linux-kernel - Re: [RFC PATCH] tools/x86: add kcpuid tool to show raw CPU features

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Date:   Thu, 3 Sep 2020 15:17:18 +0800
From:   Feng Tang <feng.tang@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] tools/x86: add kcpuid tool to show raw CPU features

On Wed, Sep 02, 2020 at 05:40:18PM +0200, Borislav Petkov wrote:
> On Thu, Aug 27, 2020 at 03:49:03PM +0800, Feng Tang wrote:
> > output of the tool
> > ------------------
> > 
> > 	CPUID leafs total: 28
> > 
> > 	cpu family	: 6
> > 	model		: 13
> > 	stepping	: 7
> 
> Yeah, this should dump model etc and those numbers should be in hex and
> additionally in dec if people prefer them.

Ok

> > 	CPU features
> > 	------------
> > 	 sse3
> > 	 pclmlqdq
> > 	 dtes64
> > 	 mwait
> > 	 ds_cpl
> > 	 vmx
> > 	 smx
> > 	 fpu
> > 	 ...
> 
> I guess that's good for grepping. With a lot of leafs, leaf output
> should probably be controlled by cmdline opts.

Will add input option for specific leafs or all.

> >  tools/arch/x86/tools/kcpuid/Makefile |  21 ++
> >  tools/arch/x86/tools/kcpuid/kcpuid.c | 422 +++++++++++++++++++++++++++++++++++
> >  2 files changed, 443 insertions(+)
> >  create mode 100644 tools/arch/x86/tools/kcpuid/Makefile
> >  create mode 100644 tools/arch/x86/tools/kcpuid/kcpuid.c
> 
> Let's drop the second "tools" from the path:
> 
> tools/arch/x86/kcpuid/Makefile
> tools/arch/x86/kcpuid/kcpuid.c

Will do.

> > +struct reg_01_a {
> > +	u32 stepping: 4;	/* bit 0 */
> > +	u32 model: 4;
> > +	u32 family: 4;
> > +	u32 type: 2;
> > +	u32 pad1: 2;
> > +	u32 model_ext: 4;	/* bit 16 */
> > +	u32 family_ext: 8;
> > +};
> 
> Yeah, instead of defining a separate struct for each leaf I think it
> would be smarter/better to have a text file in a machine parseable
> format which defines your leafs.
> 
> When you need to add a new leaf, you simply extend the text file and the
> tool parses it anew and has its all CPUID info uptodate. This way you
> won't even have to recompile it. Adding new CPUID leafs would be adding new
> lines to the file.
> 
> For example:
> 
> LEAF<num>,SUBLEAF<num>,[EAX,EBX,ECX,EDX]{[width]<Mnemonic>|<Long text>,...}
> 
> LEAF07,SUBLEAF00,EAX{[31:0]max_value|Max input value for supported subleafs}
> LEAF07,SUBLEAF00,EBX{[0]FSGSBASE|RDFSBASE/RDGSBASE/WRFSBASE/WRGSBASE if 1.,
> 		     [1]TSC_ADJUST|IA32_TSC_ADJUST MSR is supported if 1.,
> 		     [2]SGX|Supports Intel® Software Guard Extensions (Intel® SGX Extensions) if 1.,
> 		     ...
> }
> LEAF07,SUBLEAF00,ECX{[0]PREFETCHWT1|(Intel® Xeon PhiTM only.),
> 		     [1]AVX512_VBMI|,
> 		     ...
> 
> This is just a dumb attempt but I hope it comes across where I'm getting
> with this.

Will check this, and further study the different bits you, Peter and Dave
have mentioned in the discussion.

Thank you all for the review and suggestions!

- Feng