On Fri, 17 Feb 2017, Vikas Shivappa wrote:
--- a/arch/x86/include/asm/intel_rdt.h
+++ b/arch/x86/include/asm/intel_rdt.h
@@ -11,6 +11,9 @@
#define IA32_L3_QOS_CFG 0xc81
#define IA32_L3_CBM_BASE 0xc90
#define IA32_L2_CBM_BASE 0xd10
+#define IA32_MBA_THRTL_BASE 0xd50
+#define MAX_MBA_THRTL 100u
+#define MBA_IS_LINEAR 0x4
I have a hard time to figure out how the latter two constants are related
to this list of registers. MBA_IS_LINEAR is used to check the CPUID bit and
MAX_MBA_THRTL is obviously a pure software constant because with a
non-linear scale the maximum value is not 100.
Just slapping defines to random places is equally bad as using hard coded
constants.
+/*
+ * rdt_get_mb_table() - get a mapping of b/w percentage values
+ * exposed to user interface and the h/w understandable delay values.
+ *
+ * The non-linear delay values have the granularity of power of two
+ * and also the h/w does not guarantee a curve for configured delay
+ * values vs. actual b/w throttled.
+ * Hence we need a mapping that is pre caliberated for user to express
+ * the b/w in terms of any sensible number.
... calibrated so the user can express the bandwidth as a percentage value.
+static inline int rdt_get_mb_table(struct rdt_resource *r)
+{
+ /*
+ * There are no Intel SKUs as of now to support non-linear delay.
+ */
+ r->mb_map = NULL;
What's the point of setting this to NULL?
Also it would be helpful to emit log info here so people don't have to
start digging around.
pr_info("Bandwidth map not implemented for ....", ... model);
+
+ return -ENODEV;
Returning -ENODEV to a function which just returns a boolean value is
pointless.
static void rdt_get_cache_config(int idx, struct rdt_resource *r)
{
union cpuid_0x10_1_eax eax;
@@ -184,9 +237,8 @@ static inline bool get_rdt_resources(void)
ret = true;
}
- if (boot_cpu_has(X86_FEATURE_MBA)) {
- ret = true;
- }
+ if (boot_cpu_has(X86_FEATURE_MBA))
+ ret = rdt_get_mem_config(&rdt_resources_all[RDT_RESOURCE_MBA]);
Groan. When rdt_get_mem_config() returns false (because the map is not
implemented), then the whole function returns false and CAT is disabled.
+static int domain_setup_ctrlval(struct rdt_resource *r, struct rdt_domain *d)
+{
+ int i;
+
+ d->ctrl_val = kmalloc_array(r->num_closid,
+ sizeof(*d->ctrl_val), GFP_KERNEL);
+ if (!d->ctrl_val)
+ return -ENOMEM;
+
+ /*
+ * Initialize the Control MSRs to having no control.
+ * For Cache Allocation: Set all bits in cbm
+ * For Memory Allocation: Set b/w requested to 100
+ */
+ for (i = 0; i < r->num_closid; i++) {
+ int idx = cbm_idx(r, i);
+
+ d->ctrl_val[i] = r->default_ctrl;
+ wrmsrl(r->msr_base + idx, d->ctrl_val[i]);
+ }
So if you use a local pointer for that, this whole mess becomes readable.
static int domain_setup_ctrlval(struct rdt_resource *r, struct rdt_domain *d)
{
u32 *p;
int i;
p = kmalloc_array(r->num_closid, sizeof(*d->ctrl_val), GFP_KERNEL);
if (!p)
return -ENOMEM;
d->ctrl_val = p;
/* Initialize the Control MSRs to the default value */
for (i = 0; i < r->num_closid; i++, p++) {
int idx = cbm_idx(r, i);
*p = r->default_ctrl;
wrmsrl(r->msr_base + idx, *p);
}
+
+ return 0;
+}
static void domain_add_cpu(int cpu, struct rdt_resource *r)
{
- int i, id = get_cache_id(cpu, r->cache_level);
+ int id = get_cache_id(cpu, r->cache_level), ret;
Bah. If you have the same type in one line, then please move the
uninitialized variables to the front.
int ret, id = get_cache_id(cpu, r->cache_level);
But a s/i/ret/ would have been to simple and kept the code readable.
@@ -298,19 +374,12 @@ static void domain_add_cpu(int cpu, struct rdt_resource
*r)
d->id = id;
- d->ctrl_val = kmalloc_array(r->num_closid, sizeof(*d->ctrl_val),
GFP_KERNEL);
- if (!d->ctrl_val) {
+ ret = domain_setup_ctrlval(r, d);
+ if (ret) {
kfree(d);
return;
}
What's the point of this 'ret' variable if the function is void?
if (domain_setup_ctrlval(r, d)) {
kfree(d);
return;
}
would have been to easy to read, right?
