iommu/vt-d: Fix RID2PASID setup/teardown failure

The IOMMU driver shares the pasid table for PCI alias devices. When the
RID2PASID entry of the shared pasid table has been filled by the first
device, the subsequent device will encounter the "DMAR: Setup RID2PASID
failed" failure as the pasid entry has already been marked as present.
As the result, the IOMMU probing process will be aborted.

On the contrary, when any alias device is hot-removed from the system,
for example, by writing to /sys/bus/pci/devices/.../remove, the shared
RID2PASID will be cleared without any notifications to other devices.
As the result, any DMAs from those rest devices are blocked.

Sharing pasid table among PCI alias devices could save two memory pages
for devices underneath the PCIe-to-PCI bridges. Anyway, considering that
those devices are rare on modern platforms that support VT-d in scalable
mode and the saved memory is negligible, it's reasonable to remove this
part of immature code to make the driver feasible and stable.

Fixes: ef848b7e5a6a0 ("iommu/vt-d: Setup pasid entry for RID2PASID support")
Reported-by: Chenyi Qiang <chenyi.qiang@intel.com>
Reported-by: Ethan Zhao <haifeng.zhao@linux.intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Ethan Zhao <haifeng.zhao@linux.intel.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20220623065720.727849-1-baolu.lu@linux.intel.com
Link: https://lore.kernel.org/r/20220625133430.2200315-2-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

1 files changed, 0 insertions, 24 deletions

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 44016594831d..5c0dce78586a 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -320,30 +320,6 @@ EXPORT_SYMBOL_GPL(intel_iommu_gfx_mapped);
 DEFINE_SPINLOCK(device_domain_lock);
 static LIST_HEAD(device_domain_list);
 
-/*
- * Iterate over elements in device_domain_list and call the specified
- * callback @fn against each element.
- */
-int for_each_device_domain(int (*fn)(struct device_domain_info *info,
-				     void *data), void *data)
-{
-	int ret = 0;
-	unsigned long flags;
-	struct device_domain_info *info;
-
-	spin_lock_irqsave(&device_domain_lock, flags);
-	list_for_each_entry(info, &device_domain_list, global) {
-		ret = fn(info, data);
-		if (ret) {
-			spin_unlock_irqrestore(&device_domain_lock, flags);
-			return ret;
-		}
-	}
-	spin_unlock_irqrestore(&device_domain_lock, flags);
-
-	return 0;
-}
-
 const struct iommu_ops intel_iommu_ops;
 
 static bool translation_pre_enabled(struct intel_iommu *iommu)