linux-kernel - Re: [PATCH v2] x86, vt-d: enable x2apic opt out

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Message-ID: <1305636625.3146.119.camel@x201>
Date:	Tue, 17 May 2011 06:50:25 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	"Woodhouse, David" <david.woodhouse@...el.com>
Cc:	"Song, Youquan" <youquan.song@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"hpa@...or.com" <hpa@...or.com>,
	"hpa@...ux.intel.com" <hpa@...ux.intel.com>,
	"Kay, Allen M" <allen.m.kay@...el.com>,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	"Liu, Kent" <kent.liu@...el.com>,
	Youquan Song <youquan.song@...ux.intel.com>
Subject: Re: [PATCH v2] x86, vt-d: enable x2apic opt out

On Tue, 2011-05-17 at 10:49 +0100, Woodhouse, David wrote:
> On Mon, 2011-05-16 at 21:32 +0100, Alex Williamson wrote:
> > Just a guess, but the OEM probably hasn't updated their SMI handlers to
> > understand x2apic yet and won't before the product ships because some
> > other OS doesn't bother to use x2apic. 
> 
> Yay, crappy closed-source BIOS holds back the platform yet again.
> 
> >  We can still enable interrupt remapping w/o x2apic though, so I'm
> > curious what other irq injection tricks you're referring to.  Thanks,
> 
> http://www.invisiblethingslab.com/resources/2011/Software%20Attacks%20on%20Intel%20VT-d.pdf

Yep, I just read that, and while x2apic guarantees that we must turn on
the interrupt remapper and block compatibility format, lack of x2apic
doesn't preclude us from doing the same.  Right?  Thanks,

Alex

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