iommufd: vfio compatibility extension check for noiommu mode

[ Upstream commit 7147ec8 ]

VFIO_CHECK_EXTENSION should return false for TYPE1_IOMMU variants when
in NO-IOMMU mode and IOMMUFD compat container is set. This change makes
the behavior match VFIO_CONTAINER in noiommu mode. It also prevents
userspace from incorrectly attempting to use TYPE1 IOMMU operations
in a no-iommu context.

Fixes: d624d66 ("iommufd: vfio container FD ioctl compatibility")
Link: https://patch.msgid.link/r/20260213183636.3340-1-jacob.pan@linux.microsoft.com
Signed-off-by: Jacob Pan <jacob.pan@linux.microsoft.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: jacobpan

drivers/iommu/iommufd/vfio_compat.c

@@ -283,7 +283,7 @@ static int iommufd_vfio_check_extension(struct iommufd_ctx *ictx,
 	case VFIO_TYPE1_IOMMU:
 	case VFIO_TYPE1v2_IOMMU:
 	case VFIO_UNMAP_ALL:
-		return 1;
+		return !ictx->no_iommu_mode;
 
 	case VFIO_NOIOMMU_IOMMU:
 		return IS_ENABLED(CONFIG_VFIO_NOIOMMU);