[PATCH] iommu/arm-smmu-v3: Enable PCI ATS in passthrough mode as well

[Ganapatrao Kulkarni]

The current smmu-v3 driver does not enable PCI ATS for physical functions
of ATS capable End Points when booted in smmu bypass mode
(iommu.passthrough=1). This will not allow virtual functions to enable
ATS(even though EP supports it) while they are attached to a VM using
VFIO driver.

This patch adds changes to enable ATS support for physical functions
in passthrough/bypass mode as well.

Also, adding check to avoid disabling of ATS if it is not enabled,
to avoid unnecessary call-traces.

Signed-off-by: Ganapatrao Kulkarni <gankulkarni at os.amperecomputing.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 6d5df91c5c46..5a605cb5ccef 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2313,11 +2313,16 @@ static void arm_smmu_enable_ats(struct arm_smmu_master *master)
 static void arm_smmu_disable_ats(struct arm_smmu_master *master)
 {
 	struct arm_smmu_domain *smmu_domain = master->domain;
+	struct pci_dev *pdev;
 
 	if (!master->ats_enabled)
 		return;
 
-	pci_disable_ats(to_pci_dev(master->dev));
+	pdev = to_pci_dev(master->dev);
+
+	if (pdev->ats_enabled)
+		pci_disable_ats(pdev);
+
 	/*
 	 * Ensure ATS is disabled at the endpoint before we issue the
 	 * ATC invalidation via the SMMU.
@@ -2453,8 +2458,7 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 
 	master->domain = smmu_domain;
 
-	if (smmu_domain->stage != ARM_SMMU_DOMAIN_BYPASS)
-		master->ats_enabled = arm_smmu_ats_supported(master);
+	master->ats_enabled = arm_smmu_ats_supported(master);
 
 	arm_smmu_install_ste_for_dev(master);
 
-- 
2.37.3