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

LuBaolu · joergroedel · commit 5bb71fc790a8 · 2019-03-22T12:02:26.000+01:00
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: f8bab73 ("intel-iommu: PMEN support") Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> Signed-off-by: Joerg Roedel <jroedel@suse.de>
diff --git 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;
