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From: Arvind Sankar <nivedita@alum.mit.edu>
To: Borislav Petkov <bp@alien8.de>
Cc: Feng Tang <feng.tang@intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Yazen Ghannam <yazen.ghannam@amd.com>,
	Wei Huang <wei.huang2@amd.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Dave Hansen <dave.hansen@intel.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v2] tools/x86: add kcpuid tool to show raw CPU features
Date: Tue, 22 Sep 2020 18:15:23 -0400	[thread overview]
Message-ID: <20200922221523.GA1185357@rani.riverdale.lan> (raw)
In-Reply-To: <20200922201024.GS22660@zn.tnic>

On Tue, Sep 22, 2020 at 10:10:24PM +0200, Borislav Petkov wrote:
> + AMD folks.
> 
> On Tue, Sep 22, 2020 at 01:27:50PM +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 could be
> > ambiguous about processor features which can be disabled by the kernel
> > at boot-time or compile-time.
> > 
> > There are some user space tools showing more raw features, but they are
> > not bound with kernel, and go with distros. Many end users are still
> > using old distros with new kernels (upgraded by themselves), and may
> > not upgrade the distros only to get a newer tool.
> > 
> > So here arise the need for a new tool, which
> >   * Shows raw cpu features got from running cpuid
> >   * Be easier to obtain updates for compared to existing userspace
> >     tooling (perhaps distributed like perf)
> >   * Inherits "modern" kernel development process, in contrast to some
> >     of the existing userspace cpuid tools which are still being developed
> >     without git and distributed in tarballs from non-https sites.
> >   * Can produce output consistent with /proc/cpuinfo to make comparison
> >     easier.

Rather than a tool, would additional file(s) in, say,
/sys/devices/system/cpu/cpu<n> be nicer? They could show the raw CPUID
features, one file per leaf or sub-leaf, maybe even along with whether
they were disabled at boot-time.

> >   * Be in-kernel, could leverage kernel enabling, and even
> >     theoretically consume arch/x86/boot/cpustr.h so it could pick up
> >     new features directly from one-line X86_FEATURE_* definitions.

That's arch/x86/include/asm/cpufeatures.h right -- cpustr.h is generated
from that. The table there already has comments which could be extracted
as the one-line description.


  reply	other threads:[~2020-09-22 22:15 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-22  5:27 [RFC PATCH v2] tools/x86: add kcpuid tool to show raw CPU features Feng Tang
2020-09-22 19:38 ` Dave Hansen
2020-09-25  7:22   ` Feng Tang
2020-09-25 17:27   ` Borislav Petkov
2020-09-22 20:10 ` Borislav Petkov
2020-09-22 22:15   ` Arvind Sankar [this message]
2020-09-23  2:45     ` Feng Tang
2020-09-25 17:16       ` Borislav Petkov
2020-09-25 19:48         ` Arvind Sankar
2020-09-25 20:17           ` Borislav Petkov
2020-09-25 20:40             ` Arvind Sankar
2020-09-25 20:57               ` Borislav Petkov
2020-09-25 17:24 ` Borislav Petkov
2020-09-25 17:26   ` Dave Hansen
2020-09-28  7:07   ` Feng Tang
2020-09-28  8:34     ` Borislav Petkov
2020-09-28  8:56       ` Feng Tang

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