linux-kernel - [PATCH] iommu/arm-smmu-v3: Add missing S2FWB feature detection

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Message-ID: <20250408033351.1012411-1-aneesh.kumar@kernel.org>
Date: Tue,  8 Apr 2025 09:03:51 +0530
From: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@...nel.org>
To: iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Cc: will@...nel.org,
	robin.murphy@....com,
	jgg@...pe.ca,
	nicolinc@...dia.com,
	jsnitsel@...hat.com,
	praan@...gle.com,
	kevin.tian@...el.com,
	ddutile@...hat.com,
	"Aneesh Kumar K.V (Arm)" <aneesh.kumar@...nel.org>
Subject: [PATCH] iommu/arm-smmu-v3: Add missing S2FWB feature detection

Commit 67e4fe398513 ("iommu/arm-smmu-v3: Use S2FWB for NESTED domains")
introduced S2FWB usage but omitted the corresponding feature detection.
As a result, vIOMMU allocation fails on FVP in arm_vsmmu_alloc(), due to
the following check:

	if (!arm_smmu_master_canwbs(master) &&
	    !(smmu->features & ARM_SMMU_FEAT_S2FWB))
		return ERR_PTR(-EOPNOTSUPP);

This patch adds the missing detection logic to prevent allocation
failure when S2FWB is supported.

Fixes: 67e4fe398513 ("iommu/arm-smmu-v3: Use S2FWB for NESTED domains")
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@...nel.org>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 2 ++
 1 file changed, 2 insertions(+)

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 358072b4e293..c7d297ceabdb 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -4405,6 +4405,8 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
 	reg = readl_relaxed(smmu->base + ARM_SMMU_IDR3);
 	if (FIELD_GET(IDR3_RIL, reg))
 		smmu->features |= ARM_SMMU_FEAT_RANGE_INV;
+	if (FIELD_GET(IDR3_FWB, reg))
+		smmu->features |= ARM_SMMU_FEAT_S2FWB;
 
 	/* IDR5 */
 	reg = readl_relaxed(smmu->base + ARM_SMMU_IDR5);
-- 
2.43.0