x86/intel_rdt: Add diagnostics when writing the schemata file

Save helpful descriptions of what went wrong when writing a
schemata file.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Vikas Shivappa <vikas.shivappa@intel.com>
Cc: Boris Petkov <bp@suse.de>
Cc: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lkml.kernel.org/r/9d6cef757dc88639c8ab47f1e7bc1b081a84bb88.1506382469.git.tony.luck@intel.com

1 files changed, 38 insertions, 11 deletions

diff --git a/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c b/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c
index f6ea94f8954a..f29b4c21e7d4 100644
--- a/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c
+++ b/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c
@@ -42,15 +42,22 @@ static bool bw_validate(char *buf, unsigned long *data, struct rdt_resource *r)
         /*
          * Only linear delay values is supported for current Intel SKUs.
          */
-        if (!r->membw.delay_linear)
+        if (!r->membw.delay_linear) {
+                rdt_last_cmd_puts("No support for non-linear MB domains\n");
                 return false;
+        }
 
         ret = kstrtoul(buf, 10, &bw);
-        if (ret)
+        if (ret) {
+                rdt_last_cmd_printf("Non-decimal digit in MB value %s\n", buf);
                 return false;
+        }
 
-        if (bw < r->membw.min_bw || bw > r->default_ctrl)
+        if (bw < r->membw.min_bw || bw > r->default_ctrl) {
+                rdt_last_cmd_printf("MB value %ld out of range [%d,%d]\n", bw,
+                                    r->membw.min_bw, r->default_ctrl);
                 return false;
+        }
 
         *data = roundup(bw, (unsigned long)r->membw.bw_gran);
         return true;
@@ -60,8 +67,10 @@ int parse_bw(char *buf, struct rdt_resource *r, struct rdt_domain *d)
 {
         unsigned long data;
 
-        if (d->have_new_ctrl)
+        if (d->have_new_ctrl) {
+                rdt_last_cmd_printf("duplicate domain %d\n", d->id);
                 return -EINVAL;
+        }
 
         if (!bw_validate(buf, &data, r))
                 return -EINVAL;
@@ -84,20 +93,29 @@ static bool cbm_validate(char *buf, unsigned long *data, struct rdt_resource *r)
         int ret;
 
         ret = kstrtoul(buf, 16, &val);
-        if (ret)
+        if (ret) {
+                rdt_last_cmd_printf("non-hex character in mask %s\n", buf);
                 return false;
+        }
 
-        if (val == 0 || val > r->default_ctrl)
+        if (val == 0 || val > r->default_ctrl) {
+                rdt_last_cmd_puts("mask out of range\n");
                 return false;
+        }
 
         first_bit = find_first_bit(&val, cbm_len);
         zero_bit = find_next_zero_bit(&val, cbm_len, first_bit);
 
-        if (find_next_bit(&val, cbm_len, zero_bit) < cbm_len)
+        if (find_next_bit(&val, cbm_len, zero_bit) < cbm_len) {
+                rdt_last_cmd_printf("mask %lx has non-consecutive 1-bits\n", val);
                 return false;
+        }
 
-        if ((zero_bit - first_bit) < r->cache.min_cbm_bits)
+        if ((zero_bit - first_bit) < r->cache.min_cbm_bits) {
+                rdt_last_cmd_printf("Need at least %d bits in mask\n",
+                                    r->cache.min_cbm_bits);
                 return false;
+        }
 
         *data = val;
         return true;
@@ -111,8 +129,10 @@ int parse_cbm(char *buf, struct rdt_resource *r, struct rdt_domain *d)
 {
         unsigned long data;
 
-        if (d->have_new_ctrl)
+        if (d->have_new_ctrl) {
+                rdt_last_cmd_printf("duplicate domain %d\n", d->id);
                 return -EINVAL;
+        }
 
         if(!cbm_validate(buf, &data, r))
                 return -EINVAL;
@@ -139,8 +159,10 @@ next:
                 return 0;
         dom = strsep(&line, ";");
         id = strsep(&dom, "=");
-        if (!dom || kstrtoul(id, 10, &dom_id))
+        if (!dom || kstrtoul(id, 10, &dom_id)) {
+                rdt_last_cmd_puts("Missing '=' or non-numeric domain\n");
                 return -EINVAL;
+        }
         dom = strim(dom);
         list_for_each_entry(d, &r->domains, list) {
                 if (d->id == dom_id) {
@@ -196,6 +218,7 @@ static int rdtgroup_parse_resource(char *resname, char *tok, int closid)
                 if (!strcmp(resname, r->name) && closid < r->num_closid)
                         return parse_line(tok, r);
         }
+        rdt_last_cmd_printf("unknown/unsupported resource name '%s'\n", resname);
         return -EINVAL;
 }
 
@@ -209,8 +232,10 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
         int closid, ret = 0;
 
         /* Valid input requires a trailing newline */
-        if (nbytes == 0 || buf[nbytes - 1] != '\n')
+        if (nbytes == 0 || buf[nbytes - 1] != '\n') {
+                seq_buf_puts(&last_cmd_status, "no trailing newline\n");
                 return -EINVAL;
+        }
         buf[nbytes - 1] = '\0';
 
         rdtgrp = rdtgroup_kn_lock_live(of->kn);
@@ -218,6 +243,7 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
                 rdtgroup_kn_unlock(of->kn);
                 return -ENOENT;
         }
+        rdt_last_cmd_clear();
 
         closid = rdtgrp->closid;
 
@@ -229,6 +255,7 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
         while ((tok = strsep(&buf, "\n")) != NULL) {
                 resname = strim(strsep(&tok, ":"));
                 if (!tok) {
+                        rdt_last_cmd_puts("Missing ':'\n");
                         ret = -EINVAL;
                         goto out;
                 }