iommu/vt-d: Only clear real DMA device's context entries

commit 8038bdb8553313ad53bfcffcf8294dd0ab44618f upstream.

Domain context mapping can encounter issues with sub-devices of a real
DMA device. A sub-device cannot have a valid context entry due to it
potentially aliasing another device's 16-bit ID. It's expected that
sub-devices of the real DMA device uses the real DMA device's requester
when context mapping.

This is an issue when a sub-device is removed where the context entry is
cleared for all aliases. Other sub-devices are still valid, resulting in
those sub-devices being stranded without valid context entries.

The correct approach is to use the real DMA device when programming the
context entries. The insertion path is correct because device_to_iommu()
will return the bus and devfn of the real DMA device. The removal path
needs to only operate on the real DMA device, otherwise the entire
context entry would be cleared for all sub-devices of the real DMA
device.

This patch also adds a helper to determine if a struct device is a
sub-device of a real DMA device.

Fixes: 2b0140c69637e ("iommu/vt-d: Use pci_real_dma_dev() for mapping")
Cc: stable@vger.kernel.org # v5.6+
Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
Acked-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20200527165617.297470-2-jonathan.derrick@intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 0182cff2c7ac75947bf6a2e746cbe0864a8a5c15..3c3dba87c71ff3876b47f93ce822e7dd3c463a44 100644 (file)
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -2582,6 +2582,12 @@ static int domain_setup_first_level(struct intel_iommu *iommu,
                                             flags);
 }
 
+static bool dev_is_real_dma_subdevice(struct device *dev)
+{
+       return dev && dev_is_pci(dev) &&
+              pci_real_dma_dev(to_pci_dev(dev)) != to_pci_dev(dev);
+}
+
 static struct dmar_domain *dmar_insert_one_dev_info(struct intel_iommu *iommu,
                                                    int bus, int devfn,
                                                    struct device *dev,
@@ -5286,7 +5292,8 @@ static void __dmar_remove_one_dev_info(struct device_domain_info *info)
                                        PASID_RID2PASID);
 
                iommu_disable_dev_iotlb(info);
-               domain_context_clear(iommu, info->dev);
+               if (!dev_is_real_dma_subdevice(info->dev))
+                       domain_context_clear(iommu, info->dev);
                intel_pasid_free_table(info->dev);
        }