From: Dave Hansen <dave.hansen@intel.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Feng Tang <feng.tang@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
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 10:18:38 -0700 [thread overview]
Message-ID: <98adc930-00e2-67c8-4ba3-fcb1af3aafd2@intel.com> (raw)
In-Reply-To: <20200902165216.GB21537@zn.tnic>
On 9/2/20 9:52 AM, Borislav Petkov wrote:
>> I was *really* hoping that we could eventually feed kcpuid and the
>> X86_FEATURE_* bits from the same source.
> But X86_FEATURE_* won't be all bits in all CPUID leafs - only the ones the
> kernel has enabled/use for/needs/...
>
> Also you have CPUID fields which are multi-bit and which cannot be
> X86_FEATURE_* things.
>
> So you need a place which has the whole CPUID space and X86_FEATURE_*
> simply cannot represent it all.
All good points.
Personally, I think I'd be OK if kcpuid _focused_ on single-bit values
only. Those are the vast majority of the things that we need from such
a tool. I don't think there's nearly as much demand for the topology
enumeration or TLB structure leaf parsing.
I also kinda doubt we can come up with a file format off the top of our
heads that can represent all the ways data is represented in the CPUID
space. Single bits, sure.
next prev parent reply other threads:[~2020-09-02 17:18 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-27 7:49 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 [this message]
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
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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