Re: [PATCH v1 1/2] iommufd: Make attach_handle generic than fault specific

[Jason Gunthorpe <jgg@nvidia.com>]

On Mon, Feb 03, 2025 at 09:00:54PM -0800, Nicolin Chen wrote:
> "attach_handle" was added exclusively for the iommufd_fault_iopf_handler()
> used by IOPF/PRI use cases. Now, both the MSI and PASID series require to
> reuse the attach_handle for non-fault cases.
> 
> Add a set of new attach/detach/replace helpers that does the attach_handle
> allocation/releasing/replacement in the common path and also handles those
> fault specific routines such as iopf enabling/disabling and auto response.
> 
> This covers both non-fault and fault cases in a clean way, replacing those
> inline helpers in the header. The following patch will clean up those old
> helpers in the fault.c file.
> 
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
> ---
>  drivers/iommu/iommufd/iommufd_private.h |  33 +-------
>  drivers/iommu/iommufd/device.c          | 101 ++++++++++++++++++++++++
>  drivers/iommu/iommufd/fault.c           |   8 +-
>  3 files changed, 109 insertions(+), 33 deletions(-)

I am going to add some lockdeps to this:

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index 360ba3ed85455e..0786290b4056df 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -360,6 +360,8 @@ static int iommufd_hwpt_attach_device(struct iommufd_hw_pagetable *hwpt,
 	struct iommufd_attach_handle *handle;
 	int rc;
 
+	lockdep_assert_held(&idev->igroup->lock);
+
 	handle = kzalloc(sizeof(*handle), GFP_KERNEL);
 	if (!handle)
 		return -ENOMEM;
@@ -391,6 +393,8 @@ iommufd_device_get_attach_handle(struct iommufd_device *idev)
 {
 	struct iommu_attach_handle *handle;
 
+	lockdep_assert_held(&idev->igroup->lock);
+
 	handle =
 		iommu_attach_handle_get(idev->igroup->group, IOMMU_NO_PASID, 0);
 	if (IS_ERR(handle))


I think the one in get_attach_handle is important to discourage misuse
of that ..

Thanks,
Jason