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 08:58:53 +0800 |
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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)?
Best regards, baolu
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