iommu/arm-smmu-v3: Add missing S2FWB feature detection

commit 45e00e3
Author: Aneesh Kumar K.V (Arm) <[email protected]>
Date: Tue Apr 8 09:03:51 2025 +0530

    iommu/arm-smmu-v3: Add missing S2FWB feature detection

    Commit 67e4fe3 ("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: 67e4fe3 ("iommu/arm-smmu-v3: Use S2FWB for NESTED domains")
    Signed-off-by: Aneesh Kumar K.V (Arm) <[email protected]>
    Reviewed-by: Jason Gunthorpe <[email protected]>
    Reviewed-by: Nicolin Chen <[email protected]>
    Reviewed-by: Pranjal Shrivastava <[email protected]>
    Link: https://lore.kernel.org/r/[email protected]
    Signed-off-by: Will Deacon <[email protected]>

(cherry picked from commit 45e00e3)
Signed-off-by: Jerry Snitselaar <[email protected]>
Upstream-Status: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
JIRA: https://issues.redhat.com/browse/RHEL-89891

Author: snits

drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c

@@ -4429,6 +4429,8 @@ 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);