linux-kernel - RE: [PATCH v2] x86/cpufeature: Add feature dependency checks

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Message-ID: <SJ1PR11MB60836BD27B436E3E8B404AA2FC542@SJ1PR11MB6083.namprd11.prod.outlook.com>
Date: Wed, 30 Oct 2024 23:44:59 +0000
From: "Luck, Tony" <tony.luck@...el.com>
To: "Mehta, Sohil" <sohil.mehta@...el.com>, "x86@...nel.org" <x86@...nel.org>,
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>
CC: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H .
 Peter Anvin" <hpa@...or.com>, Uros Bizjak <ubizjak@...il.com>, Sandipan Das
	<sandipan.das@....com>, Sean Christopherson <seanjc@...gle.com>, "Peter
 Zijlstra" <peterz@...radead.org>, Vegard Nossum <vegard.nossum@...cle.com>,
	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, Nikolay Borisov
	<nik.borisov@...e.com>, Eric Biggers <ebiggers@...gle.com>, "Li, Xin3"
	<xin3.li@...el.com>, "Shishkin, Alexander" <alexander.shishkin@...el.com>,
	Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] x86/cpufeature: Add feature dependency checks

> +void filter_feature_dependencies(struct cpuinfo_x86 *c)
> +{
> +     const struct cpuid_dep *d;
> +
> +     for (d = cpuid_deps; d->feature; d++) {
> +             if (cpu_has(c, d->feature) && !cpu_has(c, d->depends))
> +                     do_clear_cpu_cap(c, d->feature);
> +     }
> +}

The dependency check found something very wrong. Should there be
a pr_warn() to give some clue that Linux papered over this problem?

-Tony