Message-ID: <5ba476f3-e0ac-d630-ce1d-18ab9885496f@linux.intel.com>
Date:   Sat, 4 Feb 2023 10:18:55 -0800
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Subject: Re: [PATCH v6 07/11] x86/smpboot: Disable parallel boot for AMD CPUs
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To:     David Woodhouse <dwmw2@infradead.org>,
        Kim Phillips <kim.phillips@amd.com>,
        Usama Arif <usama.arif@bytedance.com>, tglx@linutronix.de
Cc:     mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
        hpa@zytor.com, x86@kernel.org, pbonzini@redhat.com,
        paulmck@kernel.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, rcu@vger.kernel.org, mimoja@mimoja.de,
        hewenliang4@huawei.com, thomas.lendacky@amd.com, seanjc@google.com,
        pmenzel@molgen.mpg.de, fam.zheng@bytedance.com,
        punit.agrawal@bytedance.com, simon.evans@bytedance.com,
        liangma@liangbit.com, Mario Limonciello <Mario.Limonciello@amd.com>
References: <20230202215625.3248306-1-usama.arif@bytedance.com>
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 <b3d9fbbf-e760-5d1d-9182-44c144abd1bf@amd.com>
 <d3ec562fd2e03c3aef9534f64915a14a8cb89ae1.camel@infradead.org>
From:   Arjan van de Ven <arjan@linux.intel.com>
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> 
> However...
> 
> Even though we *can* support non-X2APIC processors, we *might* want to
> play it safe and not go back that far; only enabling parallel bringup
> on machines with X2APIC which roughly correlates with "lots of CPUs"
> since that's where the benefit is.

I think that this is the right approach, at least on the initial patch series.
KISS principle; do all the easy-but-important cases first, get it stable and working
and in later series/kernels the range can be expanded.... if it matters.


> 
> 
>