Messages in this thread Patch in this message | | | Date | Wed, 1 Mar 2017 16:24:41 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH 4/8] x86/intel_rct/mba: Add MBA structures and initialize MBA |
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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
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