From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42218) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zep2N-0001FD-Nc for qemu-devel@nongnu.org; Wed, 23 Sep 2015 14:45:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zep2K-00062S-I3 for qemu-devel@nongnu.org; Wed, 23 Sep 2015 14:45:03 -0400 References: <1442495357-26547-1-git-send-email-david@gibson.dropbear.id.au> <1442495357-26547-7-git-send-email-david@gibson.dropbear.id.au> From: Laurent Vivier Message-ID: <5602F326.2060403@redhat.com> Date: Wed, 23 Sep 2015 20:44:54 +0200 MIME-Version: 1.0 In-Reply-To: <1442495357-26547-7-git-send-email-david@gibson.dropbear.id.au> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC PATCH 06/10] vfio: Allow hotplug of containers onto existing guest IOMMU mappings List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson , alex.williamson@redhat.com, aik@ozlabs.ru, gwshan@linux.vnet.ibm.com Cc: pbonzini@redhat.com, thuth@redhat.com, qemu-ppc@nongnu.org, qemu-devel@nongnu.org On 17/09/2015 15:09, David Gibson wrote: > At present the memory listener used by vfio to keep host IOMMU mappings > in sync with the guest memory image assumes that if a guest IOMMU > appears, then it has no existing mappings. > > This may not be true if a VFIO device is hotplugged onto a guest bus > which didn't previously include a VFIO device, and which has existing > guest IOMMU mappings. > > Therefore, use the memory_region_register_iommu_notifier_replay() > function in order to fix this case, replaying existing guest IOMMU > mappings, bringing the host IOMMU into sync with the guest IOMMU. > > Signed-off-by: David Gibson > --- > hw/vfio/common.c | 34 +++++++++++++++++++--------------- > 1 file changed, 19 insertions(+), 15 deletions(-) > > diff --git a/hw/vfio/common.c b/hw/vfio/common.c > index daaac48..543c38e 100644 > --- a/hw/vfio/common.c > +++ b/hw/vfio/common.c > @@ -312,6 +312,22 @@ out: > rcu_read_unlock(); > } > > +static hwaddr vfio_container_granularity(VFIOContainer *container) > +{ > + uint64_t pgsize; > + > + assert(container->iommu_data.iova_pgsizes); > + > + /* Find the smallest page size supported by the IOMMU */ > + for (pgsize = 1; pgsize; pgsize <<= 1) { > + if (pgsize & container->iommu_data.iova_pgsizes) { > + return pgsize; > + } > + } Perhaps we can use gcc builtin ? return 1 << ctz64(container->iommu_data.iova_pgsizes); > + /* Can't happen */ > + assert(0); > +} > + > static void vfio_listener_region_add(MemoryListener *listener, > MemoryRegionSection *section) > { > @@ -371,26 +387,14 @@ static void vfio_listener_region_add(MemoryListener *listener, > * would be the right place to wire that up (tell the KVM > * device emulation the VFIO iommu handles to use). > */ > - /* > - * This assumes that the guest IOMMU is empty of > - * mappings at this point. > - * > - * One way of doing this is: > - * 1. Avoid sharing IOMMUs between emulated devices or different > - * IOMMU groups. > - * 2. Implement VFIO_IOMMU_ENABLE in the host kernel to fail if > - * there are some mappings in IOMMU. > - * > - * VFIO on SPAPR does that. Other IOMMU models may do that different, > - * they must make sure there are no existing mappings or > - * loop through existing mappings to map them into VFIO. > - */ > giommu = g_malloc0(sizeof(*giommu)); > giommu->iommu = section->mr; > giommu->container = container; > giommu->n.notify = vfio_iommu_map_notify; > QLIST_INSERT_HEAD(&container->giommu_list, giommu, giommu_next); > - memory_region_register_iommu_notifier(giommu->iommu, &giommu->n); > + > + memory_region_register_iommu_notifier_replay(giommu->iommu, &giommu->n, > + vfio_container_granularity(container), false); > > return; > } >