From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH v6 0/7] Add virtio-iommu driver Date: Wed, 12 Dec 2018 11:35:45 +0100 Message-ID: <20181212103545.GV16835@8bytes.org> References: <20181211182104.18241-1-jean-philippe.brucker@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20181211182104.18241-1-jean-philippe.brucker@arm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu To: Jean-Philippe Brucker Cc: virtio-dev@lists.oasis-open.org, kevin.tian@intel.com, lorenzo.pieralisi@arm.com, tnowicki@caviumnetworks.com, mst@redhat.com, marc.zyngier@arm.com, linux-pci@vger.kernel.org, jasowang@redhat.com, will.deacon@arm.com, robin.murphy@arm.com, virtualization@lists.linux-foundation.org, iommu@lists.linux-foundation.org, robh+dt@kernel.org, bhelgaas@google.com, frowand.list@gmail.com, kvmarm@lists.cs.columbia.edu, devicetree@vger.kernel.org List-Id: devicetree@vger.kernel.org Hi, to make progress on this, we should first agree on the protocol used between guest and host. I have a few points to discuss on the protocol first. On Tue, Dec 11, 2018 at 06:20:57PM +0000, Jean-Philippe Brucker wrote: > [1] Virtio-iommu specification v0.9, sources and pdf > git://linux-arm.org/virtio-iommu.git virtio-iommu/v0.9 > http://jpbrucker.net/virtio-iommu/spec/v0.9/virtio-iommu-v0.9.pdf Looking at this I wonder why it doesn't make the IOTLB visible to the guest. the UNMAP requests seem to require that the TLB is already flushed to make the unmap visible. I think that will cost significant performance for both, vfio and dma-iommu use-cases which both do (vfio at least to some degree), deferred flushing. I also wonder whether the protocol should implement a protocol version handshake and iommu-feature set queries. > [3] git://linux-arm.org/linux-jpb.git virtio-iommu/v0.9.1 > git://linux-arm.org/kvmtool-jpb.git virtio-iommu/v0.9 Unfortunatly gitweb seems to be broken on linux-arm.org. What is missing in this patch-set to make this work on x86? Regards, Joerg