[RFC 7/7] iommu/vt-d: Always set DMA_PTE_READ if the iommu doens't support zero length reads

[Tom Murphy]

To match the dma-ops api path the DMA_PTE_READ should be set if ZLR
isn't supported in the iommu

Signed-off-by: Tom Murphy <tmurphy@xxxxxxxxxx>
---
 drivers/iommu/intel-iommu.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 980fc4816d72..e78b0000056d 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4378,6 +4378,17 @@ static void intel_iommu_detach_device(struct iommu_domain *domain,
 	dmar_remove_one_dev_info(dev);
 }
 
+static bool supports_zlr(struct dmar_domain *domain)
+{
+	int i;
+
+	for_each_domain_iommu(i, domain) {
+		if (cap_zlr(g_iommus[i]->cap))
+			return true;
+	}
+	return false;
+}
+
 static int intel_iommu_map(struct iommu_domain *domain,
 			   unsigned long iova, phys_addr_t hpa,
 			   size_t size, int iommu_prot)
@@ -4391,7 +4402,7 @@ static int intel_iommu_map(struct iommu_domain *domain,
 	if (dmar_domain == si_domain && hw_pass_through)
 		return 0;
 
-	if (iommu_prot & IOMMU_READ)
+	if (iommu_prot & IOMMU_READ || !supports_zlr(dmar_domain))
 		prot |= DMA_PTE_READ;
 	if (iommu_prot & IOMMU_WRITE)
 		prot |= DMA_PTE_WRITE;
-- 
2.17.1