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Date: Tue, 3 May 2016 09:35:12 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Mike Travis <travis@sgi.com>
Cc: Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Len Brown <len.brown@intel.com>, Dimitri Sivanich <sivanich@sgi.com>,
        Russ Anderson <rja@sgi.com>, John Estabrook <estabrook@sgi.com>,
        Andrew Banman <abanman@sgi.com>, Nathan Zimmer <nzimmer@sgi.com>,
        x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 07/21] X86_64, UV: Disable Obsolete APIC ID fixup code
 used only on UV1
Message-ID: <20160503073512.GA13474@gmail.com>
References: <20160429215402.458042580@asylum.americas.sgi.com>
 <20160429215403.767900970@asylum.americas.sgi.com>
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* Mike Travis <travis@sgi.com> wrote:

> +config X86_UV1_SUPPORTED
> +	bool "SGI Ultraviolet Series 1 Supported"
> +	depends on X86_UV

So I still think it's much simpler if we simply eliminate this Kconfig 
complication and have it all compatible. AFAICS the runtime impact on newer 
systems comes down mostly to a single unlikely branch:

>  static unsigned int x2apic_get_apic_id(unsigned long x)
>  {
> -	unsigned int id;
> +	if (likely(!uv1_apic_driver))
> +		return x;

Thanks,

	Ingo