[Xen-devel] [PATCH 2/3] xen/processor-passthru: Support vCPU != pCPU - aka dom0_max_vcpus

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

By enumerating the ACPI CPU ID - similar to how sprocessor_core
does it - we can extract those values and provide them to the
hypervisor. For this to work, we need to wean ourself off the
cpumask type macros as they are keyed to nr_cpu_ids (which in
turn is reset to cpu_online_cpus()). We convert the framework
to use a bitmap and set the ACPI ID in it instead of the APIC ID.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 drivers/xen/processor-passthru.c |  129 ++++++++++++++++++++++++++++++++------
 1 files changed, 110 insertions(+), 19 deletions(-)

diff --git a/drivers/xen/processor-passthru.c b/drivers/xen/processor-passthru.c
index abfcbe4..9ca2965 100644
--- a/drivers/xen/processor-passthru.c
+++ b/drivers/xen/processor-passthru.c
@@ -14,14 +14,6 @@
  *
  */
 
-/*
- *  Known limitations
- *
- * The driver can only handle up to  for_each_possible_cpu().
- * Meaning if you boot with dom0_max_cpus=X it will _only_ parse up to X
- * processors.
- */
-
 #include <linux/cpumask.h>
 #include <linux/cpufreq.h>
 #include <linux/kernel.h>
@@ -46,8 +38,15 @@ MODULE_PARM_DESC(off, "Inhibit the hypercall.");
 static int no_hypercall;
 module_param_named(off, no_hypercall, int, 0400);
 
-static DEFINE_MUTEX(processors_done_mutex);
-static DECLARE_BITMAP(processors_done, NR_CPUS);
+static DEFINE_MUTEX(acpi_ids_mutex);
+
+/*
+ * Don't think convert this to cpumask_var_t or use cpumask_bit - as those are
+ * keyed of cpu_present which can be less than what we want to put in
+ */
+#define NR_ACPI_CPUS NR_CPUS
+#define MAX_ACPI_BITS (BITS_TO_LONGS(NR_ACPI_CPUS))
+static unsigned long *acpi_ids_done;
 
 #define POLL_TIMER msecs_to_jiffies(5000 /* 5 sec */)
 static struct task_struct *xen_processor_thread;
@@ -249,13 +248,13 @@ static int xen_push_pxx_to_hypervisor(struct 
acpi_processor *_pr)
  * so that there is only one caller. This is so that we won't
  * race with the CPU hotplug code.
  */
-static int xen_process_data(struct acpi_processor *_pr, int cpu)
+static int xen_process_data(struct acpi_processor *_pr)
 {
        int err = 0;
 
-       mutex_lock(&processors_done_mutex);
-       if (cpumask_test_cpu(cpu, to_cpumask(processors_done))) {
-               mutex_unlock(&processors_done_mutex);
+       mutex_lock(&acpi_ids_mutex);
+       if (__test_and_set_bit(_pr->acpi_id, acpi_ids_done)) {
+               mutex_unlock(&acpi_ids_mutex);
                return -EBUSY;
        }
        if (_pr->flags.power)
@@ -264,14 +263,76 @@ static int xen_process_data(struct acpi_processor *_pr, 
int cpu)
        if (_pr->performance && _pr->performance->states)
                err |= xen_push_pxx_to_hypervisor(_pr);
 
-       cpumask_set_cpu(cpu, to_cpumask(processors_done));
-       mutex_unlock(&processors_done_mutex);
+       mutex_unlock(&acpi_ids_mutex);
        return err;
 }
 
+/*
+ * Do not convert this to cpumask_var_t as that structure is limited to
+ * nr_cpu_ids and we can go beyound that.
+ */
+static unsigned long *acpi_id_present;
+
+static acpi_status
+xen_acpi_id_present(acpi_handle handle, u32 lvl, void *context, void **rv)
+{
+       u32 acpi_id;
+       acpi_status status;
+       acpi_object_type acpi_type;
+       unsigned long long tmp;
+       union acpi_object object = { 0 };
+       struct acpi_buffer buffer = { sizeof(union acpi_object), &object };
+
+       status = acpi_get_type(handle, &acpi_type);
+       if (ACPI_FAILURE(status))
+               return AE_OK;
+
+       switch (acpi_type) {
+       case ACPI_TYPE_PROCESSOR:
+               status = acpi_evaluate_object(handle, NULL, NULL, &buffer);
+               if (ACPI_FAILURE(status))
+                       return AE_OK;
+               acpi_id = object.processor.proc_id;
+               break;
+       case ACPI_TYPE_DEVICE:
+               status = acpi_evaluate_integer(handle, "_UID", NULL, &tmp);
+               if (ACPI_FAILURE(status))
+                       return AE_OK;
+               acpi_id = tmp;
+               break;
+       default:
+               return AE_OK;
+       }
+       if (acpi_id > NR_ACPI_CPUS) {
+               WARN_ONCE(1, "There are %d ACPI processors, but kernel can only 
do %d!\n",
+                    acpi_id, NR_ACPI_CPUS);
+               return AE_OK;
+       }
+       __set_bit(acpi_id, acpi_id_present);
+
+       return AE_OK;
+}
+static unsigned int xen_enumerate_acpi_id(void)
+{
+       unsigned int n = 0;
+
+       acpi_walk_namespace(ACPI_TYPE_PROCESSOR, ACPI_ROOT_OBJECT,
+                           ACPI_UINT32_MAX,
+                           xen_acpi_id_present, NULL, NULL, NULL);
+       acpi_get_devices("ACPI0007", xen_acpi_id_present, NULL, NULL);
+
+       mutex_lock(&acpi_ids_mutex);
+       if (!bitmap_equal(acpi_id_present, acpi_ids_done, MAX_ACPI_BITS))
+               n = bitmap_weight(acpi_id_present, MAX_ACPI_BITS);
+       mutex_unlock(&acpi_ids_mutex);
+
+       return n;
+}
+
 static int xen_processor_check(void)
 {
        struct cpufreq_policy *policy;
+       struct acpi_processor *pr_backup;
        int cpu;
 
        policy = cpufreq_cpu_get(smp_processor_id());
@@ -282,15 +343,40 @@ static int xen_processor_check(void)
        for_each_online_cpu(cpu) {
                struct acpi_processor *_pr;
 
-               _pr = per_cpu(processors, cpu);
+               _pr = per_cpu(processors, cpu /* APIC ID */);
                if (!_pr)
                        continue;
 
-               (void)xen_process_data(_pr, cpu);
+               if (!pr_backup) {
+                       pr_backup = kzalloc(sizeof(struct acpi_processor), 
GFP_KERNEL);
+                       memcpy(pr_backup, _pr, sizeof(struct acpi_processor));
+               }
+               (void)xen_process_data(_pr);
        }
        put_online_cpus();
 
        cpufreq_cpu_put(policy);
+
+       /* All online CPUs have been processed at this stage. Now verify
+        * whether in fact "online CPUs" == physical CPUs.
+        */
+       acpi_id_present = kcalloc(MAX_ACPI_BITS, sizeof(unsigned long), 
GFP_KERNEL);
+       if (!acpi_id_present)
+               goto err_out;
+       memset(acpi_id_present, 0, MAX_ACPI_BITS * sizeof(unsigned long));
+
+       if (xen_enumerate_acpi_id() && pr_backup) {
+               for_each_set_bit(cpu, acpi_id_present, MAX_ACPI_BITS) {
+                       pr_backup->acpi_id = cpu;
+                       /* We will get -EBUSY if it has been programmed 
already. */
+                       (void)xen_process_data(pr_backup);
+               }
+       }
+       kfree(acpi_id_present);
+       acpi_id_present = NULL;
+err_out:
+       kfree(pr_backup);
+       pr_backup = NULL;
        return 0;
 }
 /*
@@ -329,7 +415,7 @@ static int xen_cpu_soft_notify(struct notifier_block *nfb,
        struct acpi_processor *_pr = per_cpu(processors, cpu);
 
        if (action == CPU_ONLINE && _pr)
-               (void)xen_process_data(_pr, cpu);
+               (void)xen_process_data(_pr);
 
        return NOTIFY_OK;
 }
@@ -379,6 +465,10 @@ static int __init xen_processor_passthru_init(void)
        if (rc)
                return rc;
 
+       acpi_ids_done = kcalloc(MAX_ACPI_BITS, sizeof(unsigned long), 
GFP_KERNEL);
+       if (!acpi_ids_done)
+               return -ENOMEM;
+       memset(acpi_ids_done, 0, MAX_ACPI_BITS * sizeof(unsigned long));
        xen_processor_thread = kthread_run(xen_processor_thread_func, NULL, 
DRV_NAME);
        if (IS_ERR(xen_processor_thread)) {
                pr_err(DRV_NAME ": Failed to create thread. Aborting.\n");
@@ -392,6 +482,7 @@ static void __exit xen_processor_passthru_exit(void)
        unregister_hotcpu_notifier(&xen_cpu_notifier);
        if (xen_processor_thread)
                kthread_stop(xen_processor_thread);
+       kfree(acpi_ids_done);
 }
 late_initcall(xen_processor_passthru_init);
 module_exit(xen_processor_passthru_exit);
-- 
1.7.7.5


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