Re: [PATCH] x86/cpu/centaur: Disable X86_FEATURE_FSGSBASE on Zhaoxin C4600

[Christian Ludloff]

much appreciated – many thanks!

--
C.

On Wed, Mar 11, 2026 at 7:19 PM Tony W Wang-oc <TonyWWang-oc@xxxxxxxxxxx> wrote:
>
>
>
> On 2026/3/6 04:26, Christian Ludloff wrote:
> >
> >
> > Tony,
> >
> > can you confirm whether F=6 M=1F is affected or not?
> > (Supposedly that's ZX-D... but the F in the model does
> > make me wonder/ask.)
> >
> This bug existed only in certain early ucode revisions of the ZX-C/ZX-C+
> series CPUs, and is not present in the ZX-D.
>
> > Presumably the 6FE and 10690 microcodes which are
> > out in the wild do not fix the bug, correct?
> >
> > 000006fe_00000000_20110809_8f396f73
> > 000006fe_00000000_20110809_8f397072
> > 000006fe_00000001_20160525_7214d1e1
> > 000006fe_00000001_20170109_25646399
> > 000006fe_00000001_20180726_6e07329b
> > 000006fe_00000001_20180726_6e1e984b
> >
> > 00010690_00000000_20110809_259878a5
> > 00010690_00000001_20160525_3c34fc1a
> > 00010690_00000001_20170109_a8b24dc2
> > 00010690_00000001_20180726_0c55f25d
> > 00010690_00000001_20180726_41faefde
> >
> No, The four patches with the display date of 20180726 should not have
> this bug.
>
> > As for making the code conditional for Centaur/Zhaoxin,
> > stepping E seems to be when FSGSBASE arrived – and
> > while there are CPUID dumps for 6FE that say VIA Eden
> > it is possible that they too have the bug.
> >
> Sorry, VIA Eden is too old, we haven't been able to find actual hardware
> to confirm this.
>
> > As for making the code conditional for Zhaoxin models in
> > the string, that would require more than just C4600 – the
> > collection of known dumps includes others.
> >
> Yes, ZX-C/ZX-C+ series CPUs have other strings.
>
> Sincerely!
> TonyWWang-oc
> > --
> > C.