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

[ Upstream commit 5bb71fc790a88d063507dc5d445ab8b14e845591 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 86e349614e21a4fb8cefab62a66cfa39e56d21b1..28feb1744710eb0d903a4234042e35fd792aecf4 100644 (file)
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -1636,6 +1636,9 @@ 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;