Re: [PATCH v2 07/18] nitro_enclaves: Init misc device providing the ioctl interface

Paraschiv, Andra-Irina
2020-05-25T20:50:17Z

On 22/05/2020 10:07, Greg KH wrote:
> On Fri, May 22, 2020 at 09:29:35AM +0300, Andra Paraschiv wrote:
>> +static char *ne_cpus;
>> +module_param(ne_cpus, charp, 0644);
>> +MODULE_PARM_DESC(ne_cpus, "<cpu-list> - CPU pool used for Nitro Enclaves");
> This is not the 1990's, don't use module parameters if you can help it.
> Why is this needed, and where is it documented?

This is a CPU pool that can be set by the root user and that includes
CPUs set aside to be used for the enclave(s) setup; these CPUs are
offlined. From this CPU pool, the kernel logic chooses the CPUs that are
set for the created enclave(s).

The cpu-list format is matching the same that is documented here:

https://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html

I've also thought of having a sysfs entry for the setup of this enclave
CPU pool.

>
>> +/* CPU pool used for Nitro Enclaves. */
>> +struct ne_cpu_pool {
>> + /* Available CPUs in the pool. */
>> + cpumask_var_t avail;
>> + struct mutex mutex;
>> +};
>> +
>> +static struct ne_cpu_pool ne_cpu_pool;
>> +
>> +static int ne_open(struct inode *node, struct file *file)
>> +{
>> + return 0;
>> +}
> If open does nothing, just don't even provide it.

I removed this and other file ops occurrences that do nothing for now.

>
>> +
>> +static long ne_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>> +{
>> + switch (cmd) {
>> +
>> + default:
>> + return -ENOTTY;
>> + }
>> +
>> + return 0;
>> +}
> Same for ioctl.

This logic is completed in the next patch in the series.

>
>> +
>> +static int ne_release(struct inode *inode, struct file *file)
>> +{
>> + return 0;
>> +}
> Same for release.

Done, I removed it for now.

>
>> +
>> +static const struct file_operations ne_fops = {
>> + .owner = THIS_MODULE,
>> + .llseek = noop_llseek,
>> + .unlocked_ioctl = ne_ioctl,
>> + .open = ne_open,
>> + .release = ne_release,
>> +};
>> +
>> +struct miscdevice ne_miscdevice = {
>> + .minor = MISC_DYNAMIC_MINOR,
>> + .name = NE_DEV_NAME,
>> + .fops = &ne_fops,
>> + .mode = 0660,
>> +};
>> +
>> +static int __init ne_init(void)
>> +{
>> + unsigned int cpu = 0;
>> + unsigned int cpu_sibling = 0;
>> + int rc = -EINVAL;
>> +
>> + memset(&ne_cpu_pool, 0, sizeof(ne_cpu_pool));
> Why did you just set a structure to 0 that was already initialized by
> the system to 0? Are you sure about this?

True, this is not needed. Removed the memset() call.

>
>> +
>> + if (!zalloc_cpumask_var(&ne_cpu_pool.avail, GFP_KERNEL))
>> + return -ENOMEM;
>> +
>> + mutex_init(&ne_cpu_pool.mutex);
>> +
>> + rc = cpulist_parse(ne_cpus, ne_cpu_pool.avail);
>> + if (rc < 0) {
>> + pr_err_ratelimited(NE "Error in cpulist parse [rc=%d]\n", rc);
> Again, drop all ratelimited stuff please.

Updated to pr_err().

Thank you.

Andra