From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tom Lyon Subject: Re: [PATCH V2] VFIO driver: Non-privileged user level PCI drivers Date: Wed, 30 Jun 2010 21:30:38 -0700 Message-ID: <201006302130.38987.pugs@lyon-about.com> References: <4c0eb470.1HMjondO00NIvFM6%pugs@cisco.com> <1277957783.10112.15.camel@x201> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: randy.dunlap@oracle.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, chrisw@sous-sol.org, joro@8bytes.org, hjk@linutronix.de, mst@redhat.com, avi@redhat.com, gregkh@suse.de, aafabbri@cisco.com, scofeldm@cisco.com To: Alex Williamson Return-path: Received: from sj-iport-6.cisco.com ([171.71.176.117]:9948 "EHLO sj-iport-6.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750718Ab0GAEeR (ORCPT ); Thu, 1 Jul 2010 00:34:17 -0400 In-Reply-To: <1277957783.10112.15.camel@x201> Content-Disposition: inline Sender: kvm-owner@vger.kernel.org List-ID: On Wednesday 30 June 2010 09:16:23 pm Alex Williamson wrote: > On Tue, 2010-06-08 at 14:21 -0700, Tom Lyon wrote: > > +int vfio_dma_unmap_dm(struct vfio_listener *listener, struct vfio_dma_map *dmp) > > +{ > > + unsigned long start, npage; > > + struct dma_map_page *mlp; > > + struct list_head *pos, *pos2; > > + int ret; > > + > > + start = dmp->vaddr & ~PAGE_SIZE; > > + npage = dmp->size >> PAGE_SHIFT; > > + > > + ret = -ENXIO; > > + mutex_lock(&listener->vdev->dgate); > > + list_for_each_safe(pos, pos2, &listener->dm_list) { > > + mlp = list_entry(pos, struct dma_map_page, list); > > + if (dmp->vaddr != mlp->vaddr || mlp->npage != npage) > > + continue; > > + ret = 0; > > + vfio_dma_unmap(listener, mlp); > > + break; > > + } > > Hi Tom, > > Shouldn't we be matching the mlp based on daddr instead of vaddr? We > can have multiple dma address pointing at the same virtual address, so > dma address is the unique element. I'm also nervous about this dm_list. > For qemu device assignment, we're potentially statically mapping many GB > of iova space. It seems like this could get incredibly bloated and > slow. Thanks, > > Alex In weird circumstances, differing user vaddrs could reolve to the same physical address, so the uniqueness of any mapping is the . Yes, a linear list is slow, but does qemu need a lot of mappings, or just big ones? > >