[PATCH 2/2] iommu/tegra241-cmdqv: Update uAPI to clarify HYP_OWN requirement

[Nicolin Chen]

>From hardware implementation perspective, a guest tegra241-cmdqv hardware
is different than the host hardware:
 - Host HW is backed by a VINTF (HYP_OWN=1)
 - Guest HW is backed by a VINTF (HYP_OWN=0)

The kernel driver has an implementation requirement of the HYP_OWN bit in
the VM. So, VMM must follow that to allow the same copy of Linux to work.

Add this requirement to the uAPI, which is currently missing.

Fixes: 4dc0d12474f9 ("iommu/tegra241-cmdqv: Add user-space use support")
Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
---
 include/uapi/linux/iommufd.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
index 1dafbc552d37d..f63edbe71d542 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -1052,6 +1052,11 @@ struct iommu_fault_alloc {
 enum iommu_viommu_type {
 	IOMMU_VIOMMU_TYPE_DEFAULT = 0,
 	IOMMU_VIOMMU_TYPE_ARM_SMMUV3 = 1,
+	/*
+	 * TEGRA241_CMDQV requirements (otherwise, VCMDQs will not work)
+	 * - Kernel will allocate a VINTF (HYP_OWN=0) to back this VIOMMU. So,
+	 *   VMM must wire the HYP_OWN bit to 0 in guest VINTF_CONFIG register
+	 */
 	IOMMU_VIOMMU_TYPE_TEGRA241_CMDQV = 2,
 };
 
-- 
2.43.0