linux-kernel - Re: [PATCH v2] x86/entry/64: Do not use RDPID in paranoid entry to accomodate KVM

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Message-ID: <874kor57jm.fsf@nanos.tec.linutronix.de>
Date:   Tue, 25 Aug 2020 12:44:29 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Brian Gerst <brgerst@...il.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Chang Seok Bae <chang.seok.bae@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Sasha Levin <sashal@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH v2] x86/entry/64: Do not use RDPID in paranoid entry to accomodate KVM

On Fri, Aug 21 2020 at 11:35, Brian Gerst wrote:
> On Fri, Aug 21, 2020 at 10:22 AM Sean Christopherson
>> >  .macro GET_PERCPU_BASE reg:req
>> > -     ALTERNATIVE \
>> > -             "LOAD_CPU_AND_NODE_SEG_LIMIT \reg", \
>> > -             "RDPID  \reg", \
>>
>> This was the only user of the RDPID macro, I assume we want to yank that out
>> as well?
>
> No.  That one should be kept until the minimum binutils version is
> raised to one that supports the RDPID opcode.

The macro is unused and nothing in the kernel can use RDPID as we just
established.

Thanks,

        tglx