From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60181) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fLGrq-0001wg-K2 for qemu-devel@nongnu.org; Tue, 22 May 2018 19:38:59 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fLGrl-00081w-Nk for qemu-devel@nongnu.org; Tue, 22 May 2018 19:38:58 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:42256 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fLGrl-00081n-KL for qemu-devel@nongnu.org; Tue, 22 May 2018 19:38:53 -0400 Date: Wed, 23 May 2018 02:38:52 +0300 From: "Michael S. Tsirkin" Message-ID: <20180523005048-mutt-send-email-mst@kernel.org> References: <1526801333-30613-1-git-send-email-whois.zihan.yang@gmail.com> <1526801333-30613-4-git-send-email-whois.zihan.yang@gmail.com> <17a3765f-b835-2d45-e8b9-ffd4aff909f9@redhat.com> <20180522234410-mutt-send-email-mst@kernel.org> <20180522153659.2e33fbe0@w520.home> <20180523004236-mutt-send-email-mst@kernel.org> <20180522154741.3939d1e0@w520.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180522154741.3939d1e0@w520.home> Subject: Re: [Qemu-devel] [RFC 3/3] acpi-build: allocate mcfg for multiple host bridges List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alex Williamson Cc: Laszlo Ersek , Marcel Apfelbaum , Zihan Yang , qemu-devel@nongnu.org, Igor Mammedov , Eric Auger , Drew Jones , Wei Huang On Tue, May 22, 2018 at 03:47:41PM -0600, Alex Williamson wrote: > On Wed, 23 May 2018 00:44:22 +0300 > "Michael S. Tsirkin" wrote: > > > On Tue, May 22, 2018 at 03:36:59PM -0600, Alex Williamson wrote: > > > On Tue, 22 May 2018 23:58:30 +0300 > > > "Michael S. Tsirkin" wrote: > > > > > > > > It's not hard to think of a use-case where >256 devices > > > > are helpful, for example a nested virt scenario where > > > > each device is passed on to a different nested guest. > > > > > > > > But I think the main feature this is needed for is numa modeling. > > > > Guests seem to assume a numa node per PCI root, ergo we need more PCI > > > > roots. > > > > > > But even if we have NUMA affinity per PCI host bridge, a PCI host > > > bridge does not necessarily imply a new PCIe domain. > > > > What are you calling a PCIe domain? > > Domain/segment > > 0000:00:00.0 > ^^^^ This Right. So we can thinkably have PCIe root complexes share an ACPI segment. I don't see what this buys us by itself. > Isn't that the only reason we'd need a new MCFG section and the reason > we're limited to 256 buses? Thanks, > > Alex I don't know whether a single MCFG section can describe multiple roots. I think it would be certainly unusual. -- MST