[PATCH] drivers/firmware: psci_checker: stash and use topology_core_cpumask for hotplug tests

[lorenzo.pieralisi@arm.com (Lorenzo Pieralisi)]

On Wed, Jul 18, 2018 at 12:25:32PM +0100, Sudeep Holla wrote:
> Commit 7f9545aa1a91 ("arm64: smp: remove cpu and numa topology
> information when hotplugging out CPU") updates the cpu topology when
> the CPU is hotplugged out. However the PSCI checker code uses the
> topology_core_cpumask pointers for some of the cpu hotplug testing.
> Since the pointer to the core_cpumask of the first CPU in the group
> is used, which when that CPU itself is hotpugged out is just set to
> itself, the testing terminates after that particular CPU is tested out.
> But the intention of this tests is to cover all the CPU in the group.
> 
> In order to support that, we need to stash the topology_core_cpumask
> before the start of the test and use that value instead of pointer to
> a cpumask which will be updated on CPU hotplug.
> 
> Fixes: 7f9545aa1a91a9a4 ("arm64: smp: remove cpu and numa topology
> 	information when hotplugging out CPU")
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
>  drivers/firmware/psci_checker.c | 30 ++++++++++++++++++++----------
>  1 file changed, 20 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/firmware/psci_checker.c b/drivers/firmware/psci_checker.c
> index bb1c068bff19..e330c6cb45f5 100644
> --- a/drivers/firmware/psci_checker.c
> +++ b/drivers/firmware/psci_checker.c
> @@ -77,21 +77,23 @@ static int psci_ops_check(void)
>  	return 0;
>  }
>  
> -static int find_cpu_groups(const struct cpumask *cpus,
> -			   const struct cpumask **cpu_groups)
> +static int find_cpu_groups(cpumask_var_t *cpu_groups)
>  {
>  	unsigned int nb = 0;
>  	cpumask_var_t tmp;
>  
>  	if (!alloc_cpumask_var(&tmp, GFP_KERNEL))
>  		return -ENOMEM;
> -	cpumask_copy(tmp, cpus);
> +	cpumask_copy(tmp, cpu_online_mask);
>  
>  	while (!cpumask_empty(tmp)) {
>  		const struct cpumask *cpu_group =
>  			topology_core_cpumask(cpumask_any(tmp));
>  
> -		cpu_groups[nb++] = cpu_group;
> +		if (cpu_groups && cpu_groups[nb])
> +			cpumask_copy(cpu_groups[nb], cpu_group);
> +
> +		nb++;
>  		cpumask_andnot(tmp, tmp, cpu_group);
>  	}
>  
> @@ -169,25 +171,31 @@ static unsigned int down_and_up_cpus(const struct cpumask *cpus,
>  static int hotplug_tests(void)
>  {
>  	int err;
> -	cpumask_var_t offlined_cpus;
> +	cpumask_var_t offlined_cpus, *cpu_groups;
>  	int i, nb_cpu_group;
> -	const struct cpumask **cpu_groups;
>  	char *page_buf;
>  
> +	/* first run to just get the number of cpu groups */
> +	nb_cpu_group = find_cpu_groups(NULL);
> +
>  	err = -ENOMEM;
>  	if (!alloc_cpumask_var(&offlined_cpus, GFP_KERNEL))
>  		return err;
> -	/* We may have up to nb_available_cpus cpu_groups. */
> -	cpu_groups = kmalloc_array(nb_available_cpus, sizeof(*cpu_groups),
> -				   GFP_KERNEL);
> +	cpu_groups = kcalloc(nb_cpu_group, sizeof(cpu_groups), GFP_KERNEL);
>  	if (!cpu_groups)
>  		goto out_free_cpus;
> +
> +	for (i = 0; i < nb_cpu_group; ++i)
> +		if (!alloc_cpumask_var(&cpu_groups[i], GFP_KERNEL))
> +			goto out_free_cpu_groups;
> +
>  	page_buf = (char *)__get_free_page(GFP_KERNEL);
>  	if (!page_buf)
>  		goto out_free_cpu_groups;
>  
>  	err = 0;
> -	nb_cpu_group = find_cpu_groups(cpu_online_mask, cpu_groups);
> +	/* second run to populate/copy the cpumask */
> +	nb_cpu_group = find_cpu_groups(cpu_groups);
>  
>  	/*
>  	 * Of course the last CPU cannot be powered down and cpu_down() should
> @@ -212,6 +220,8 @@ static int hotplug_tests(void)
>  
>  	free_page((unsigned long)page_buf);
>  out_free_cpu_groups:
> +	for (i = 0; i < nb_cpu_group; ++i)
> +		free_cpumask_var(cpu_groups[i]);
>  	kfree(cpu_groups);
>  out_free_cpus:
>  	free_cpumask_var(offlined_cpus);

Hi Sudeep,

thanks for the patch. I reckon that adding two functions, say,
alloc_cpu_groups() and free_cpu_groups() would make the code
more readable instead of relying on find_cpu_groups() to first
count then copy; it is for readability rather than correctness.

Thanks,
Lorenzo