linux-kernel - Re: [v4.17-rcx] Lost IBPB, IBRS_FW support for spectre

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Message-ID: <alpine.DEB.2.21.1805012025460.1596@nanos.tec.linutronix.de>
Date:   Tue, 1 May 2018 20:27:24 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Jörg Otte <jrg.otte@...il.com>
cc:     kirill.shutemov@...ux.intel.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [v4.17-rcx] Lost IBPB, IBRS_FW support for spectre_v2
 mitigation.

On Tue, 1 May 2018, Thomas Gleixner wrote:
> On Tue, 1 May 2018, Jörg Otte wrote:
> > 2018-04-30 21:53 GMT+02:00 Thomas Gleixner <tglx@...utronix.de>:
> > > --- a/arch/x86/kernel/cpu/common.c
> > > +++ b/arch/x86/kernel/cpu/common.c
> > > @@ -848,6 +848,11 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
> > >                 c->x86_power = edx;
> > >         }
> > >
> > > +       if (c->extended_cpuid_level >= 0x80000008) {
> > > +               cpuid(0x80000008, &eax, &ebx, &ecx, &edx);
> > > +               c->x86_capability[CPUID_8000_0008_EBX] = ebx;
> > > +       }
> > > +
> > >         if (c->extended_cpuid_level >= 0x8000000a)
> > >                 c->x86_capability[CPUID_8000_000A_EDX] = cpuid_edx(0x8000000a);
> > >
> > 
> > No, does not fix it.
> 
> Then I really have no idea how reverting the patch you pointed out would
> fix it.

Can you please carefully recheck:

1) rc3 with d94a155c59c9 reverted.

2) rc3 with the above patch applied.

If #1 works then #2 must work as well.

Thanks,

	tglx