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From: Thomas Gleixner <tglx@linutronix.de>
To: "Jörg Otte" <jrg.otte@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Borislav Petkov <bp@alien8.de>
Subject: Re: [v4.17-rcx] Lost IBPB, IBRS_FW support for spectre_v2 mitigation.
Date: Wed, 2 May 2018 14:20:52 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1805021418550.1560@nanos.tec.linutronix.de> (raw)
In-Reply-To: <CADDKRnBn7rNN9UrwtYvNDPeJxqNQ-WHQVyHXAV7RwcVxX7jSDw@mail.gmail.com>

[-- Attachment #1: Type: text/plain, Size: 1649 bytes --]

On Wed, 2 May 2018, Jörg Otte wrote:
> 2018-05-02 11:02 GMT+02:00 Thomas Gleixner <tglx@linutronix.de>:
> > Ok, I think I know what's going wrong in that steaming pile of horrors of
> > CPUID detection. I need to analyze it down to the roots, but if you have
> > cycles, can you please test the patch below?
> >
> > It's a hack and even if it fixes the problem I'm going to do it differently.
> >
> > Thanks,
> >
> >         tglx
> >
> > 8<-------------------
> > --- 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);
> >
> > @@ -871,7 +876,6 @@ static void get_cpu_address_sizes(struct
> >
> >                 c->x86_virt_bits = (eax >> 8) & 0xff;
> >                 c->x86_phys_bits = eax & 0xff;
> > -               c->x86_capability[CPUID_8000_0008_EBX] = ebx;
> >         }
> >  #ifdef CONFIG_X86_32
> >         else if (cpu_has(c, X86_FEATURE_PAE) || cpu_has(c, X86_FEATURE_PSE36))
> >
> 
> OK, that patch works for me!

Thanks for confirming. Still need to find a way which is less fragile, but
that's probably too much of churn for rc4....

At least I know exactly what's happening, so I can write a better changelog.

Thanks for testing!

       tglx

  reply	other threads:[~2018-05-02 12:21 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-30 15:59 Jörg Otte
2018-04-30 19:53 ` Thomas Gleixner
2018-05-01  7:39   ` Jörg Otte
2018-05-01 12:59     ` Thomas Gleixner
2018-05-01 18:27       ` Thomas Gleixner
2018-05-01 23:07         ` Tim Chen
2018-05-01 20:14       ` Linus Torvalds
2018-05-02  7:43         ` Jörg Otte
2018-05-02  9:02           ` Thomas Gleixner
2018-05-02  9:25             ` Jörg Otte
2018-05-02 12:20               ` Thomas Gleixner [this message]
2018-05-04 16:18                 ` Borislav Petkov
2018-05-05  9:47                   ` Jörg Otte
2018-05-05  9:53                     ` Borislav Petkov
2018-05-02 14:48             ` [tip:x86/urgent] x86/cpu: Restore CPUID_8000_0008_EBX reload tip-bot for Thomas Gleixner
2018-05-02 18:08               ` Tim Chen

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