[CPUFREQ] cpumask: avoid playing with cpus_allowed in powernow-k8.c

cpumask: avoid playing with cpus_allowed in powernow-k8.c

It's generally a very bad idea to mug some process's cpumask: it could
legitimately and reasonably be changed by root, which could break us
(if done before our code) or them (if we restore the wrong value).

I did not replace powernowk8_target; it needs fixing, but it grabs a
mutex (so no smp_call_function_single here) but Mark points out it can
be called multiple times per second, so work_on_cpu is too heavy.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
To: cpufreq@vger.kernel.org
Acked-by: Mark Langsdorf <mark.langsdorf@amd.com>
Tested-by: Mark Langsdorf <mark.langsdorf@amd.com>
Signed-off-by: Dave Jones <davej@redhat.com>

1 files changed, 60 insertions, 58 deletions

diff --git a/arch/x86/kernel/cpu/cpufreq/powernow-k8.c b/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
index 20c7b99d7ba8..1f55547d5b30 100644
--- a/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
+++ b/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
@@ -508,41 +508,34 @@ static int core_voltage_post_transition(struct powernow_k8_data *data,
         return 0;
 }
 
-static int check_supported_cpu(unsigned int cpu)
+static void check_supported_cpu(void *_rc)
 {
-        cpumask_t oldmask;
         u32 eax, ebx, ecx, edx;
-        unsigned int rc = 0;
-
-        oldmask = current->cpus_allowed;
-        set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
+        int *rc = _rc;
 
-        if (smp_processor_id() != cpu) {
-                printk(KERN_ERR PFX "limiting to cpu %u failed\n", cpu);
-                goto out;
-        }
+        *rc = -ENODEV;
 
         if (current_cpu_data.x86_vendor != X86_VENDOR_AMD)
-                goto out;
+                return;
 
         eax = cpuid_eax(CPUID_PROCESSOR_SIGNATURE);
         if (((eax & CPUID_XFAM) != CPUID_XFAM_K8) &&
             ((eax & CPUID_XFAM) < CPUID_XFAM_10H))
-                goto out;
+                return;
 
         if ((eax & CPUID_XFAM) == CPUID_XFAM_K8) {
                 if (((eax & CPUID_USE_XFAM_XMOD) != CPUID_USE_XFAM_XMOD) ||
                     ((eax & CPUID_XMOD) > CPUID_XMOD_REV_MASK)) {
                         printk(KERN_INFO PFX
                                 "Processor cpuid %x not supported\n", eax);
-                        goto out;
+                        return;
                 }
 
                 eax = cpuid_eax(CPUID_GET_MAX_CAPABILITIES);
                 if (eax < CPUID_FREQ_VOLT_CAPABILITIES) {
                         printk(KERN_INFO PFX
                                "No frequency change capabilities detected\n");
-                        goto out;
+                        return;
                 }
 
                 cpuid(CPUID_FREQ_VOLT_CAPABILITIES, &eax, &ebx, &ecx, &edx);
@@ -550,21 +543,17 @@ static int check_supported_cpu(unsigned int cpu)
                         != P_STATE_TRANSITION_CAPABLE) {
                         printk(KERN_INFO PFX
                                 "Power state transitions not supported\n");
-                        goto out;
+                        return;
                 }
         } else { /* must be a HW Pstate capable processor */
                 cpuid(CPUID_FREQ_VOLT_CAPABILITIES, &eax, &ebx, &ecx, &edx);
                 if ((edx & USE_HW_PSTATE) == USE_HW_PSTATE)
                         cpu_family = CPU_HW_PSTATE;
                 else
-                        goto out;
+                        return;
         }
 
-        rc = 1;
-
-out:
-        set_cpus_allowed_ptr(current, &oldmask);
-        return rc;
+        *rc = 0;
 }
 
 static int check_pst_table(struct powernow_k8_data *data, struct pst_s *pst,
@@ -1247,6 +1236,32 @@ static int powernowk8_verify(struct cpufreq_policy *pol)
         return cpufreq_frequency_table_verify(pol, data->powernow_table);
 }
 
+struct init_on_cpu {
+        struct powernow_k8_data *data;
+        int rc;
+};
+
+static void __cpuinit powernowk8_cpu_init_on_cpu(void *_init_on_cpu)
+{
+        struct init_on_cpu *init_on_cpu = _init_on_cpu;
+
+        if (pending_bit_stuck()) {
+                printk(KERN_ERR PFX "failing init, change pending bit set\n");
+                init_on_cpu->rc = -ENODEV;
+                return;
+        }
+
+        if (query_current_values_with_pending_wait(init_on_cpu->data)) {
+                init_on_cpu->rc = -ENODEV;
+                return;
+        }
+
+        if (cpu_family == CPU_OPTERON)
+                fidvid_msr_init();
+
+        init_on_cpu->rc = 0;
+}
+
 /* per CPU init entry point to the driver */
 static int __cpuinit powernowk8_cpu_init(struct cpufreq_policy *pol)
 {
@@ -1254,13 +1269,14 @@ static int __cpuinit powernowk8_cpu_init(struct cpufreq_policy *pol)
                 KERN_ERR FW_BUG PFX "No compatible ACPI _PSS objects found.\n"
                 KERN_ERR FW_BUG PFX "Try again with latest BIOS.\n";
         struct powernow_k8_data *data;
-        cpumask_t oldmask;
+        struct init_on_cpu init_on_cpu;
         int rc;
 
         if (!cpu_online(pol->cpu))
                 return -ENODEV;
 
-        if (!check_supported_cpu(pol->cpu))
+        smp_call_function_single(pol->cpu, check_supported_cpu, &rc, 1);
+        if (rc)
                 return -ENODEV;
 
         data = kzalloc(sizeof(struct powernow_k8_data), GFP_KERNEL);
@@ -1300,27 +1316,12 @@ static int __cpuinit powernowk8_cpu_init(struct cpufreq_policy *pol)
                 pol->cpuinfo.transition_latency = get_transition_latency(data);
 
         /* only run on specific CPU from here on */
-        oldmask = current->cpus_allowed;
-        set_cpus_allowed_ptr(current, &cpumask_of_cpu(pol->cpu));
-
-        if (smp_processor_id() != pol->cpu) {
-                printk(KERN_ERR PFX "limiting to cpu %u failed\n", pol->cpu);
-                goto err_out_unmask;
-        }
-
-        if (pending_bit_stuck()) {
-                printk(KERN_ERR PFX "failing init, change pending bit set\n");
-                goto err_out_unmask;
-        }
-
-        if (query_current_values_with_pending_wait(data))
-                goto err_out_unmask;
-
-        if (cpu_family == CPU_OPTERON)
-                fidvid_msr_init();
-
-        /* run on any CPU again */
-        set_cpus_allowed_ptr(current, &oldmask);
+        init_on_cpu.data = data;
+        smp_call_function_single(data->cpu, powernowk8_cpu_init_on_cpu,
+                                 &init_on_cpu, 1);
+        rc = init_on_cpu.rc;
+        if (rc != 0)
+                goto err_out_exit_acpi;
 
         if (cpu_family == CPU_HW_PSTATE)
                 cpumask_copy(pol->cpus, cpumask_of(pol->cpu));
@@ -1357,8 +1358,7 @@ static int __cpuinit powernowk8_cpu_init(struct cpufreq_policy *pol)
 
         return 0;
 
-err_out_unmask:
-        set_cpus_allowed_ptr(current, &oldmask);
+err_out_exit_acpi:
         powernow_k8_cpu_exit_acpi(data);
 
 err_out:
@@ -1383,24 +1383,25 @@ static int __devexit powernowk8_cpu_exit(struct cpufreq_policy *pol)
         return 0;
 }
 
+static void query_values_on_cpu(void *_err)
+{
+        int *err = _err;
+        struct powernow_k8_data *data = __get_cpu_var(powernow_data);
+
+        *err = query_current_values_with_pending_wait(data);
+}
+
 static unsigned int powernowk8_get(unsigned int cpu)
 {
         struct powernow_k8_data *data = per_cpu(powernow_data, cpu);
-        cpumask_t oldmask = current->cpus_allowed;
         unsigned int khz = 0;
+        int err;
 
         if (!data)
                 return -EINVAL;
 
-        set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
-        if (smp_processor_id() != cpu) {
-                printk(KERN_ERR PFX
-                        "limiting to CPU %d failed in powernowk8_get\n", cpu);
-                set_cpus_allowed_ptr(current, &oldmask);
-                return 0;
-        }
-
-        if (query_current_values_with_pending_wait(data))
+        smp_call_function_single(cpu, query_values_on_cpu, &err, true);
+        if (err)
                 goto out;
 
         if (cpu_family == CPU_HW_PSTATE)
@@ -1411,7 +1412,6 @@ static unsigned int powernowk8_get(unsigned int cpu)
 
 
 out:
-        set_cpus_allowed_ptr(current, &oldmask);
         return khz;
 }
 
@@ -1437,7 +1437,9 @@ static int __cpuinit powernowk8_init(void)
         unsigned int i, supported_cpus = 0;
 
         for_each_online_cpu(i) {
-                if (check_supported_cpu(i))
+                int rc;
+                smp_call_function_single(i, check_supported_cpu, &rc, 1);
+                if (rc == 0)
                         supported_cpus++;
         }