From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [RFC][PATCH 12/45] msi: Introduce MSIRoutingCache Date: Mon, 17 Oct 2011 13:25:15 +0200 Message-ID: <4E9C109B.4070207@redhat.com> References: <4E9C0C42.60201@redhat.com> <4E9C0F5C.8000602@siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , "kvm@vger.kernel.org" , Alex Williamson , "Michael S. Tsirkin" , "qemu-devel@nongnu.org" To: Jan Kiszka Return-path: Received: from mx1.redhat.com ([209.132.183.28]:8791 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753242Ab1JQLZV (ORCPT ); Mon, 17 Oct 2011 07:25:21 -0400 In-Reply-To: <4E9C0F5C.8000602@siemens.com> Sender: kvm-owner@vger.kernel.org List-ID: On 10/17/2011 01:19 PM, Jan Kiszka wrote: > > IMO this needlessly leaks kvm information into core qemu. The cache > > should be completely hidden in kvm code. > > > > I think msi_deliver() can hide the use of the cache completely. For > > pre-registered events like kvm's irqfd, you can use something like > > > > qemu_irq qemu_msi_irq(MSIMessage msg) > > > > for non-kvm, it simply returns a qemu_irq that triggers a stl_phys(); > > for kvm, it allocates an irqfd and a permanent entry in the cache and > > returns a qemu_irq that triggers the irqfd. > > See my previously mail: you want to track the life-cycle of an MSI > source to avoid generating routes for identical sources. A messages is > not a source. Two identical messages can come from different sources. So > we need a separate data structure for that purpose. > Yes, I understand this now. Just to make sure I understand this completely: a hash table indexed by MSIMessage in kvm code would avoid this? You'd just allocate on demand when seeing a new MSIMessage and free on an LRU basis, avoiding pinned entries. I'm not advocating this (yet), just want to understand the tradeoffs. -- error compiling committee.c: too many arguments to function