From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:60264) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UfTRZ-0003Xk-OL for qemu-devel@nongnu.org; Thu, 23 May 2013 07:12:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UfTRT-0003gz-HI for qemu-devel@nongnu.org; Thu, 23 May 2013 07:12:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:19360) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UfTRT-0003gn-7L for qemu-devel@nongnu.org; Thu, 23 May 2013 07:12:19 -0400 Date: Thu, 23 May 2013 14:12:38 +0300 From: "Michael S. Tsirkin" Message-ID: <20130523111238.GD17480@redhat.com> References: <1368059472-25071-1-git-send-email-david@gibson.dropbear.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1368059472-25071-1-git-send-email-david@gibson.dropbear.id.au> Subject: Re: [Qemu-devel] [0/8] Clean up PCI code to allow for multiple root buses List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson Cc: aliguori@us.ibm.com, qemu-devel@nongnu.org On Thu, May 09, 2013 at 10:31:04AM +1000, David Gibson wrote: > The current PCI subsystem has kind of half-hearted support for > multiple independent root buses - aka PCI domains - in the form of the > PCIHostBus structure and its domain field. However, it doesn't quite > work because pci_host_bus_register() is always called with a domain of > 0. > > Worse, though, the whole concept of numbered domains isn't general > enough. Many platforms can have independent root buses (usually on > wholly independent host bridges), but only x86 gives them a > hardware-significant domain number, essentially as a hack to allow all > the separate config spaces to be accessed via the same IO ports. > Linux guests on other platforms will show domain numbers in lspci, but > these are purely guest assigned, so qemu won't know about them. > > This patch series, therefore, removes the broken-as-is domain concept > from qemu, and replaces it with a different way of handling multiple > root buses, based on a host bridge class method to provide a > identifier for the root bus. This hook is designed in such a way as > to allow a single bridge object to support mutiple root buses with > future changes, which will allow future implementations of x86 north > bridges with multiple domains to be supported correctly, and in way > that matches the existing practice for all external interfaces. I agree with the direction this patchset takes. I sent some comments on the individual patches separately. Thanks! -- MST