Re: [PATCH v6 1/2] drm/i915/selftests: Prevent userspace mapping invalidation

[Andi Shyti <andi.shyti@kernel.org>]

Hi Krzysztof,

...

> @@ -201,6 +238,21 @@ static int __run_selftests(const char *name,
>  	pr_info(DRIVER_NAME ": Performing %s selftests with st_random_seed=0x%x st_timeout=%u\n",
>  		name, i915_selftest.random_seed, i915_selftest.timeout_ms);
>  
> +	/**
> +	 * If we are running in a kthread on a multi NUMA system and the user passed
> +	 * a valid PID of a userspace task, then we may borrow its address space
> +	 * to prepare a safe environment for the mmap selftests.
> +	 */
> +	if (!current->mm && u_pid_nr) {
> +		mm = get_mm(u_pid_nr);
> +		if (mm) {
> +			kthread_use_mm(mm);
> +			mmput_async(mm);
> +			if (unlikely(!current->mm))
> +				pr_warn("Could not set mm as current->mm\n");
> +		}
> +	}
> +
>  	/* Tests are listed in order in i915_*_selftests.h */
>  	for (; count--; st++) {

In this loop you have a few returns and we skip the mm cleanup.

Andi

>  		if (!st->enabled)
> @@ -226,6 +278,9 @@ static int __run_selftests(const char *name,
>  		 st->name, err))
>  		err = -1;
>  
> +	if (mm)
> +		kthread_unuse_mm(mm);
> +
>  	return err;
>  }