linux-kernel - Re: [PATCH] x86, apic: Enable x2APIC physical when cpu

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Message-ID: <20130729170514.GB30371@linux-youquan.bj.intel.com>
Date:	Mon, 29 Jul 2013 13:05:14 -0400
From:	Youquan Song <youquan.song@...ux.intel.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Gleb Natapov <gleb@...hat.com>,
	Youquan Song <youquan.song@...el.com>,
	Sheng Yang <sheng@...ux.intel.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Youquan Song <youquan.song@...ux.intel.com>
Subject: Re: [PATCH] x86, apic: Enable x2APIC physical when cpu < 256 native

> 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

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