linux-kernel - Re: [PATCH v1 1/2] x86/cpufeature: Add facility to match microcode revisions

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Message-ID: <alpine.DEB.2.21.1810061809310.5454@nanos.tec.linutronix.de>
Date:   Sat, 6 Oct 2018 18:10:57 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andi Kleen <andi@...stfloor.org>
cc:     peterz@...radead.org, x86@...nel.org, linux-kernel@...r.kernel.org,
        eranian@...gle.com, kan.liang@...el.com, isaku.yamahata@...el.com,
        kvm@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v1 1/2] x86/cpufeature: Add facility to match microcode
 revisions

On Sat, 6 Oct 2018, Thomas Gleixner wrote:

> On Fri, 5 Oct 2018, Andi Kleen wrote:
> > +/*
> > + * Match specific microcodes or steppings.
> 
> What means microcodes or steppings? If you mean microcode revisions then
> please spell it out and use it all over the place. steppings is confusing
> at best as its associated to the CPU stepping.
> 
> > + *
> > + * vendor/family/model/stepping must be all set.
> > + * min_ucode/max_ucode/driver_data are optional and can be 0.
> > + */
> > +
> > +struct x86_ucode_id {
> > +	__u16 vendor;
> 
> __uXX are usually UAPI types. Please use the regular kernel uXX
> types instead.
> 
> > +	__u16 family;
> > +	__u16 model;
> > +	__u16 stepping;
> 
> Why u16? The corresponding members in cpuinfo_x86 are 8bit wide so why
> wasting memory for these tables?
> 
> > +	__u32 min_ucode;
> > +	__u32 max_ucode;
> > +	kernel_ulong_t driver_data;

Why do we need max_ucode and driver_data? I can't find an existing example
where this would be useful. If we need it later then it can be added
incrementaly.

Thanks,

	tglx