From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH v4] KVM: Introduce direct MSI message injection for in-kernel irqchips Date: Wed, 04 Apr 2012 11:38:44 +0200 Message-ID: <4F7C16A4.6070303@siemens.com> References: <4F734EB3.20500@siemens.com> <4F748AAD.2040103@siemens.com> <4F74B484.30607@siemens.com> <4F7B24EA.2070300@redhat.com> <4F7B29B5.6060703@siemens.com> <20120404083821.GB3003@redhat.com> <4F7C09E7.3020005@redhat.com> <20120404085359.GA3404@redhat.com> <4F7C12E3.3050702@siemens.com> <4F7C161D.3090909@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "Michael S. Tsirkin" , Marcelo Tosatti , kvm , Eric Northup To: Avi Kivity Return-path: Received: from david.siemens.de ([192.35.17.14]:20576 "EHLO david.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755930Ab2DDJis (ORCPT ); Wed, 4 Apr 2012 05:38:48 -0400 In-Reply-To: <4F7C161D.3090909@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 2012-04-04 11:36, Avi Kivity wrote: > On 04/04/2012 12:22 PM, Jan Kiszka wrote: >>> >>>>> Until we do have this fast path we can just fill this value with zeros, >>>>> so kernel patch (almost) does not need to change for this - >>>>> just the header. >>>> >>>> Partially implemented interfaces invite breakage. >>> >>> Hmm true. OK scrap this idea then, it's not clear >>> whether we are going to optimize this anyway. >>> >> >> Also, the problem is that keeping that ID in userspace requires an >> infrastructure like the MSIRoutingCache that I proposed originally. Not >> much won /wrt invasiveness there. > > Internal qemu refactorings are not a driver for kvm interface changes. No, but qemu demonstrates the applicability and handiness of the kernel interfaces. > >> So we should really do the routing >> optimization in the kernel - one day. > > No, we need to make a choice: > > explicit handles: array lookup, more expensive setup > no handles: hash loopup, more expensive, but no setup, and no artificial > limits ...and I think we should head for option 2. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux