The Intel IOMMU driver will put devices into a static identity mapped domain during boot if the kernel parameter "iommu=pt" is used. That means the IOMMU hardware will translate a DMA address into the same memory address.

Unfortunately, hot-added devices are not subject to this. That results in some devices not working properly after hot added. A quick way to reproduce this issue is to boot a system with

iommu=pt

and, remove then readd the pci device with

echo 1 > /sys/bus/pci/devices/[pci_source_id]/remove echo 1 > /sys/bus/pci/rescan

You will find the identity mapped domain was replaced with a normal domain.

Cc: Ashok Raj ashok.raj@intel.com Cc: Jacob Pan jacob.jun.pan@linux.intel.com Cc: Fenghua Yu fenghua.yu@intel.com Cc: stable@vger.kernel.org Reported-by: Jis Ben jisben@google.com Signed-off-by: Lu Baolu baolu.lu@linux.intel.com Tested-by: James Dong xmdong@google.com --- drivers/iommu/intel-iommu.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c index af23cfc2a05e..4f77657a9c25 100644 --- a/drivers/iommu/intel-iommu.c +++ b/drivers/iommu/intel-iommu.c @@ -4564,16 +4564,19 @@ static int device_notifier(struct notifier_block *nb, if (iommu_dummy(dev)) return 0;

- if (action != BUS_NOTIFY_REMOVED_DEVICE) - return 0; - - domain = find_domain(dev); - if (!domain) - return 0; + if (action == BUS_NOTIFY_REMOVED_DEVICE) { + domain = find_domain(dev); + if (!domain) + return 0;

- dmar_remove_one_dev_info(dev); - if (!domain_type_is_vm_or_si(domain) && list_empty(&domain->devices)) - domain_exit(domain); + dmar_remove_one_dev_info(dev); + if (!domain_type_is_vm_or_si(domain) && + list_empty(&domain->devices)) + domain_exit(domain); + } else if (action == BUS_NOTIFY_ADD_DEVICE) { + if (iommu_should_identity_map(dev, 1)) + domain_add_dev_info(si_domain, dev); + }

return 0; }