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

Tom Murphy
2019-05-04T13:23:23Z

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@arista.com>
---
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