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Subject[PATCH 1/5] x86/intel_rdt: Add framework for better RDT UI diagnostics
Date
From: Tony Luck <tony.luck@intel.com>

Commands are given to the resctrl file system by making/removing
directories, or by writing to files. When something goes wrong
the user is generally left wondering why they got:

bash: echo: write error: Invalid argument

Add a new file "last_cmd_status" to the "info" directory that
will give the user some better clues on what went wrong.

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
arch/x86/kernel/cpu/intel_rdt.h | 6 ++++++
arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 33 ++++++++++++++++++++++++++++++++
2 files changed, 39 insertions(+)

diff --git a/arch/x86/kernel/cpu/intel_rdt.h b/arch/x86/kernel/cpu/intel_rdt.h
index ebaddaeef023..afba509ac164 100644
--- a/arch/x86/kernel/cpu/intel_rdt.h
+++ b/arch/x86/kernel/cpu/intel_rdt.h
@@ -2,6 +2,7 @@
#define _ASM_X86_INTEL_RDT_H

#include <linux/sched.h>
+#include <linux/seq_buf.h>
#include <linux/kernfs.h>
#include <linux/jump_label.h>

@@ -30,6 +31,8 @@

DECLARE_STATIC_KEY_FALSE(rdt_enable_key);

+extern struct seq_buf last_cmd_status;
+
/**
* struct mon_evt - Entry in the event list of a resource
* @evtid: event id
@@ -126,12 +129,15 @@ struct rdtgroup {
#define RFTYPE_BASE BIT(1)
#define RF_CTRLSHIFT 4
#define RF_MONSHIFT 5
+#define RF_TOPSHIFT 6
#define RFTYPE_CTRL BIT(RF_CTRLSHIFT)
#define RFTYPE_MON BIT(RF_MONSHIFT)
+#define RFTYPE_TOP BIT(RF_TOPSHIFT)
#define RFTYPE_RES_CACHE BIT(8)
#define RFTYPE_RES_MB BIT(9)
#define RF_CTRL_INFO (RFTYPE_INFO | RFTYPE_CTRL)
#define RF_MON_INFO (RFTYPE_INFO | RFTYPE_MON)
+#define RF_TOP_INFO (RFTYPE_INFO | RFTYPE_TOP)
#define RF_CTRL_BASE (RFTYPE_BASE | RFTYPE_CTRL)

/* List of all resource groups */
diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index a869d4a073c5..6a2cd89fa9de 100644
--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -51,6 +51,9 @@ static struct kernfs_node *kn_mongrp;
/* Kernel fs node for "mon_data" directory under root */
static struct kernfs_node *kn_mondata;

+struct seq_buf last_cmd_status;
+static char last_cmd_status_buf[512];
+
/*
* Trivial allocator for CLOSIDs. Since h/w only supports a small number,
* we can keep a bitmap of free CLOSIDs in a single integer.
@@ -569,6 +572,21 @@ static int rdtgroup_tasks_show(struct kernfs_open_file *of,
return ret;
}

+static int rdt_last_cmd_status_show(struct kernfs_open_file *of,
+ struct seq_file *seq, void *v)
+{
+ int len;
+
+ mutex_lock(&rdtgroup_mutex);
+ len = seq_buf_used(&last_cmd_status);
+ if (len)
+ seq_printf(seq, "%.*s", len, last_cmd_status_buf);
+ else
+ seq_puts(seq, "ok\n");
+ mutex_unlock(&rdtgroup_mutex);
+ return 0;
+}
+
static int rdt_num_closids_show(struct kernfs_open_file *of,
struct seq_file *seq, void *v)
{
@@ -686,6 +704,13 @@ static ssize_t max_threshold_occ_write(struct kernfs_open_file *of,
/* rdtgroup information files for one cache resource. */
static struct rftype res_common_files[] = {
{
+ .name = "last_cmd_status",
+ .mode = 0444,
+ .kf_ops = &rdtgroup_kf_single_ops,
+ .seq_show = rdt_last_cmd_status_show,
+ .fflags = RF_TOP_INFO,
+ },
+ {
.name = "num_closids",
.mode = 0444,
.kf_ops = &rdtgroup_kf_single_ops,
@@ -855,6 +880,10 @@ static int rdtgroup_create_info_dir(struct kernfs_node *parent_kn)
return PTR_ERR(kn_info);
kernfs_get(kn_info);

+ ret = rdtgroup_add_files(kn_info, RF_TOP_INFO);
+ if (ret)
+ goto out_destroy;
+
for_each_alloc_enabled_rdt_resource(r) {
fflags = r->fflags | RF_CTRL_INFO;
ret = rdtgroup_mkdir_info_resdir(r, r->name, fflags);
@@ -1156,6 +1185,7 @@ static struct dentry *rdt_mount(struct file_system_type *fs_type,
out_cdp:
cdp_disable();
out:
+ seq_buf_clear(&last_cmd_status);
mutex_unlock(&rdtgroup_mutex);

return dentry;
@@ -1902,6 +1932,9 @@ int __init rdtgroup_init(void)
{
int ret = 0;

+ seq_buf_init(&last_cmd_status, last_cmd_status_buf,
+ sizeof(last_cmd_status_buf));
+
ret = rdtgroup_setup_root();
if (ret)
return ret;
--
2.11.0
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