Hi Tony,
On 2/22/2024 10:50 AM, Tony Luck wrote:
> reset_all_ctrls() and resctrl_arch_update_domains() use on_each_cpu_mask()
> to call rdt_ctrl_update() on potentially one CPU from each domain.
>
> But this means rdt_ctrl_update() needs to figure out which domain to apply
> changes to. Doing so requires a search of all domains in a resource,
> which can only be done safely if cpus_lock is held. Both callers do
> hold this lock, but there isn't a way for a function called on another
> CPU via IPI to verify this.
>
> Commit c0d848fcb09d ("x86/resctrl: Remove lockdep annotation that triggers
> false positive") removed the incorrect assertions.
>
> Adding the target domain to the msr_param structure, and calling
> for each domain separately using smp_call_function_single() means
> that rdt_ctrl_update() doesn't need to search for the domain. Thus
> get_domain_from_cpu() can safely assert that the cpus_lock is held since
> the remaining callers do not use IPI.
Please stick to the imperative tone. Something like (please feel free to
improve):
Add the target domain to the msr_param structure and call
rdt_ctrl_update() for each domain separately using
smp_call_function_single(). This means that rdt_ctrl_update()
doesn't need to search for the domain and get_domain_from_cpu()
can safely assert that the cpus_lock is held since
the remaining callers do not use IPI.
..
> @@ -463,6 +457,8 @@ static int domain_setup_ctrlval(struct rdt_resource *r, struct rdt_domain *d)
> hw_dom->ctrl_val = dc;
> setup_default_ctrlval(r, dc);
>
> + m.res = r;
This belongs in the next patch.
> + m.dom = d;
> m.low = 0;
> m.high = hw_res->num_closid;
> hw_res->msr_update(d, &m, r);
The rest looks good to me and I think it is a good improvement.
Thank you very much.
Reinette
@@ -383,6 +383,7 @@ static inline struct rdt_hw_domain *resctrl_to_arch_dom(struct rdt_domain *r)
*/
struct msr_param {
struct rdt_resource *res;
+ struct rdt_domain *dom;
u32 low;
u32 high;
};
@@ -362,6 +362,8 @@ struct rdt_domain *get_domain_from_cpu(int cpu, struct rdt_resource *r)
{
struct rdt_domain *d;
+ lockdep_assert_cpus_held();
+
list_for_each_entry(d, &r->domains, list) {
/* Find the domain that contains this CPU */
if (cpumask_test_cpu(cpu, &d->cpu_mask))
@@ -378,19 +380,11 @@ u32 resctrl_arch_get_num_closid(struct rdt_resource *r)
void rdt_ctrl_update(void *arg)
{
+ struct rdt_hw_resource *hw_res;
struct msr_param *m = arg;
- struct rdt_hw_resource *hw_res = resctrl_to_arch_res(m->res);
- struct rdt_resource *r = m->res;
- int cpu = smp_processor_id();
- struct rdt_domain *d;
- d = get_domain_from_cpu(cpu, r);
- if (d) {
- hw_res->msr_update(d, m, r);
- return;
- }
- pr_warn_once("cpu %d not found in any domain for resource %s\n",
- cpu, r->name);
+ hw_res = resctrl_to_arch_res(m->res);
+ hw_res->msr_update(m->dom, m, m->res);
}
/*
@@ -463,6 +457,8 @@ static int domain_setup_ctrlval(struct rdt_resource *r, struct rdt_domain *d)
hw_dom->ctrl_val = dc;
setup_default_ctrlval(r, dc);
+ m.res = r;
+ m.dom = d;
m.low = 0;
m.high = hw_res->num_closid;
hw_res->msr_update(d, &m, r);
@@ -272,22 +272,6 @@ static u32 get_config_index(u32 closid, enum resctrl_conf_type type)
}
}
-static bool apply_config(struct rdt_hw_domain *hw_dom,
- struct resctrl_staged_config *cfg, u32 idx,
- cpumask_var_t cpu_mask)
-{
- struct rdt_domain *dom = &hw_dom->d_resctrl;
-
- if (cfg->new_ctrl != hw_dom->ctrl_val[idx]) {
- cpumask_set_cpu(cpumask_any(&dom->cpu_mask), cpu_mask);
- hw_dom->ctrl_val[idx] = cfg->new_ctrl;
-
- return true;
- }
-
- return false;
-}
-
int resctrl_arch_update_one(struct rdt_resource *r, struct rdt_domain *d,
u32 closid, enum resctrl_conf_type t, u32 cfg_val)
{
@@ -302,6 +286,7 @@ int resctrl_arch_update_one(struct rdt_resource *r, struct rdt_domain *d,
hw_dom->ctrl_val[idx] = cfg_val;
msr_param.res = r;
+ msr_param.dom = d;
msr_param.low = idx;
msr_param.high = idx + 1;
hw_res->msr_update(d, &msr_param, r);
@@ -315,27 +300,27 @@ int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid)
struct rdt_hw_domain *hw_dom;
struct msr_param msr_param;
enum resctrl_conf_type t;
- cpumask_var_t cpu_mask;
struct rdt_domain *d;
+ int cpu;
u32 idx;
/* Walking r->domains, ensure it can't race with cpuhp */
lockdep_assert_cpus_held();
- if (!zalloc_cpumask_var(&cpu_mask, GFP_KERNEL))
- return -ENOMEM;
-
- msr_param.res = NULL;
list_for_each_entry(d, &r->domains, list) {
hw_dom = resctrl_to_arch_dom(d);
+ msr_param.res = NULL;
+ msr_param.dom = d;
for (t = 0; t < CDP_NUM_TYPES; t++) {
cfg = &hw_dom->d_resctrl.staged_config[t];
if (!cfg->have_new_ctrl)
continue;
idx = get_config_index(closid, t);
- if (!apply_config(hw_dom, cfg, idx, cpu_mask))
+ if (cfg->new_ctrl == hw_dom->ctrl_val[idx])
continue;
+ hw_dom->ctrl_val[idx] = cfg->new_ctrl;
+ cpu = cpumask_any(&d->cpu_mask);
if (!msr_param.res) {
msr_param.low = idx;
@@ -346,17 +331,10 @@ int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid)
msr_param.high = max(msr_param.high, idx + 1);
}
}
+ if (msr_param.res)
+ smp_call_function_single(cpu, rdt_ctrl_update, &msr_param, 1);
}
- if (cpumask_empty(cpu_mask))
- goto done;
-
- /* Update resource control msr on all the CPUs. */
- on_each_cpu_mask(cpu_mask, rdt_ctrl_update, &msr_param, 1);
-
-done:
- free_cpumask_var(cpu_mask);
-
return 0;
}
@@ -2813,16 +2813,13 @@ static int reset_all_ctrls(struct rdt_resource *r)
struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
struct rdt_hw_domain *hw_dom;
struct msr_param msr_param;
- cpumask_var_t cpu_mask;
struct rdt_domain *d;
+ int cpu;
int i;
/* Walking r->domains, ensure it can't race with cpuhp */
lockdep_assert_cpus_held();
- if (!zalloc_cpumask_var(&cpu_mask, GFP_KERNEL))
- return -ENOMEM;
-
msr_param.res = r;
msr_param.low = 0;
msr_param.high = hw_res->num_closid;
@@ -2834,17 +2831,14 @@ static int reset_all_ctrls(struct rdt_resource *r)
*/
list_for_each_entry(d, &r->domains, list) {
hw_dom = resctrl_to_arch_dom(d);
- cpumask_set_cpu(cpumask_any(&d->cpu_mask), cpu_mask);
+ cpu = cpumask_any(&d->cpu_mask);
for (i = 0; i < hw_res->num_closid; i++)
hw_dom->ctrl_val[i] = r->default_ctrl;
+ msr_param.dom = d;
+ smp_call_function_single(cpu, rdt_ctrl_update, &msr_param, 1);
}
- /* Update CBM on all the CPUs in cpu_mask */
- on_each_cpu_mask(cpu_mask, rdt_ctrl_update, &msr_param, 1);
-
- free_cpumask_var(cpu_mask);
-
return 0;
}