Re: [tip: x86/urgent] x86/CPU/AMD: Add RDSEED fix for Zen5

[Pavel Machek <pavel@ucw.cz>]

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Hi!

> > Add a fix glue which checks microcode revisions.
> > 
> >    [ bp: Add microcode revisions checking, rewrite. ]
> > 
> > Cc:stable@vger.kernel.org
> > Signed-off-by: Gregory Price<gourry@gourry.net>
> > Signed-off-by: Borislav Petkov (AMD)<bp@alien8.de>
> > Link:https://lore.kernel.org/r/20251018024010.4112396-1-gourry@gourry.net
> > ---
> >   arch/x86/kernel/cpu/amd.c | 10 ++++++++++
> >   1 file changed, 10 insertions(+)
> > 
> > diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> > index ccaa51c..bc29be6 100644
> > --- a/arch/x86/kernel/cpu/amd.c
> > +++ b/arch/x86/kernel/cpu/amd.c
> > @@ -1035,8 +1035,18 @@ static void init_amd_zen4(struct cpuinfo_x86 *c)
> >   	}
> >   }
> > +static const struct x86_cpu_id zen5_rdseed_microcode[] = {
> > +	ZEN_MODEL_STEP_UCODE(0x1a, 0x02, 0x1, 0x0b00215a),
> > +	ZEN_MODEL_STEP_UCODE(0x1a, 0x11, 0x0, 0x0b101054),
> > +};
> > +

> This fix seems to break quite a bunch of users in CachyOS. There has been
> now several users reporting that there system can not get properly into the
> graphical interface.
> 
> CachyOS is compiling the packages with -march=znver5 and the GCC compiler
> currently does pass RDSEED.

Besides other things, GCC should probably be fixed not to do that.

And this will be fun for both mainline and -stable: security bug or
broken boot, pick one :-(.

Best regards,
								Pavel
-- 
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