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Date: Mon, 29 Jul 2013 13:05:14 -0400
From: Youquan Song <youquan.song@linux.intel.com>
To: Yinghai Lu <yinghai@kernel.org>
Cc: Gleb Natapov <gleb@redhat.com>, Youquan Song <youquan.song@intel.com>,
        Sheng Yang <sheng@linux.intel.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "H. Peter Anvin" <hpa@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
        Youquan Song <youquan.song@linux.intel.com>
Subject: Re: [PATCH] x86, apic: Enable x2APIC physical when cpu < 256 native
Message-ID: <20130729170514.GB30371@linux-youquan.bj.intel.com>
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> Yes. It would be great, if Youquan can point out where is the intel doc
> about the change.
> 
> Also if the patch can move on,  hypervisor_x2apic_available() related
> declaration and define
> could be dropped.

Hi Yinghai,

Sorry I do not know the document change but I also do not find the
words/description/explanation that x2APIC physical mode also need interrupt
 remapping support when CPU < 256. Of course, X2APIC cluster mode must
has interrupt remapping support. 

I have tested many machines, both old and most recent machines and from
desktop to server, x2APIC physical mode works without interrupt
remapping when CPU < 256.

In theory and real test, I do not find any issue about the patch.

In order to make sure the patch without involving unexpected issues beyond
I can understand, I will confirm with our expert about it.

so please pend the patch going to mainline. If the patch can move on, I
think I will also provide other patch changing, like direct EOI.

Thanks
-Youquan