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From:   Jim Mattson <jmattson@google.com>
Date:   Fri, 14 Feb 2020 09:43:13 -0800
Message-ID: <CALMp9eSdOz4NMHEM_J1V3PiyTsivPG3AJ-NX1CTvyxF_uJFaAQ@mail.gmail.com>
Subject: Re: [PATCH] kvm: x86: Print "disabled by bios" only once per host
To:     Erwan Velu <erwanaliasr1@gmail.com>
Cc:     Erwan Velu <e.velu@criteo.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Joerg Roedel <joro@8bytes.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        kvm list <kvm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Fri, Feb 14, 2020 at 6:33 AM Erwan Velu <erwanaliasr1@gmail.com> wrote:
>
> The current behavior is to print a "disabled by bios" message per CPU thread.
> As modern CPUs can have up to 64 cores, 128 on a dual socket, and turns this
> printk to be a pretty noisy by showing up to 256 times the same line in a row.
>
> This patch offer to only print the message once per host considering the BIOS will
> disabled the feature for all sockets/cores at once and not on a per core basis.

That's quite an assumption you're making. I guess I've seen more
broken BIOSes than you have. :-) Still, I would rather see the message
just once--perhaps with an additional warning if all logical
processors aren't in agreement.