From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [patch 01/13] x86/mm: get_user_pages_fast_atomic Date: Sun, 07 Sep 2008 11:42:18 +0300 Message-ID: <48C393EA.2080707@qumranet.com> References: <20080906184822.560099087@localhost.localdomain> <20080906192430.514756352@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Marcelo Tosatti Return-path: Received: from il.qumranet.com ([212.179.150.194]:53828 "EHLO il.qumranet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751049AbYIGImU (ORCPT ); Sun, 7 Sep 2008 04:42:20 -0400 In-Reply-To: <20080906192430.514756352@localhost.localdomain> Sender: kvm-owner@vger.kernel.org List-ID: Marcelo Tosatti wrote: > From: Nick Piggin > > Provide a lockless pagetable walk function without fallback to mmap_sem > on error. > I would like to avoid this if possible. Not only is this a change to the core (with backporting headaches), if we resync in atomic context this can mean a long time spent with preemption disabled. We might get around the need by dropping the lock when we resync, fetch the gfns without the lock, and after reacquiring it check whether we can proceed or whether we need to abort and let the guest retry. We can probably proceed unless one of two things have happened: an mmu page was zapped, or out page was oos'ed while we were resyncing it. -- error compiling committee.c: too many arguments to function