On Tue, 2015-10-27 at 13:26 -0500, Nathan Fontenot wrote:
> Add the ability to dlpar remove CPUs via hotplug rtas events, either by
> specifying the drc-index of the CPU to remove or providing a count of cpus
> to remove.
>
> diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c
> b/arch/powerpc/platforms/pseries/hotplug-cpu.c
> index f080e81..635f0ba 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
> @@ -570,6 +571,143 @@ static ssize_t dlpar_cpu_remove(struct device_node *dn,
> u32 drc_index)
> return 0;
> }
>
> +static struct device_node *cpu_drc_index_to_dn(u32 drc_index)
> +{
> + struct device_node *dn;
> + u32 my_index;
> + int rc;
> +
> + for_each_node_by_type(dn, "cpu") {
> + rc = of_property_read_u32(dn, "ibm,my-drc-index", &my_index);
> + if (rc)
> + continue;
> +
> + if (my_index == drc_index)
> + break;
> + }
> +
> + return dn;
> +}
> +
> +static int dlpar_cpu_remove_by_index(u32 drc_index)
> +{
> + struct device_node *dn;
> + int rc;
> +
> + dn = cpu_drc_index_to_dn(drc_index);
> + if (!dn)
> + return -ENODEV;
> +
> + rc = dlpar_cpu_remove(dn, drc_index);
> + of_node_put(dn);
Does dlpar_cpu_remove() work when you still hold a reference to the dn?
It looks like dlpar_detach_node() does an of_node_put() also.
> + return rc;
> +}
> +
> +static u32 *dlpar_cpus_to_remove(int cpus_to_remove)
> +{
> + struct device_node *dn;
> + u32 *cpu_drcs;
> + int cpus_found = 0;
> + int i, rc;
> +
> + cpu_drcs = kcalloc(cpus_to_remove, sizeof(*cpu_drcs), GFP_KERNEL);
> + if (!cpu_drcs)
> + return NULL;
> +
> + i = 0;
> + for_each_node_by_type(dn, "cpu") {
> + cpus_found++;
> +
> + if (cpus_found > cpus_to_remove) {
> + of_node_put(dn);
> + break;
> + }
> +
> + rc = of_property_read_u32(dn, "ibm,my-drc-index",
> + &cpu_drcs[i++]);
> + if (rc) {
> + of_node_put(dn);
> + break;
I'm not sure about the logic here with cpus_found and i. If you break here
cpus_found will be 1, but you found zero, which seems odd.
If instead you delayed the increment of i:
rc = of_property_read_u32(dn, "ibm,my-drc-index",
&cpu_drcs[i]);
if (rc) {
of_node_put(dn);
break;
}
i++;
}
Then i would equal the number of cpus found at all times. If you need to count
one more in the if below you can just do that there.
> +
> + /* We want to find cpus_to_remove + 1 CPUs to ensure we do not
> + * remove the last CPU.
> + */
> + if (cpus_found <= cpus_to_remove) {
> + pr_warn("Failed to find enough CPUs (%d of %d) to remove\n",
> + cpus_found, cpus_to_remove);
> + kfree(cpu_drcs);
> + cpu_drcs = NULL;
> + }
On my two cpu system when I do "cpu remove count 1" this always says:
pseries-hotplug-cpu: Failed to find enough CPUs (1 of 1) to remove
Which confuses me.
I suspect that's because I actually have one cpu *node*, which appears to Linux
as two cpus (due to SMT). So I think it's working as expected, but it's not
very clear from a user's perspective.
cheers
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