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Subject[PATCH 4/5] x86/intel_rdt: Add diagnostics when writing the cpus file
Date
From: Tony Luck <tony.luck@intel.com>

Can't add a cpu to a monitor group unless it belongs to parent
group. Can't delete cpus from the default group.

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index c54189a1b54e..8b851ae601df 100644
--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -241,8 +241,11 @@ static int cpus_mon_write(struct rdtgroup *rdtgrp, cpumask_var_t newmask,

/* Check whether cpus belong to parent ctrl group */
cpumask_andnot(tmpmask, newmask, &prgrp->cpu_mask);
- if (cpumask_weight(tmpmask))
+ if (cpumask_weight(tmpmask)) {
+ seq_buf_puts(&last_cmd_status,
+ "can only add CPUs to mongroup that belong to parent\n");
return -EINVAL;
+ }

/* Check whether cpus are dropped from this group */
cpumask_andnot(tmpmask, &rdtgrp->cpu_mask, newmask);
@@ -294,8 +297,11 @@ static int cpus_ctrl_write(struct rdtgroup *rdtgrp, cpumask_var_t newmask,
cpumask_andnot(tmpmask, &rdtgrp->cpu_mask, newmask);
if (cpumask_weight(tmpmask)) {
/* Can't drop from default group */
- if (rdtgrp == &rdtgroup_default)
+ if (rdtgrp == &rdtgroup_default) {
+ seq_buf_puts(&last_cmd_status,
+ "Can't drop CPUs from default group\n");
return -EINVAL;
+ }

/* Give any dropped cpus to rdtgroup_default */
cpumask_or(&rdtgroup_default.cpu_mask,
@@ -360,8 +366,10 @@ static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of,
}

rdtgrp = rdtgroup_kn_lock_live(of->kn);
+ seq_buf_clear(&last_cmd_status);
if (!rdtgrp) {
ret = -ENOENT;
+ seq_buf_puts(&last_cmd_status, "directory was removed\n");
goto unlock;
}

@@ -370,13 +378,16 @@ static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of,
else
ret = cpumask_parse(buf, newmask);

- if (ret)
+ if (ret) {
+ seq_buf_puts(&last_cmd_status, "bad cpu list/mask\n");
goto unlock;
+ }

/* check that user didn't specify any offline cpus */
cpumask_andnot(tmpmask, newmask, cpu_online_mask);
if (cpumask_weight(tmpmask)) {
ret = -EINVAL;
+ seq_buf_puts(&last_cmd_status, "can only assign online cpus\n");
goto unlock;
}

--
2.11.0
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