iommu/vt-d: Check capability before disabling protected memory

The spec states in 10.4.16 that the Protected Memory Enable
Register should be treated as read-only for implementations
not supporting protected memory regions (PLMR and PHMR fields
reported as Clear in the Capability register).

Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: mark gross <mgross@intel.com>
Suggested-by: Ashok Raj <ashok.raj@intel.com>
Fixes: f8bab73515ca5 ("intel-iommu: PMEN support")
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 87274b54febd..f002d47d2f27 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -1538,6 +1538,9 @@ static void iommu_disable_protect_mem_regions(struct intel_iommu *iommu)
         u32 pmen;
         unsigned long flags;
 
+        if (!cap_plmr(iommu->cap) && !cap_phmr(iommu->cap))
+                return;
+
         raw_spin_lock_irqsave(&iommu->register_lock, flags);
         pmen = readl(iommu->reg + DMAR_PMEN_REG);
         pmen &= ~DMA_PMEN_EPM;