linux-kernel - Re: [PATCH v3 0/9] Parallel CPU bringup for x86

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Message-ID: <761c1552-0ca0-403b-3461-8426198180d0@amd.com>
Date:   Thu, 16 Dec 2021 10:27:40 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     David Woodhouse <dwmw2@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        rcu@...r.kernel.org, mimoja@...oja.de, hewenliang4@...wei.com,
        hushiyuan@...wei.com, luolongjun@...wei.com, hejingxian@...wei.com
Subject: Re: [PATCH v3 0/9] Parallel CPU bringup for x86_64

On 12/15/21 8:56 AM, David Woodhouse wrote:
> Doing the INIT/SIPI/SIPI in parallel for all APs and *then* waiting for
> them shaves about 80% off the AP bringup time on a 96-thread socket
> Skylake box (EC2 c5.metal) — from about 500ms to 100ms.
> 
> There are more wins to be had with further parallelisation, but this is
> the simple part.

I applied this series and began booting a regular non-SEV guest and hit a 
failure at 39 vCPUs. No panic or warning, just a reset and OVMF was 
executing again. I'll try to debug what's going, but not sure how quickly 
I'll arrive at anything.

Thanks,
Tom