From: peterz@infradead.org
To: Dave Hansen <dave.hansen@intel.com>
Cc: Feng Tang <feng.tang@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
Borislav Petkov <bp@alien8.de>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] tools/x86: add kcpuid tool to show raw CPU features
Date: Wed, 2 Sep 2020 18:59:50 +0200 [thread overview]
Message-ID: <20200902165950.GP1362448@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <6afa8f68-4e88-ade1-fbe9-7cc7a0d2e42c@intel.com>
On Wed, Sep 02, 2020 at 09:52:33AM -0700, Dave Hansen wrote:
> On 9/2/20 9:45 AM, peterz@infradead.org wrote:
> > On Thu, Aug 27, 2020 at 03:49:03PM +0800, Feng Tang wrote:
> >> End users frequently want to know what features their processor
> >> supports, independent of what the kernel supports.
> >>
> >> /proc/cpuinfo is great. It is omnipresent and since it is provided by
> >> the kernel it is always as up to date as the kernel. But, it can be
> >> ambiguous about processor features which can be disabled by the kernel
> >> at boot-time or compile-time.
> >
> > Let me once again suggest we use CPUID faulting to 'fix' this.
> >
> > We really should clear the CPUID bits when the kernel explicitly
> > disables things.
> >
> > https://lkml.kernel.org/r/1552431636-31511-18-git-send-email-fenghua.yu@intel.com
>
> Wouldn't we also have to turn on faulting for all the bits that are
> enumerated, but of which the kernel is unaware?
>
> Right now, a bit that we clearcpuid= and one about which the kernel is
> totally unaware look the same.
I mostly care about the things the kernel disables (and thus knows
about), the rest is a pass-through IIRC.
next prev parent reply other threads:[~2020-09-02 17:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-27 7:49 [RFC PATCH] tools/x86: add kcpuid tool to show raw CPU features Feng Tang
2020-09-02 15:40 ` Borislav Petkov
2020-09-02 16:25 ` Dave Hansen
2020-09-02 16:52 ` Borislav Petkov
2020-09-02 17:18 ` Dave Hansen
2020-09-02 18:19 ` Borislav Petkov
2020-09-03 7:17 ` Feng Tang
2020-09-02 16:45 ` peterz
2020-09-02 16:52 ` Dave Hansen
2020-09-02 16:59 ` peterz [this message]
2020-09-02 16:55 ` Borislav Petkov
2020-09-02 17:01 ` peterz
-- strict thread matches above, loose matches on Subject: below --
2020-07-21 2:00 Feng Tang
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