From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36241) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fijM3-0002Jg-Jo for qemu-devel@nongnu.org; Thu, 26 Jul 2018 12:43:08 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fijM0-0004XR-GT for qemu-devel@nongnu.org; Thu, 26 Jul 2018 12:43:07 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:36988 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 1fijM0-0004Uq-9j for qemu-devel@nongnu.org; Thu, 26 Jul 2018 12:43:04 -0400 Date: Thu, 26 Jul 2018 10:42:52 -0600 From: Alex Williamson Message-ID: <20180726104252.3d162f34@t450s.home> In-Reply-To: <20180726191315-mutt-send-email-mst@kernel.org> References: <1407239306.11199051.1530240887935.JavaMail.zimbra@redhat.com> <20180705194311-mutt-send-email-mst@kernel.org> <20180726145214.GD17777@stefanha-x1.localdomain> <488bdc8d-e36c-ad3e-f7b3-a45a78a99dda@gmail.com> <20180726191315-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] Question: SRIOV support over Win Hyper-V VM running in QEMU process on Linux host List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: Marcel Apfelbaum , Tal Attaly , Stefan Hajnoczi , Knut Omang , "qemu-devel@nongnu.org" , Elijah Shakkour On Thu, 26 Jul 2018 19:14:45 +0300 "Michael S. Tsirkin" wrote: > On Thu, Jul 26, 2018 at 06:51:13PM +0300, Marcel Apfelbaum wrote: > > Hi > > > > On 07/26/2018 05:52 PM, Stefan Hajnoczi wrote: > > > On Thu, Jul 12, 2018 at 07:33:14AM +0000, Elijah Shakkour wrote: > > > > Hey, > > > > > > > > Our team is adding a NIC functional emulation to QEMU. > > > > One of the features we are adding to this NIC is SRIOV. > > > > > > > > Here is the error message I get when checking SRIOV support of our emulated NIC on Win2016 server (the hyper-v VM). > > > > " > > > > SR-IOV cannot be used on this system as the PCI Express hardware does not support Access Control Services (ACS) at any root port. > > > > QEMU's emulated PCI Express Root Ports do not support ACS yet, however I am > > not sure ACS is a prerequisite > > for SR-IOV. ACS is certainly not a prerequisite for SR-IOV. > Looks like windows blocks dev assignment in nested VMs without it. > Thinking about it, doesn't vfio do the same by default? I think vfio has > a flag to override this though. IOMMU grouping in Linux takes isolation via ACS and device specific mechanisms into account, limiting the granularity with which a userspace driver can claim ownership of devices, but it doesn't actually prevent enabling SR-IOV on the endpoint. It just makes it less useful if your intention is to use SR-IOV for device assignment. The only overrides for this are out-of-tree. Thanks, Alex