linux-kernel - Re: [PATCH 0/3] Remove interrupt stack table usage from x86

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Message-ID: <20081228193046.GE496@one.firstfloor.org>
Date:	Sun, 28 Dec 2008 20:30:46 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Avi Kivity <avi@...hat.com>
Cc:	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	x86@...nel.org, linux-kernel <linux-kernel@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>
Subject: Re: [PATCH 0/3] Remove interrupt stack table usage from x86_64 kernel

> One fatal problem is enough -- I don't thing that patch can be made to 
> work.  Pity since it did clean up some stuff.

Not sure that was true anyways.

> I would like however to speed up kvm.  Here's a plan:
> 
> 1. Add per-cpu IDT

You don't need that, do you?  Just two sets.

> 2. When switching to the guest TR (and other state), switch off IST use 
> in the current IDT
> 3. When switching away from the kvm task, restore the IST entries
> 
> per-cpu IDT would cost around 4K per cpu.  I propose to make it 
> kconfigurable, and have kvm select it.

If anything please make it runtime switchable and disable it on Intel
CPUs.

-Andi
-- 
ak@...ux.intel.com
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