linux-kernel - Re: [PATCH] x86/entry/64: Disallow RDPID in paranoid entry if KVM is enabled

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Message-ID: <20200821074400.GA12181@zn.tnic>
Date:   Fri, 21 Aug 2020 09:44:00 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     peterz@...radead.org
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...el.com>,
        Chang Seok Bae <chang.seok.bae@...el.com>,
        Sasha Levin <sashal@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [PATCH] x86/entry/64: Disallow RDPID in paranoid entry if KVM is
 enabled

On Fri, Aug 21, 2020 at 09:24:14AM +0200, peterz@...radead.org wrote:
> With distro configs that's going to be a guaranteed no_rdpid. Also with
> a grand total of 0 performance numbers that RDPID is even worth it, I'd
> suggest to just unconditionally remove that thing. Simpler code
> all-around.

I was just about to say the same thing - all this dancing around just to
keep RDPID better be backed by numbers, otherwise just remove the damn
thing in that path and use LSL and be done with it.

-- 
Regards/Gruss,
    Boris.

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