Message-ID: <1338997720.2749.148.camel@twins>
Subject: Re: [PATCH 0/6] x86/cpu hotplug: Wake up offline CPU via mwait or
 nmi
From: Peter Zijlstra <peterz@infradead.org>
To: Arjan van de Ven <arjan@linux.intel.com>
Cc: paulmck@linux.vnet.ibm.com, Thomas Gleixner <tglx@linutronix.de>,
        "Luck, Tony" <tony.luck@intel.com>,
        "Yu, Fenghua" <fenghua.yu@intel.com>,
        Rusty Russell <rusty@rustcorp.com.au>, Ingo Molnar <mingo@elte.hu>,
        H Peter Anvin <hpa@zytor.com>,
        "Siddha, Suresh B" <suresh.b.siddha@intel.com>,
        "Mallick, Asit K" <asit.k.mallick@intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>,
        linux-pm <linux-pm@vger.kernel.org>,
        "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Date: Wed, 06 Jun 2012 17:48:40 +0200
In-Reply-To: <4FCF760A.7030501@linux.intel.com>
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On Wed, 2012-06-06 at 08:23 -0700, Arjan van de Ven wrote:
> btw TLB invalidation I think is a red herring in this discussion
> (other than "global PTEs" kind of kernel pte changes);
> at least on x86 this is not happening for a long time; if a CPU is
> really idle (which means the CPU internally flushes the tlbs anyway),
> Linux also switches to the kernel PTE set so there's no need for a flush
> later on. 

This is about isolation, not idle. If you share a mm across your
isolation barrier you get TLB invalidates, its unavoidable. The solution
is not sharing the mm -- which is a perfectly usable solution.
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