[Xen-devel] [RFC PATCH V5 08/14] xen: dynamically allocate cpu_evtchn_mask

[Wei Liu <wei.liu2@xxxxxxxxxx>]

The size of cpu_evtchn_mask can change, use dynamic allocation to cope with
this. To save space, cpu_evtchn_mask is not allocated for offline cpus. It
will get allocated as soon as a cpu goes online.

Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 drivers/xen/events.c |   57 ++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 53 insertions(+), 4 deletions(-)

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 217efb2..ee35ff9 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -30,6 +30,7 @@
 #include <linux/slab.h>
 #include <linux/irqnr.h>
 #include <linux/pci.h>
+#include <linux/cpu.h>
 
 #ifdef CONFIG_X86
 #include <asm/desc.h>
@@ -156,8 +157,7 @@ static bool (*pirq_needs_eoi)(unsigned irq);
 /* Find the first set bit in a evtchn mask */
 #define EVTCHN_FIRST_BIT(w) find_first_bit(BM(&(w)), BITS_PER_EVTCHN_WORD)
 
-static DEFINE_PER_CPU(xen_ulong_t [NR_EVENT_CHANNELS_L2/BITS_PER_EVTCHN_WORD],
-                     cpu_evtchn_mask);
+static DEFINE_PER_CPU(xen_ulong_t *, cpu_evtchn_mask);
 
 /* Xen will never allocate port zero for any purpose. */
 #define VALID_EVTCHN(chn)      ((chn) != 0)
@@ -356,6 +356,9 @@ static void bind_evtchn_to_cpu(unsigned int chn, unsigned 
int cpu)
 static void init_evtchn_cpu_bindings(void)
 {
        int i;
+       unsigned int nr = xen_nr_event_channels / BITS_PER_EVTCHN_WORD;
+       unsigned int nr_bytes = nr * sizeof(xen_ulong_t);
+
 #ifdef CONFIG_SMP
        struct irq_info *info;
 
@@ -366,9 +369,9 @@ static void init_evtchn_cpu_bindings(void)
        }
 #endif
 
-       for_each_possible_cpu(i)
+       for_each_online_cpu(i)
                memset(per_cpu(cpu_evtchn_mask, i),
-                      (i == 0) ? ~0 : 0, sizeof(*per_cpu(cpu_evtchn_mask, i)));
+                      (i == 0) ? ~0 : 0, nr_bytes);
 }
 
 static inline void clear_evtchn(int port)
@@ -1867,6 +1870,41 @@ const struct evtchn_ops evtchn_l2_ops = {
        .do_upcall = __xen_evtchn_do_upcall_l2
 };
 
+static int __cpuinit xen_events_notifier_cb(struct notifier_block *self,
+                                           unsigned long action,
+                                           void *hcpu)
+{
+       int cpu = (long)hcpu;
+       int rc = NOTIFY_OK;
+       void *p;
+       unsigned int nr = xen_nr_event_channels / BITS_PER_EVTCHN_WORD;
+       unsigned int nr_bytes = nr * sizeof(xen_ulong_t);
+
+       switch (action) {
+       case CPU_UP_PREPARE:
+               if (!per_cpu(cpu_evtchn_mask, cpu)) {
+                       p = kzalloc_node(sizeof(xen_ulong_t) * nr,
+                                        GFP_KERNEL, cpu_to_node(cpu));
+                       if (!p)
+                               rc = NOTIFY_BAD;
+                       else {
+                               per_cpu(cpu_evtchn_mask, cpu) = p;
+                               memset(per_cpu(cpu_evtchn_mask, cpu),
+                                      (cpu == 0) ? ~0 : 0, nr_bytes);
+                               rc = NOTIFY_OK;
+                       }
+               }
+               break;
+       default:
+               break;
+       }
+       return rc;
+}
+
+static struct notifier_block xen_events_notifier __cpuinitdata = {
+       .notifier_call = xen_events_notifier_cb,
+};
+
 void __init xen_init_IRQ(void)
 {
        int i;
@@ -1890,6 +1928,17 @@ void __init xen_init_IRQ(void)
        for (i = 0; i < xen_nr_event_channels; i++)
                evtchn_to_irq[i] = -1;
 
+       for_each_online_cpu(cpu) {
+               void *p;
+               unsigned int nr = xen_nr_event_channels / BITS_PER_EVTCHN_WORD;
+
+               p = kzalloc_node(sizeof(xen_ulong_t) * nr,
+                                GFP_KERNEL, cpu_to_node(cpu));
+               BUG_ON(!p);
+               per_cpu(cpu_evtchn_mask, cpu) = p;
+       }
+       register_cpu_notifier(&xen_events_notifier);
+
        init_evtchn_cpu_bindings();
 
        /* No event channels are 'live' right now. */
-- 
1.7.10.4


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