linux-kernel - Re: [PATCH] Ability to read the MKTME status from userspace

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Message-ID: <20200619161752.GG32683@zn.tnic>
Date:   Fri, 19 Jun 2020 18:17:52 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     Richard Hughes <hughsient@...il.com>,
        Daniel Gutson <daniel@...ypsium.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh@...nel.org>, Tony Luck <tony.luck@...el.com>,
        Rahul Tanwar <rahul.tanwar@...ux.intel.com>,
        Xiaoyao Li <xiaoyao.li@...el.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Ability to read the MKTME status from userspace

On Fri, Jun 19, 2020 at 08:48:47AM -0700, Andy Lutomirski wrote:
> Boris, it wouldn’t be totally crazy for cpuinfo to learn to
> distinguish between “your platform has this feature but Linux
> isn’t using it” and “your platform doesn’t have this feature
> in the first place”. And I suppose there’s this extra silly state
> “your platform has this feature, but your firmware didn’t enable
> it”. This would be a big job.

Well, I believe all the kernel can do is supply bits of information -
just like MSRs - and depending on the settings of those bits, userspace
can decide what the situation is. For example:

bit 0 - CPUID support
bit 1 - BIOS enabled
bit 2 - quirk applied
bit 3 - microcode fixes present
...

and so on.

It needs a proper definition though and userspace to say, yes, we want
that and that is useful for us.

Where it ends up is then beside the point - /proc/cpuinfo,
/sys/devices/system/cpu, whatever...

-- 
Regards/Gruss,
    Boris.

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