From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v4] KVM: Introduce direct MSI message injection for in-kernel irqchips Date: Wed, 04 Apr 2012 12:36:29 +0300 Message-ID: <4F7C161D.3090909@redhat.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> 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: Jan Kiszka Return-path: Received: from mx1.redhat.com ([209.132.183.28]:61547 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753594Ab2DDJgf (ORCPT ); Wed, 4 Apr 2012 05:36:35 -0400 In-Reply-To: <4F7C12E3.3050702@siemens.com> Sender: kvm-owner@vger.kernel.org List-ID: 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. > 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 -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.