Re: [PATCH] iommufd: Test attach before detaching pasid

[Jason Gunthorpe <jgg@nvidia.com>]

On Fri, Mar 28, 2025 at 06:34:48AM -0700, Yi Liu wrote:
> Check if the pasid has been attached before going further in the detach
> path. This makes this path more robust. Add a selftest as well.
> 
> Reported-by: Lai Yi <yi1.lai@linux.intel.com>
> Closes: https://lore.kernel.org/linux-iommu/Z+X0tzxhiaupJT7b@ly-workstation/#t
> Fixes: c0e301b2978d ("iommufd/device: Add pasid_attach array to track per-PASID attach")
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> ---
>  drivers/iommu/iommufd/device.c          | 7 +++++++
>  tools/testing/selftests/iommu/iommufd.c | 6 ++++++
>  2 files changed, 13 insertions(+)
> 
> diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
> index 2307daad65c0..375dd262f431 100644
> --- a/drivers/iommu/iommufd/device.c
> +++ b/drivers/iommu/iommufd/device.c
> @@ -644,6 +644,11 @@ iommufd_hw_pagetable_detach(struct iommufd_device *idev, ioasid_t pasid)
>  
>  	mutex_lock(&igroup->lock);
>  	attach = xa_load(&igroup->pasid_attach, pasid);
> +	if (WARN_ON(!attach)) {
> +		mutex_unlock(&igroup->lock);
> +		return NULL;
> +	}

We can't trigger a WARN_ON during the test suite!

#  RUN           iommufd_device_pasid.no_pasid.pasid_attach ...
[   23.723948] iommufd_mock iommufd_mock0: Adding to iommu group 0
[   23.724532] iommufd_mock iommufd_mock1: Adding to iommu group 1
[   23.724722] ------------[ cut here ]------------
[   23.725194] WARNING: CPU: 5 PID: 1169 at drivers/iommu/iommufd/device.c:647 iommufd_hw_pagetable_detach+0x1e7/0x230 [iommufd]
[   23.725350] Modules linked in: iommufd
[   23.725406] CPU: 5 UID: 0 PID: 1169 Comm: iommufd Not tainted 6.14.0-rc2+ #1

Just drop the WARN_ON check right?

I took it like that, please let me know

Jason