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

Ganapatrao Kulkarni
2023-02-02T12:42:37Z

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@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