From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Mq73l-00012F-Cm for qemu-devel@nongnu.org; Tue, 22 Sep 2009 11:13:41 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1Mq73f-000123-Vl for qemu-devel@nongnu.org; Tue, 22 Sep 2009 11:13:40 -0400 Received: from [199.232.76.173] (port=60932 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Mq73f-000120-Rk for qemu-devel@nongnu.org; Tue, 22 Sep 2009 11:13:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48342) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1Mq73f-0007t4-B9 for qemu-devel@nongnu.org; Tue, 22 Sep 2009 11:13:35 -0400 Message-ID: <4AB8E88C.4040103@redhat.com> Date: Tue, 22 Sep 2009 11:09:00 -0400 From: john cooper MIME-Version: 1.0 Subject: Re: [Qemu-devel] Re: [PATCH] qemu: make virtio-blk PCI compliant by default References: <20090907181436.GA8538@redhat.com> <4AA60A58.4090703@redhat.com> <20090908075831.GA9875@redhat.com> <200909212039.01126.rusty@rustcorp.com.au> <4AB7A01A.3000206@redhat.com> <4AB8992B.7070709@redhat.com> <4AB8DD53.7070806@redhat.com> <4AB8DECA.3090908@redhat.com> In-Reply-To: <4AB8DECA.3090908@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Avi Kivity Cc: john.cooper@redhat.com, Rusty Russell , "Michael S. Tsirkin" , qemu-devel@nongnu.org, jens.axboe@oracle.com Avi Kivity wrote: > On 09/22/2009 05:21 PM, john cooper wrote: >>> Can we just read this page as a virtqueue command instead of having it >>> mapped permanently? >>> >> Probably although I hadn't looked specifically >> at doing so. Mapping the data via an unused >> pci bar is pretty trivial and seemed minimally >> intrusive to the existing driver. >> > > We'll run out of bars if we expend them like that. Agreed. However my motivation here was to use a single additional bar specifically to compensate for the PCI spec imposed 256 byte size limitation of the config space mapping. As we're defining the content/size of this area, future use to accommodate additional data should be unrestricted. If using an additional bar is still a concern I can certainly have a look at accomplishing the same via virtqueue scaffolding. -john -- john.cooper@redhat.com