On Thu, Dec 17, 2015 at 09:43:59AM -0700, Alex Williamson wrote: <...> > > > > > > > > > > > > Also I need to disable VFIO_CHECK_EXTENSION ioctl, because in > > > > > > vfio > > > > > > module, > > > > > > container->noiommu is not set before doing a > > > > > > vfio_group_set_container() > > > > > > and vfio_for_each_iommu_driver selects wrong driver. > > > > > > > > > > Running CHECK_EXTENSION on a container without the group > > > > > attached is > > > > > only going to tell you what extensions vfio is capable of, not > > > > > necessarily what extensions are available to you with that > > > > > group. > > > > > Is this just a general dpdk- vfio ordering bug? > > > > > > > > Yes, that is how VFIO was implemented in DPDK. I was under the > > > > impression that checking extension before assigning devices was > > > > the > > > > correct way to do things, so as to not to try anything we know > > > > would > > > > fail anyway. Does this imply that CHECK_EXTENSION needs to be > > > > called > > > > on both container and groups (or just on groups)? > > > > > > Hmm, in Documentation/vfio.txt we do give the following algorithm: > > > > > > ????????if (ioctl(container, VFIO_GET_API_VERSION) != > > > VFIO_API_VERSION) > > > ????????????????/* Unknown API version */ > > > > > > ????????if (!ioctl(container, VFIO_CHECK_EXTENSION, > > > VFIO_TYPE1_IOMMU)) > > > ????????????????/* Doesn't support the IOMMU driver we want. */ > > > ????????... > > > > > > That's just going to query each iommu driver and we can't yet say > > > whether > > > the group the user attaches to the container later will actually > > > support that > > > extension until we try to do it, that would come at VFIO_SET_IOMMU. > > > ?So is > > > it perhaps a vfio bug that we're not advertising no-iommu until the > > > group is > > > attached? ?After all, we are capable of it with just an empty > > > container, just > > > like we are with type1, but we're going to fail SET_IOMMU for the > > > wrong > > > combination. > > > ?This is exactly the sort of thing that makes me glad we reverted > > > it without > > > feedback from a working user driver. ?Thanks, > > > > Whether it should be considered a "bug" in VFIO or "by design" is up > > to you, of course, but at least according to the VFIO documentation, > > we are meant to check for type 1 extension and then attach devices, > > so it would be expected to get VFIO_NOIOMMU_IOMMU marked as supported > > even without any devices attached to the container (just like we get > > type 1 as supported without any devices attached). Having said that, > > if it was meant to attach devices first and then check the > > extensions, then perhaps the documentation should also point out that > > fact (or perhaps I missed that detail in my readings of the docs, in > > which case my apologies). > > Hi Anatoly, > > Does the below patch make it behave more like you'd expect. ?This > applies to v4.4-rc4, I'd fold this into the base patch if we > reincorporate it to a future kernel. ?Thanks, > > Alex > > commit 88d4dcb6b77624965f0b45b5cd305a2b4a105c94 > Author: Alex Williamson <alex.williamson at redhat.com> > Date:???Wed Dec 16 19:02:01 2015 -0700 > > ????vfio: Fix no-iommu CHECK_EXTENSION > ???? > ????Previously the no-iommu iommu driver was only visible when the > ????container had an attached no-iommu group.??This means that > ????CHECK_EXTENSION on and empty container couldn't report the possibility > ????of using VFIO_NOIOMMU_IOMMU.??We report TYPE1 whether or not the user > ????can make use of it with the group, so this is inconsistent.??Add the > ????no-iommu iommu to the list of iommu drivers when enabled via module > ????option, but skip all the others if the container is attached to a > ????no-iommu groups.??Note that tainting is now done with the "unsafe" > ????module callback rather than explictly within vfio. > ???? > ????Also fixes module option and module description name inconsistency. > ???? > ????Also make vfio_noiommu_ops const. > ???? > ????Signed-off-by: Alex Williamson <alex.williamson at redhat.com>
Hi Alex, I got following crash with this update: [ +0.046973] BUG: unable to handle kernel NULL pointer dereference at (null) [ +0.000031] IP: [<ffffffff813b92cf>] __list_add+V0x1f/0xc0 [ +0.000024] PGD 0 [ +0.000010] Oops: 0000 [#1] SMP ... [ +0.000028] Call Trace: [ +0.000014] [<ffffffff81777301>] __mutex_lock_slowpath+0x91/0x110 [ +0.000022] [<ffffffff817773a3>] mutex_lock+0x23/0x40 [ +0.000020] [<ffffffffa0370c00>] vfio_register_iommu_driver+0x40/0xc0 [vfio] [ +0.000025] [<ffffffffa0370cd1>] noiommu_param_set+0x51/0x60 [vfio] [ +0.000022] [<ffffffff810bbe3e>] parse_args+0x1be/0x4a0 [ +0.000021] [<ffffffff81121ea0>] load_module+0xe30/0x2730 [ +0.000942] [<ffffffff8111f500>] ? __symbol_put+0x60/0x60 [ +0.000921] [<ffffffff81223f60>] ? kernel_read+0x50/0x80 [ +0.000917] [<ffffffff811239f9>] SyS_finit_module+0xb9/0xf0 [ +0.000925] [<ffffffff817796ae>] entry_SYSCALL_64_fastpath+0x12/0x71 > -static struct vfio_iommu_driver vfio_noiommu_driver = { > - .ops = &vfio_noiommu_ops, > +static int noiommu_param_set(const char *val, const struct kernel_param *kp) > +{ > + int ret; > + > + if (!val) > + val = "1"; > + > + ret = strtobool(val, kp->arg); > + if (ret) > + return ret; > + > + if (noiommu) > + ret = vfio_register_iommu_driver(&vfio_noiommu_ops); Is it possible that kernel_param_ops->set() called before module_init() that initializes the mutex. https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/kernel/module.c?id=refs/tags/v4.4-rc5#n3517 > + else > + vfio_unregister_iommu_driver(&vfio_noiommu_ops); > + > + return ret; > +} > + > +static const struct kernel_param_ops noiommu_param_ops = { > + .flags = KERNEL_PARAM_OPS_FL_NOARG, > + .set = noiommu_param_set, > + .get = param_get_bool, > ?}; > ? Thanks, ferruh