linux-kernel - Re: [PATCH v2 1/2] x86/cpufeature: Add facility to match microcode revisions

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Message-ID: <20181019234743.GA27951@tassilo.jf.intel.com>
Date:   Fri, 19 Oct 2018 16:47:43 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Andi Kleen <andi@...stfloor.org>, peterz@...radead.org,
        x86@...nel.org, eranian@...gle.com, kan.liang@...el.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] x86/cpufeature: Add facility to match microcode
 revisions

> > +	u32 min_ucode;
> > +};
> > +
> > +const struct x86_ucode_id *x86_match_ucode(const struct x86_ucode_id *match)
> 
> What's the point of returning the struct pointer? Shouldn't it be enough to
> make it return bool? Also the function name really should reflect that this
> checks whether the minimal required microcode revision is active.

This allows the user to find the table entry to tie something to it
(e.g. use the index to match some other table)

Same pattern as pci discovery etc. use.

Given the current caller doesn't need it, but we still follow standard
conventions.

> 
> > +{
> > +	struct cpuinfo_x86 *c = &boot_cpu_data;
> > +	const struct x86_ucode_id *m;
> > +
> > +	for (m = match; m->vendor | m->family | m->model; m++) {
> 
> VENDOR_INTEL = 0, so this check is obscure to begin with. Either you chose
> a explicit condition to put at the end of the table, e.g. vendor = U8_MAX
> or you hand in the array size to the function.

That would both be awkward. It's the same as match_cpu, and 0 terminators
are standard practice in practical all similar code. I removed
the or with the family.

-Andi