From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53213) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WDeGZ-0004DF-Az for qemu-devel@nongnu.org; Wed, 12 Feb 2014 13:10:41 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WDeGT-00028O-Ax for qemu-devel@nongnu.org; Wed, 12 Feb 2014 13:10:35 -0500 Received: from paradis.irqsave.net ([62.212.105.220]:49806) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WDeGT-000287-2C for qemu-devel@nongnu.org; Wed, 12 Feb 2014 13:10:29 -0500 Date: Wed, 12 Feb 2014 19:10:28 +0100 From: =?iso-8859-1?Q?Beno=EEt?= Canet Message-ID: <20140212181027.GB4225@irqsave.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] Guest IOMMU and Cisco usnic List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Alex Williamson Hi Alex, After the IRC conversation we had a few days ago I understood that guest = IOMMU was not implemented. I have a real use case for it: Cisco usnic allow to write MPI applications while driving the network car= d in userspace in order to optimize the latency. It's made for compute cluster= s. The typical cloud provider don't provide bare metal access but only vms o= n top of Cisco's hardware hence VFIO is using the IOMMU to passthrough the NIC = to the guest and no IOMMU is present in the guest. questions: Would writing a performing guest IOMMU implementation be possi= ble ? How complex this project looks for someone knowing IOMMUs issu= es ? The ideal implementation would forward the IOMMU work to the host hardwar= e for speed. I can devote time writing the feature if it's doable. Best regards Beno=EEt