linux-kernel - [PATCH v1 4/4] iommu/arm-smmu-v3-iommufd: Allow a shared s2

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Message-ID: <564eda8dee4bbf4c6e1d1dd9ed6bd40cc1a2df26.1741150594.git.nicolinc@nvidia.com>
Date: Tue, 4 Mar 2025 21:04:03 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: <will@...nel.org>, <robin.murphy@....com>, <jgg@...dia.com>
CC: <joro@...tes.org>, <linux-arm-kernel@...ts.infradead.org>,
	<iommu@...ts.linux.dev>, <linux-kernel@...r.kernel.org>,
	<shameerali.kolothum.thodi@...wei.com>
Subject: [PATCH v1 4/4] iommu/arm-smmu-v3-iommufd: Allow a shared s2_parent to allocate vSMMU

Now, vmids are stored in vSMMU objects. So all vSMMUs assigned to the same
VM can share a s2_parent domain. This means a vIOMMU allocation per device
behind one SMMU can be given with a s2_parent domain that's allocated per
another device behind another SMMU, i.e. s2_parent->smmu != master->smmu.

Remove the validation line to allow this use case.

Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
index 2c5a9d0abed5..9bfa5fa5bafa 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
@@ -378,9 +378,6 @@ struct iommufd_viommu *arm_vsmmu_alloc(struct device *dev,
 	if (!(smmu->features & ARM_SMMU_FEAT_NESTING))
 		return ERR_PTR(-EOPNOTSUPP);
 
-	if (s2_parent->smmu != master->smmu)
-		return ERR_PTR(-EINVAL);
-
 	/*
 	 * FORCE_SYNC is not set with FEAT_NESTING. Some study of the exact HW
 	 * defect is needed to determine if arm_vsmmu_cache_invalidate() needs
-- 
2.43.0