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?
Thanks,
tglx
