From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH v6 0/7] Add virtio-iommu driver Date: Wed, 12 Dec 2018 09:35:19 -0500 Message-ID: <20181212093413-mutt-send-email-mst@kernel.org> References: <20181211182104.18241-1-jean-philippe.brucker@arm.com> <20181212103545.GV16835@8bytes.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Content-Disposition: inline In-Reply-To: <20181212103545.GV16835@8bytes.org> To: Joerg Roedel Cc: Jean-Philippe Brucker , iommu@lists.linux-foundation.org, linux-pci@vger.kernel.org, devicetree@vger.kernel.org, virtualization@lists.linux-foundation.org, virtio-dev@lists.oasis-open.org, jasowang@redhat.com, robh+dt@kernel.org, mark.rutland@arm.com, bhelgaas@google.com, frowand.list@gmail.com, kvmarm@lists.cs.columbia.edu, eric.auger@redhat.com, tnowicki@caviumnetworks.com, kevin.tian@intel.com, marc.zyngier@arm.com, robin.murphy@arm.com, will.deacon@arm.com, lorenzo.pieralisi@arm.com, bharat.bhushan@nxp.com List-Id: devicetree@vger.kernel.org On Wed, Dec 12, 2018 at 11:35:45AM +0100, Joerg Roedel wrote: > 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 virtio has a builtin version handshake so devices don't need to. > 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? And I wonder about pcc too. > Regards, > > Joerg