Messages in this thread | | | Subject | Re: [PATCH] iommu/vt-d: Fix PCI bus rescan device hot add | From | Lu Baolu <> | Date | Fri, 14 Jan 2022 11:12:45 +0800 |
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On 1/14/22 11:11 AM, Jacob Pan wrote: > On Fri, 14 Jan 2022 08:58:53 +0800, Lu Baolu<baolu.lu@linux.intel.com> > 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<bernice.zhang@intel.com> >>> Signed-off-by: Jacob Pan<jacob.jun.pan@linux.intel.com> >>> --- >>> 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.
Best regards, baolu
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