linux-kernel - Re: [PATCH 1/5] rcu,nohz: add state parameter to context_tracking_user

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Message-ID: <20150206182258.GH21905@lerouge>
Date:	Fri, 6 Feb 2015 19:23:00 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	kvm@...r.kernel.org, borntraeger@...ibm.com,
	linux-kernel@...r.kernel.org, mtosatti@...hat.com,
	mingo@...nel.orgm, ak@...ux.intel.com, oleg@...hat.com,
	masami.hiramatsu.pt@...achi.com, paulmck@...ux.vnet.ibm.com,
	lcapitulino@...hat.com, pbonzini@...hat.com
Subject: Re: [PATCH 1/5] rcu,nohz: add state parameter to
 context_tracking_user_enter/exit

On Fri, Feb 06, 2015 at 01:20:21PM -0500, Rik van Riel wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> On 02/06/2015 12:22 PM, Frederic Weisbecker wrote:
> > On Thu, Feb 05, 2015 at 03:23:48PM -0500, riel@...hat.com wrote:
> >> From: Rik van Riel <riel@...hat.com>
> >> 
> >> Add the expected ctx_state as a parameter to
> >> context_tracking_user_enter and context_tracking_user_exit,
> >> allowing the same functions to not just track kernel <> user
> >> space switching, but also kernel <> guest transitions.
> >> 
> >> Signed-off-by: Rik van Riel <riel@...hat.com>
> > 
> > You should consider using guest_enter() and guest_exit() instead.
> > These are context tracking APIs too but specifically for guest.
> 
> What do you mean instead?  KVM already uses those.
> 
> I just wanted to avoid duplicating the code...

I mean you can call rcu_user APIs directly from guest_enter/exit.
You don't really need to call the context_tracking_user functions
since guest_enter/guest_exit already handle the vtime accounting.

> 
> - -- 
> All rights reversed
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