Re: [PATCH] x86: Disable RTM on Skylake [BZ #27398]

[Florian Weimer <fw@deneb.enyo.de>]

* H. J. Lu:

> On Sat, Mar 27, 2021 at 12:15 PM Florian Weimer <fw@deneb.enyo.de> wrote:
>>
>> * H. J. Lu via Libc-alpha:
>>
>> > Disable RTM explicitly on Skylake since CPUID may incorrectly report RTM
>> > feature.
>> > ---
>> >  sysdeps/x86/cpu-features.c | 4 ++++
>> >  1 file changed, 4 insertions(+)
>> >
>> > diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
>> > index d7248cbb45..3641a48407 100644
>> > --- a/sysdeps/x86/cpu-features.c
>> > +++ b/sysdeps/x86/cpu-features.c
>> > @@ -518,6 +518,10 @@ init_cpu_features (struct cpu_features *cpu_features)
>> >                with stepping >= 4) to avoid TSX on kernels that weren't
>> >                updated with the latest microcode package (which disables
>> >                broken feature by default).  */
>> > +         case 0x8e:
>> > +         case 0x9e:
>> > +           /* Disable RTM explicitly on Skylake since CPUID may report
>> > +              RTM feature incorrectly [BZ #27398].  */
>> >             CPU_FEATURE_UNSET (cpu_features, RTM);
>> >             break;
>> >           }
>>
>> Won't this affect the server parts as well?  I'm not sure if that's
>> what our users want.
>
> No since Xeon has a different model number (0x55).

Hmm.  Xeon E3-1240 v6 has model number 158 (0x9e), too.