#include <linux/types.h> /* FIXME: kvm_para.h needs this */
+#include <linux/stop_machine.h>
#include <linux/kvm_para.h>
#include <linux/uaccess.h>
#include <linux/module.h>
mtrr_type smp_type;
};
+static DEFINE_PER_CPU(struct cpu_stop_work, mtrr_work);
+
/**
- * ipi_handler - Synchronisation handler. Executed by "other" CPUs.
+ * mtrr_work_handler - Synchronisation handler. Executed by "other" CPUs.
* @info: pointer to mtrr configuration data
*
* Returns nothing.
*/
-static void ipi_handler(void *info)
+static int mtrr_work_handler(void *info)
{
#ifdef CONFIG_SMP
struct set_mtrr_data *data = info;
unsigned long flags;
+ atomic_dec(&data->count);
+ while (!atomic_read(&data->gate))
+ cpu_relax();
+
local_irq_save(flags);
atomic_dec(&data->count);
- while (!atomic_read(&data->gate))
+ while (atomic_read(&data->gate))
cpu_relax();
/* The master has cleared me to execute */
}
atomic_dec(&data->count);
- while (atomic_read(&data->gate))
+ while (!atomic_read(&data->gate))
cpu_relax();
atomic_dec(&data->count);
local_irq_restore(flags);
#endif
+ return 0;
}
static inline int types_compatible(mtrr_type type1, mtrr_type type2)
*
* This is kinda tricky, but fortunately, Intel spelled it out for us cleanly:
*
- * 1. Send IPI to do the following:
+ * 1. Queue work to do the following on all processors:
* 2. Disable Interrupts
* 3. Wait for all procs to do so
* 4. Enter no-fill cache mode
* 15. Enable interrupts.
*
* What does that mean for us? Well, first we set data.count to the number
- * of CPUs. As each CPU disables interrupts, it'll decrement it once. We wait
- * until it hits 0 and proceed. We set the data.gate flag and reset data.count.
- * Meanwhile, they are waiting for that flag to be set. Once it's set, each
+ * of CPUs. As each CPU announces that it started the rendezvous handler by
+ * decrementing the count, We reset data.count and set the data.gate flag
+ * allowing all the cpu's to proceed with the work. As each cpu disables
+ * interrupts, it'll decrement data.count once. We wait until it hits 0 and
+ * proceed. We clear the data.gate flag and reset data.count. Meanwhile, they
+ * are waiting for that flag to be cleared. Once it's cleared, each
* CPU goes through the transition of updating MTRRs.
* The CPU vendors may each do it differently,
* so we call mtrr_if->set() callback and let them take care of it.
* When they're done, they again decrement data->count and wait for data.gate
- * to be reset.
+ * to be set.
* When we finish, we wait for data.count to hit 0 and toggle the data.gate flag
* Everyone then enables interrupts and we all continue on.
*
{
struct set_mtrr_data data;
unsigned long flags;
+ int cpu;
+
+#ifdef CONFIG_SMP
+ /*
+ * If this cpu is not yet active, we are in the cpu online path. There
+ * can be no stop_machine() in parallel, as stop machine ensures this
+ * by using get_online_cpus(). We can skip taking the stop_cpus_mutex,
+ * as we don't need it and also we can't afford to block while waiting
+ * for the mutex.
+ *
+ * If this cpu is active, we need to prevent stop_machine() happening
+ * in parallel by taking the stop cpus mutex.
+ *
+ * Also, this is called in the context of cpu online path or in the
+ * context where cpu hotplug is prevented. So checking the active status
+ * of the raw_smp_processor_id() is safe.
+ */
+ if (cpu_active(raw_smp_processor_id()))
+ mutex_lock(&stop_cpus_mutex);
+#endif
+
+ preempt_disable();
data.smp_reg = reg;
data.smp_base = base;
atomic_set(&data.gate, 0);
/* Start the ball rolling on other CPUs */
- if (smp_call_function(ipi_handler, &data, 0) != 0)
- panic("mtrr: timed out waiting for other CPUs\n");
+ for_each_online_cpu(cpu) {
+ struct cpu_stop_work *work = &per_cpu(mtrr_work, cpu);
+
+ if (cpu == smp_processor_id())
+ continue;
+
+ stop_one_cpu_nowait(cpu, mtrr_work_handler, &data, work);
+ }
- local_irq_save(flags);
while (atomic_read(&data.count))
cpu_relax();
smp_wmb();
atomic_set(&data.gate, 1);
+ local_irq_save(flags);
+
+ while (atomic_read(&data.count))
+ cpu_relax();
+
+ /* Ok, reset count and toggle gate */
+ atomic_set(&data.count, num_booting_cpus() - 1);
+ smp_wmb();
+ atomic_set(&data.gate, 0);
+
/* Do our MTRR business */
/*
* HACK!
- * We use this same function to initialize the mtrrs on boot.
- * The state of the boot cpu's mtrrs has been saved, and we want
- * to replicate across all the APs.
- * If we're doing that @reg is set to something special...
+ *
+ * We use this same function to initialize the mtrrs during boot,
+ * resume, runtime cpu online and on an explicit request to set a
+ * specific MTRR.
+ *
+ * During boot or suspend, the state of the boot cpu's mtrrs has been
+ * saved, and we want to replicate that across all the cpus that come
+ * online (either at the end of boot or resume or during a runtime cpu
+ * online). If we're doing that, @reg is set to something special and on
+ * this cpu we still do mtrr_if->set_all(). During boot/resume, this
+ * is unnecessary if at this point we are still on the cpu that started
+ * the boot/resume sequence. But there is no guarantee that we are still
+ * on the same cpu. So we do mtrr_if->set_all() on this cpu aswell to be
+ * sure that we are in sync with everyone else.
*/
if (reg != ~0U)
mtrr_if->set(reg, base, size, type);
- else if (!mtrr_aps_delayed_init)
+ else
mtrr_if->set_all();
/* Wait for the others */
atomic_set(&data.count, num_booting_cpus() - 1);
smp_wmb();
- atomic_set(&data.gate, 0);
+ atomic_set(&data.gate, 1);
/*
* Wait here for everyone to have seen the gate change
cpu_relax();
local_irq_restore(flags);
+ preempt_enable();
+#ifdef CONFIG_SMP
+ if (cpu_active(raw_smp_processor_id()))
+ mutex_unlock(&stop_cpus_mutex);
+#endif
}
/**
}
/*
- * MTRR initialization for all AP's
+ * Delayed MTRR initialization for all AP's
*/
void mtrr_aps_init(void)
{
if (!use_intel())
return;
+ /*
+ * Check if someone has requested the delay of AP MTRR initialization,
+ * by doing set_mtrr_aps_delayed_init(), prior to this point. If not,
+ * then we are done.
+ */
+ if (!mtrr_aps_delayed_init)
+ return;
+
set_mtrr(~0U, 0, 0, 0);
mtrr_aps_delayed_init = false;
}
projects / linux-imx.git / blobdiff