Hi Lu, On Fri, 14 Jan 2022 11:12:45 +0800, Lu Baolu <[email protected]> wrote:
> On 1/14/22 11:11 AM, Jacob Pan wrote: > > On Fri, 14 Jan 2022 08:58:53 +0800, Lu Baolu<[email protected]> > > wrote: > > > >> Hi Jacob, > >> > >> On 1/13/22 9:23 PM, Jacob Pan wrote: > >>> During PCI bus rescan, adding new devices involve two notifiers. > >>> 1. dmar_pci_bus_notifier() > >>> 2. iommu_bus_notifier() > >>> The current code sets #1 as low priority (INT_MIN) which resulted in > >>> #2 being invoked first. The result is that struct device pointer > >>> cannot be found in DRHD search for the new device's DMAR/IOMMU. > >>> Subsequently, the device is put under the "catch-all" IOMMU instead > >>> of the correct one. > >>> > >>> This could cause system hang when device TLB invalidation is sent to > >>> the wrong IOMMU. Invalidation timeout error or hard lockup can be > >>> observed. > >>> > >>> This patch fixes the issue by setting a higher priority for > >>> dmar_pci_bus_notifier. DRHD search for a new device will find the > >>> correct IOMMU. > >>> > >>> Fixes: 59ce0515cdaf ("iommu/vt-d: Update DRHD/RMRR/ATSR device scope") > >>> Reported-by: Zhang, Bernice<[email protected]> > >>> Signed-off-by: Jacob Pan<[email protected]> > >>> --- > >>> drivers/iommu/intel/dmar.c | 2 +- > >>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>> > >>> diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c > >>> index 915bff76fe96..5d07e5b89c2e 100644 > >>> --- a/drivers/iommu/intel/dmar.c > >>> +++ b/drivers/iommu/intel/dmar.c > >>> @@ -385,7 +385,7 @@ static int dmar_pci_bus_notifier(struct > >>> notifier_block *nb, > >>> static struct notifier_block dmar_pci_bus_nb = { > >>> .notifier_call = dmar_pci_bus_notifier, > >>> - .priority = INT_MIN, > >>> + .priority = INT_MAX, > >>> }; > >>> > >>> static struct dmar_drhd_unit * > >>> > >> Nice catch! dmar_pci_bus_add_dev() should take place*before* > >> iommu_probe_device(). This change enforces this with a higher notifier > >> priority for dmar callback. > >> > >> Comparably, dmar_pci_bus_del_dev() should take place*after* > >> iommu_release_device(). Perhaps we can use two notifiers, one for > >> ADD_DEVICE (with .priority=INT_MAX) and the other for REMOVE_DEVICE > >> (with .priority=INT_MIN)? > >> > > Since device_to_iommu() lookup in intel_iommu_release_device() only > > checks if device is under "an" IOMMU, not "the" IOMMU. Then the remove > > path order is not needed, right? > > > > I know this is not robust, but having so many notifiers with implicit > > priority is not clean either. > > > > Perhaps, we should have explicit priority defined around iommu_bus > > notifier? i.e. > > > > @@ -1841,6 +1841,7 @@ static int iommu_bus_init(struct bus_type *bus, > > const struct iommu_ops *ops) return -ENOMEM; > > nb->notifier_call = iommu_bus_notifier; > > > > + nb->priority = IOMMU_BUS_NOTIFY_PRIORITY; > > > > > > static struct notifier_block dmar_pci_bus_add_nb = { > > .notifier_call = dmar_pci_bus_notifier, > > - .priority = INT_MIN, > > + .priority = IOMMU_BUS_NOTIFY_PRIORITY + 1, > > }; > > > > static struct notifier_block dmar_pci_bus_remove_nb = { > > .notifier_call = dmar_pci_bus_notifier, > > - .priority = INT_MIN, > > + .priority = IOMMU_BUS_NOTIFY_PRIORITY - 1, > > }; > > IOMMU_BUS_NOTIFY_PRIORITY by default is 0. So you can simply use 1 and > -1? Adding a comment around it will be helpful. > Yeah, I will add comment. Thanks, Jacob _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
