From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40651) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eMRcT-0000LZ-Bx for qemu-devel@nongnu.org; Tue, 05 Dec 2017 23:47:42 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eMRcP-0002B7-0f for qemu-devel@nongnu.org; Tue, 05 Dec 2017 23:47:41 -0500 Received: from mga03.intel.com ([134.134.136.65]:32967) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eMRcO-0002A8-MM for qemu-devel@nongnu.org; Tue, 05 Dec 2017 23:47:36 -0500 Date: Wed, 6 Dec 2017 12:31:03 +0800 From: "Liu, Yi L" Message-ID: <20171206043103.GB1164@sky-dev> References: <20171205205409.5348.53070.stgit@gimli.home> <20171206024443.GA1164@sky-dev> <20171205201258.6111c71c@t450s.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171205201258.6111c71c@t450s.home> Subject: Re: [Qemu-devel] [PATCH for-2.11] vfio: Fix vfio-kvm group registration List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alex Williamson Cc: qemu-devel@nongnu.org, aik@ozlabs.ru, eric.auger@redhat.com On Tue, Dec 05, 2017 at 08:12:58PM -0700, Alex Williamson wrote: > On Wed, 6 Dec 2017 10:44:43 +0800 > "Liu, Yi L" wrote: > > > On Tue, Dec 05, 2017 at 02:09:07PM -0700, Alex Williamson wrote: > > > Commit 8c37faa475f3 ("vfio-pci, ppc64/spapr: Reorder group-to-container > > > attaching") moved registration of groups with the vfio-kvm device from > > > vfio_get_group() to vfio_connect_container(), but it missed the case > > > where a group is attached to an existing container and takes an early > > > exit. Perhaps this is a less common case on ppc64/spapr, but on x86 > > > (without viommu) all groups are connected to the same container and > > > thus only the first group gets registered with the vfio-kvm device. > > > This becomes a problem if we then hot-unplug the devices associated > > > with that first group and we end up with KVM being misinformed about > > > any vfio connections that might remain. Fix by including the call to > > > vfio_kvm_device_add_group() in this early exit path. > > > > > > Fixes: 8c37faa475f3 ("vfio-pci, ppc64/spapr: Reorder group-to-container attaching") > > > Cc: qemu-stable@nongnu.org # qemu-2.10+ > > > Signed-off-by: Alex Williamson > > > --- > > > > > > This bug also existed in QEMU 2.10, but I think the fix is sufficiently > > > obvious (famous last words) to propose for 2.11 at this late date. If > > > the first group is hot unplugged then KVM may revert to code emulation > > > that assumes no non-coherent DMA is present on some systems. Also for > > > KVMGT, if the vGPU is not the first device registered, then the > > > notifier to enable linkages to KVM would not be called. Please review. > > > Thanks, > > > > Alex, for x86, I suppose it doesn't exist in the case which viommu is exposed > > to guest? > > With viommu, I believe each group would be in its own AddressSpace and > therefore get a separate container, so I don't think it'd be an issue. > It's only subsequent groups added to the same container which are > missed. Thanks, agree, thanks for the confirm. It's a nice fix~ Regards, Yi L > > > > hw/vfio/common.c | 1 + > > > 1 file changed, 1 insertion(+) > > > > > > diff --git a/hw/vfio/common.c b/hw/vfio/common.c > > > index 7b2924c0ef19..7007878e345e 100644 > > > --- a/hw/vfio/common.c > > > +++ b/hw/vfio/common.c > > > @@ -968,6 +968,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as, > > > if (!ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &container->fd)) { > > > group->container = container; > > > QLIST_INSERT_HEAD(&container->group_list, group, container_next); > > > + vfio_kvm_device_add_group(group); > > > return 0; > > > } > > > } > > > > > > >