[PATCH v3 1/2] x86/resctrl: Pass domain to target CPU

Tony Luck
2024-02-22T18:50:46Z

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.

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
arch/x86/kernel/cpu/resctrl/internal.h | 1 +
arch/x86/kernel/cpu/resctrl/core.c | 18 ++++------
arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 40 +++++------------------
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 14 +++-----
4 files changed, 21 insertions(+), 52 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index c99f26ebe7a6..c30d7697b431 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -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;
};
diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 83e40341583e..8d378fc7a50b 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -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);
diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
index 7997b47743a2..a3a0fd80daa8 100644
--- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
+++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
@@ -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;
}

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 011e17efb1a6..da4f13db4161 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -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;
}

--
2.43.0