuinfo.c needs to check kernel
> versions?

Good idea.  BTW, we are checking GCC versions for __builtin_cpu_supports.


-- 
H.J.