linux-kernel - [PATCH v2 2/2] iommu/arm-smmu-v3: Configure STU of a PF if ATS is not enabled.

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Message-Id: <20230228042137.1941024-3-gankulkarni@os.amperecomputing.com>
Date:   Mon, 27 Feb 2023 20:21:37 -0800
From:   Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>
To:     linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
        joro@...tes.org, bhelgaas@...gle.com, robin.murphy@....com,
        will@...nel.org
Cc:     jean-philippe@...aro.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com,
        darren@...amperecomputing.com, scott@...amperecomputing.com,
        gankulkarni@...amperecomputing.com
Subject: [PATCH v2 2/2] iommu/arm-smmu-v3: Configure STU of a PF if ATS is not enabled.

When the host kernel is booted with iommu passthrough mode, PF and VFs
are enumerated with iommu/smmu domain set to bypass mode.
In bypass mode, ATS is not enabled on all VFs and associated PF.
When VFs are attached to a VM, the corresponding iommu domain is set to
SMMU translation mode and smmu-v3 driver try to enable the ATS and fails
due to invalid STU of a PF.

Adding a fix to configure STU of a PF while enumerating in passthrough
mode.

Signed-off-by: Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 25 ++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

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 f2425b0f0cd6..b218ef0bf001 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2292,6 +2292,23 @@ static bool arm_smmu_ats_supported(struct arm_smmu_master *master)
 	return dev_is_pci(dev) && pci_ats_supported(to_pci_dev(dev));
 }
 
+static void arm_smmu_ats_stu_init(struct arm_smmu_master *master)
+{
+	size_t stu;
+	struct pci_dev *pdev;
+	struct arm_smmu_device *smmu = master->smmu;
+
+	if (master->ats_enabled)
+		return;
+
+	/* Smallest Translation Unit: log2 of the smallest supported granule */
+	stu = __ffs(smmu->pgsize_bitmap);
+	pdev = to_pci_dev(master->dev);
+
+	if (pci_ats_stu_configure(pdev, stu))
+		dev_err(master->dev, "Failed to configure ATS STU (%zu)\n", stu);
+}
+
 static void arm_smmu_enable_ats(struct arm_smmu_master *master)
 {
 	size_t stu;
@@ -2404,6 +2421,7 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 	struct arm_smmu_device *smmu;
 	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
 	struct arm_smmu_master *master;
+	bool ats_supported;
 
 	if (!fwspec)
 		return -ENOENT;
@@ -2446,9 +2464,10 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 	}
 
 	master->domain = smmu_domain;
+	ats_supported = arm_smmu_ats_supported(master);
 
 	if (smmu_domain->stage != ARM_SMMU_DOMAIN_BYPASS)
-		master->ats_enabled = arm_smmu_ats_supported(master);
+		master->ats_enabled = ats_supported;
 
 	arm_smmu_install_ste_for_dev(master);
 
@@ -2458,6 +2477,10 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 
 	arm_smmu_enable_ats(master);
 
+	/* Configure ATS STU of a PF in passthrough */
+	if (!master->ats_enabled && ats_supported)
+		arm_smmu_ats_stu_init(master);
+
 out_unlock:
 	mutex_unlock(&smmu_domain->init_mutex);
 	return ret;
-- 
2.38.1