From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756232Ab2IUQRk (ORCPT ); Fri, 21 Sep 2012 12:17:40 -0400 Received: from smtp.citrix.com ([66.165.176.89]:51786 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752541Ab2IUQRj (ORCPT ); Fri, 21 Sep 2012 12:17:39 -0400 X-IronPort-AV: E=Sophos;i="4.80,463,1344211200"; d="scan'208";a="38746322" Message-ID: <505C9320.8030905@citrix.com> Date: Fri, 21 Sep 2012 17:17:36 +0100 From: David Vrabel User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.16) Gecko/20120428 Iceowl/1.0b1 Icedove/3.0.11 MIME-Version: 1.0 To: Konrad Rzeszutek Wilk CC: David Vrabel , Oliver Chick , "linux-kernel@vger.kernel.org" , Jan Beulich , "xen-devel@lists.xen.org" Subject: Re: [Xen-devel] [PATCH] Persistent grant maps for xen blk drivers References: <1348051887-21885-1-git-send-email-oliver.chick@citrix.com> <505AF126.2050806@citrix.com> <1348140637.24539.32.camel@oliverchick-Precision-WorkStation-T3400> <505B1EB9020000780009CA6E@nat28.tlf.novell.com> <505C5C54.4060100@citrix.com> <20120921142733.GB3389@phenom.dumpdata.com> In-Reply-To: <20120921142733.GB3389@phenom.dumpdata.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21/09/12 15:27, Konrad Rzeszutek Wilk wrote: > On Fri, Sep 21, 2012 at 01:23:48PM +0100, David Vrabel wrote: >> >> It's not just virtual space. blkback in pvops kernels allocates its >> pages from the balloon and if there aren't enough ballooned out pages it >> has to allocate real pages (releasing the MFN back to Xen). >> >> Classic kernels didn't need to do this as there was an API for allocate >> new "empty" struct page's that get mapped into kernel space. > > Can we ressurect/implement that in the new pvops? We could use the memory > hotplug mechanism to allocate "non-existent" memory. I don't see why not. Provided the limitations are documented I wouldn't make merging the persistent grant stuff dependent on it. David