linux-kernel - Re: [PATCH v6 6/6] drivers/node: Show in sysfs node's crypto capabilities

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Date:   Mon, 7 Feb 2022 11:02:09 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Kees Cook <keescook@...omium.org>
Cc:     "Limonciello, Mario" <mario.limonciello@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Martin Fernandez <martin.fernandez@...ypsium.com>,
        linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
        platform-driver-x86@...r.kernel.org, linux-mm@...ck.org,
        tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
        x86@...nel.org, hpa@...or.com, ardb@...nel.org,
        dvhart@...radead.org, andy@...radead.org,
        gregkh@...uxfoundation.org, rafael@...nel.org, rppt@...nel.org,
        akpm@...ux-foundation.org, daniel.gutson@...ypsium.com,
        hughsient@...il.com, alex.bazhaniuk@...ypsium.com,
        alison.schofield@...el.com
Subject: Re: [PATCH v6 6/6] drivers/node: Show in sysfs node's crypto
 capabilities

On Sun, Feb 06, 2022 at 07:39:46PM -0800, Kees Cook wrote:
> Oh, this seems weird to me, as I'd expect it to show up since the CPU is
> _capable_ of it, even if it's not in use. (Am I really using avx512vl,
> e.g.?)

We're trying to put feature flags in /proc/cpuinfo which mean that the
kernel supports the feature - not every CPUID bit out there. For that
there's tools/arch/x86/kcpuid/kcpuid.c

Otherwise /proc/cpuinfo becomes a dumping ground for feature flags and
there's no shortage of those.

> But as you point out later, it does work that way for a lot of things
> and boot params. If this is the way things are supposed to be done,
> it looks like we should wire up "nx" vs "noexec=off" boot param to do

See here:

https://lore.kernel.org/r/20220127115626.14179-1-bp@alien8.de

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette