linux-kernel - Re: [PATCH v3 04/12] Add "handle page fault" PV helper.

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Message-ID: <20100117151218.GJ31692@redhat.com>
Date:	Sun, 17 Jan 2010 17:12:18 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	kvm@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, avi@...hat.com, mingo@...e.hu,
	tglx@...utronix.de, hpa@...or.com, riel@...hat.com,
	cl@...ux-foundation.org
Subject: Re: [PATCH v3 04/12] Add "handle page fault" PV helper.

On Sun, Jan 17, 2010 at 04:09:40PM +0100, Peter Zijlstra wrote:
> On Sun, 2010-01-17 at 16:44 +0200, Gleb Natapov wrote:
> > On Thu, Jan 14, 2010 at 06:31:07PM +0100, Peter Zijlstra wrote:
> > > On Tue, 2010-01-05 at 16:12 +0200, Gleb Natapov wrote:
> > > > Allow paravirtualized guest to do special handling for some page faults.
> > > > 
> > > > The patch adds one 'if' to do_page_fault() function. The call is patched
> > > > out when running on physical HW. I ran kernbech on the kernel with and
> > > > without that additional 'if' and result were rawly the same:
> > > 
> > > So why not program a different handler address for the #PF/#GP faults
> > > and avoid the if all together?
> > I would gladly use fault vector reserved by x86 architecture, but I am
> > not sure Intel will be happy about it.
> 
> Whatever are we doing to end up in do_page_fault() as it stands? Surely
> we can tell the CPU to go elsewhere to handle faults?
> 
> Isn't that as simple as calling set_intr_gate(14, my_page_fault)
> somewhere on the cpuinit instead of the regular page_fault handler?
> 
Hmm, good idea. I'll look into that. Thanks.

--
			Gleb.
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