intel_pstate: Do not call wrmsrl_on_cpu() with disabled interrupts

After commit a4675fbc4a7a (cpufreq: intel_pstate: Replace timers with
utilization update callbacks) wrmsrl_on_cpu() cannot be called in the
intel_pstate_adjust_busy_pstate() path as that is executed with
disabled interrupts.  However, atom_set_pstate() called from there
via intel_pstate_set_pstate() uses wrmsrl_on_cpu() to update the
IA32_PERF_CTL MSR which triggers the WARN_ON_ONCE() in
smp_call_function_single().

The reason why wrmsrl_on_cpu() is used by atom_set_pstate() is
because intel_pstate_set_pstate() calling it is also invoked during
the initialization and cleanup of the driver and in those cases it is
not guaranteed to be run on the CPU that is being updated.  However,
in the case when intel_pstate_set_pstate() is called by
intel_pstate_adjust_busy_pstate(), wrmsrl() can be used to update
the register safely.  Moreover, intel_pstate_set_pstate() already
contains code that only is executed if the function is called by
intel_pstate_adjust_busy_pstate() and there is a special argument
passed to it because of that.

To fix the problem at hand, rearrange the code taking the above
observations into account.

First, replace the ->set() callback in struct pstate_funcs with a
->get_val() one that will return the value to be written to the
IA32_PERF_CTL MSR without updating the register.

Second, split intel_pstate_set_pstate() into two functions,
intel_pstate_update_pstate() to be called by
intel_pstate_adjust_busy_pstate() that will contain all of the
intel_pstate_set_pstate() code which only needs to be executed in
that case and will use wrmsrl() to update the MSR (after obtaining
the value to write to it from the ->get_val() callback), and
intel_pstate_set_min_pstate() to be invoked during the
initialization and cleanup that will set the P-state to the
minimum one and will update the MSR using wrmsrl_on_cpu().

Finally, move the code shared between intel_pstate_update_pstate()
and intel_pstate_set_min_pstate() to a new static inline function
intel_pstate_record_pstate() and make them both call it.

Of course, that unifies the handling of the IA32_PERF_CTL MSR writes
between Atom and Core.

Fixes: a4675fbc4a7a (cpufreq: intel_pstate: Replace timers with utilization update callbacks)
Reported-and-tested-by: Josh Boyer <jwboyer@fedoraproject.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/intel_pstate.c

@@ -134,7 +134,7 @@ struct pstate_funcs {
 	int (*get_min)(void);
 	int (*get_turbo)(void);
 	int (*get_scaling)(void);
-	void (*set)(struct cpudata*, int pstate);
+	u64 (*get_val)(struct cpudata*, int pstate);
 	void (*get_vid)(struct cpudata *);
 	int32_t (*get_target_pstate)(struct cpudata *);
 };
@@ -565,7 +565,7 @@ static int atom_get_turbo_pstate(void)
 	return value & 0x7F;
 }
 
-static void atom_set_pstate(struct cpudata *cpudata, int pstate)
+static u64 atom_get_val(struct cpudata *cpudata, int pstate)
 {
 	u64 val;
 	int32_t vid_fp;
@@ -585,9 +585,7 @@ static void atom_set_pstate(struct cpudata *cpudata, int pstate)
 	if (pstate > cpudata->pstate.max_pstate)
 		vid = cpudata->vid.turbo;
 
-	val |= vid;
-
-	wrmsrl_on_cpu(cpudata->cpu, MSR_IA32_PERF_CTL, val);
+	return val | vid;
 }
 
 static int silvermont_get_scaling(void)
@@ -711,7 +709,7 @@ static inline int core_get_scaling(void)
 	return 100000;
 }
 
-static void core_set_pstate(struct cpudata *cpudata, int pstate)
+static u64 core_get_val(struct cpudata *cpudata, int pstate)
 {
 	u64 val;
 
@@ -719,7 +717,7 @@ static void core_set_pstate(struct cpudata *cpudata, int pstate)
 	if (limits->no_turbo && !limits->turbo_disabled)
 		val |= (u64)1 << 32;
 
-	wrmsrl(MSR_IA32_PERF_CTL, val);
+	return val;
 }
 
 static int knl_get_turbo_pstate(void)
@@ -750,7 +748,7 @@ static struct cpu_defaults core_params = {
 		.get_min = core_get_min_pstate,
 		.get_turbo = core_get_turbo_pstate,
 		.get_scaling = core_get_scaling,
-		.set = core_set_pstate,
+		.get_val = core_get_val,
 		.get_target_pstate = get_target_pstate_use_performance,
 	},
 };
@@ -769,7 +767,7 @@ static struct cpu_defaults silvermont_params = {
 		.get_max_physical = atom_get_max_pstate,
 		.get_min = atom_get_min_pstate,
 		.get_turbo = atom_get_turbo_pstate,
-		.set = atom_set_pstate,
+		.get_val = atom_get_val,
 		.get_scaling = silvermont_get_scaling,
 		.get_vid = atom_get_vid,
 		.get_target_pstate = get_target_pstate_use_cpu_load,
@@ -790,7 +788,7 @@ static struct cpu_defaults airmont_params = {
 		.get_max_physical = atom_get_max_pstate,
 		.get_min = atom_get_min_pstate,
 		.get_turbo = atom_get_turbo_pstate,
-		.set = atom_set_pstate,
+		.get_val = atom_get_val,
 		.get_scaling = airmont_get_scaling,
 		.get_vid = atom_get_vid,
 		.get_target_pstate = get_target_pstate_use_cpu_load,
@@ -812,7 +810,7 @@ static struct cpu_defaults knl_params = {
 		.get_min = core_get_min_pstate,
 		.get_turbo = knl_get_turbo_pstate,
 		.get_scaling = core_get_scaling,
-		.set = core_set_pstate,
+		.get_val = core_get_val,
 		.get_target_pstate = get_target_pstate_use_performance,
 	},
 };
@@ -839,25 +837,24 @@ static void intel_pstate_get_min_max(struct cpudata *cpu, int *min, int *max)
 	*min = clamp_t(int, min_perf, cpu->pstate.min_pstate, max_perf);
 }
 
-static void intel_pstate_set_pstate(struct cpudata *cpu, int pstate, bool force)
+static inline void intel_pstate_record_pstate(struct cpudata *cpu, int pstate)
 {
-	int max_perf, min_perf;
-
-	if (force) {
-		update_turbo_state();
-
-		intel_pstate_get_min_max(cpu, &min_perf, &max_perf);
-
-		pstate = clamp_t(int, pstate, min_perf, max_perf);
-
-		if (pstate == cpu->pstate.current_pstate)
-			return;
-	}
 	trace_cpu_frequency(pstate * cpu->pstate.scaling, cpu->cpu);
-
 	cpu->pstate.current_pstate = pstate;
+}
 
-	pstate_funcs.set(cpu, pstate);
+static void intel_pstate_set_min_pstate(struct cpudata *cpu)
+{
+	int pstate = cpu->pstate.min_pstate;
+
+	intel_pstate_record_pstate(cpu, pstate);
+	/*
+	 * Generally, there is no guarantee that this code will always run on
+	 * the CPU being updated, so force the register update to run on the
+	 * right CPU.
+	 */
+	wrmsrl_on_cpu(cpu->cpu, MSR_IA32_PERF_CTL,
+		      pstate_funcs.get_val(cpu, pstate));
 }
 
 static void intel_pstate_get_cpu_pstates(struct cpudata *cpu)
@@ -870,7 +867,8 @@ static void intel_pstate_get_cpu_pstates(struct cpudata *cpu)
 
 	if (pstate_funcs.get_vid)
 		pstate_funcs.get_vid(cpu);
-	intel_pstate_set_pstate(cpu, cpu->pstate.min_pstate, false);
+
+	intel_pstate_set_min_pstate(cpu);
 }
 
 static inline void intel_pstate_calc_busy(struct cpudata *cpu)
@@ -997,6 +995,21 @@ static inline int32_t get_target_pstate_use_performance(struct cpudata *cpu)
 	return cpu->pstate.current_pstate - pid_calc(&cpu->pid, core_busy);
 }
 
+static inline void intel_pstate_update_pstate(struct cpudata *cpu, int pstate)
+{
+	int max_perf, min_perf;
+
+	update_turbo_state();
+
+	intel_pstate_get_min_max(cpu, &min_perf, &max_perf);
+	pstate = clamp_t(int, pstate, min_perf, max_perf);
+	if (pstate == cpu->pstate.current_pstate)
+		return;
+
+	intel_pstate_record_pstate(cpu, pstate);
+	wrmsrl(MSR_IA32_PERF_CTL, pstate_funcs.get_val(cpu, pstate));
+}
+
 static inline void intel_pstate_adjust_busy_pstate(struct cpudata *cpu)
 {
 	int from, target_pstate;
@@ -1006,7 +1019,7 @@ static inline void intel_pstate_adjust_busy_pstate(struct cpudata *cpu)
 
 	target_pstate = pstate_funcs.get_target_pstate(cpu);
 
-	intel_pstate_set_pstate(cpu, target_pstate, true);
+	intel_pstate_update_pstate(cpu, target_pstate);
 
 	sample = &cpu->sample;
 	trace_pstate_sample(fp_toint(sample->core_pct_busy),
@@ -1180,7 +1193,7 @@ static void intel_pstate_stop_cpu(struct cpufreq_policy *policy)
 	if (hwp_active)
 		return;
 
-	intel_pstate_set_pstate(cpu, cpu->pstate.min_pstate, false);
+	intel_pstate_set_min_pstate(cpu);
 }
 
 static int intel_pstate_cpu_init(struct cpufreq_policy *policy)
@@ -1255,7 +1268,7 @@ static void copy_cpu_funcs(struct pstate_funcs *funcs)
 	pstate_funcs.get_min   = funcs->get_min;
 	pstate_funcs.get_turbo = funcs->get_turbo;
 	pstate_funcs.get_scaling = funcs->get_scaling;
-	pstate_funcs.set       = funcs->set;
+	pstate_funcs.get_val   = funcs->get_val;
 	pstate_funcs.get_vid   = funcs->get_vid;
 	pstate_funcs.get_target_pstate = funcs->get_target_pstate;