From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrea Arcangeli Subject: Re: [PATCH] kvm-userland mm count skew Date: Tue, 22 Jan 2008 15:25:26 +0100 Message-ID: <20080122142525.GB7331@v2.random> References: <20080121124455.GI6970@v2.random> <4795F26E.9090807@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Avi Kivity Return-path: Content-Disposition: inline In-Reply-To: <4795F26E.9090807-atKUWr5tajBWk0Htik3J/w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org On Tue, Jan 22, 2008 at 03:41:02PM +0200, Avi Kivity wrote: > Andrea Arcangeli wrote: >> I still can't see how it could be possibly make a difference for the >> mm_count if the kvm module is compiled inside the kernel or as an >> external module, the reference counting there hasn't changed since >> ages. The mmdrop fires only in the first overflow so even if I'm right >> it probably wasn't much destabilizing to go negative given it happened >> at mm destruction time. >> >> > > It's this bit: Ok. But the atomic_inc removal isn't conditional to < 2.6.25, so it still doesn't look good to me. it would look better if we would unconditionally define mmdrop to nop in the external module compile. The other problem is that I don't see why atomic_inc/mmdrop are needed at all if the external module is safe, so why don't we drop them? In ->release->kvm_destroy_vm it seems the kvm->mm is never used anyway. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/