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

[Yi Liu <yi.l.liu@intel.com>]

On 2025/3/28 22:40, Jason Gunthorpe wrote:
> 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

looks good to me. thanks.

-- 
Regards,
Yi Liu