From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH] VFIO driver: Non-privileged user level PCI drivers Date: Wed, 2 Jun 2010 13:09:58 +0300 Message-ID: <20100602100958.GB29023@redhat.com> References: <4C03A285.7060902@redhat.com> <20100531171007.GA6516@redhat.com> <4C04C085.1030107@redhat.com> <20100601095532.GA9178@redhat.com> <4C04E0E0.3070006@redhat.com> <20100601104651.GA9415@redhat.com> <4C050013.2020701@redhat.com> <20100602094527.GD964@8bytes.org> <4C062928.8040003@redhat.com> <20100602100404.GF964@8bytes.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Avi Kivity , Tom Lyon , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, chrisw@sous-sol.org, hjk@linutronix.de, gregkh@suse.de, aafabbri@cisco.com, scofeldm@cisco.com To: Joerg Roedel Return-path: Content-Disposition: inline In-Reply-To: <20100602100404.GF964@8bytes.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Wed, Jun 02, 2010 at 12:04:04PM +0200, Joerg Roedel wrote: > On Wed, Jun 02, 2010 at 12:49:28PM +0300, Avi Kivity wrote: > > On 06/02/2010 12:45 PM, Joerg Roedel wrote: > >> IOMMU mapped memory can not be swapped out because we can't do demand > >> paging on io-page-faults with current devices. We have to pin _all_ > >> userspace memory that is mapped into an IOMMU domain. > > > > vhost doesn't pin memory. > > > > What I proposed is to describe the memory map using an object (fd), and > > pass it around to clients that use it: kvm, vhost, vfio. That way you > > maintain the memory map in a central location and broadcast changes to > > clients. Only a vfio client would result in memory being pinned. > > Ah ok, so its only about the database which keeps the mapping > information. > > > It can still work, but the interface needs to be extended to include > > dirty bitmap logging. > > Thats hard to do. I am not sure about VT-d but the AMD IOMMU has no > dirty-bits in the page-table. And without demand-paging we can't really > tell what pages a device has written to. The only choice is to mark all > IOMMU-mapped pages dirty as long as they are mapped. > > Joerg Or mark them dirty when they are unmapped. -- MST