x86 mtrr: Fix set_mtrr() race against cpu_online_map changes.

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>

diff --git a/xen/arch/x86/cpu/mtrr/main.c b/xen/arch/x86/cpu/mtrr/main.c
index 1acd03a5a6eb5bcbc07dfab2093d3f84ae55ae14..f99054468cc355c1d2579cb5ba7dc781c8949529 100644 (file)
--- a/xen/arch/x86/cpu/mtrr/main.c
+++ b/xen/arch/x86/cpu/mtrr/main.c
@@ -229,29 +229,32 @@ static inline int types_compatible(mtrr_type type1, mtrr_type type2) {
 static void set_mtrr(unsigned int reg, unsigned long base,
                     unsigned long size, mtrr_type type)
 {
+       cpumask_t allbutself;
+       unsigned int nr_cpus;
        struct set_mtrr_data data;
        unsigned long flags;
 
+       allbutself = cpu_online_map;
+       cpu_clear(smp_processor_id(), allbutself);
+       nr_cpus = cpus_weight(allbutself);
+
        data.smp_reg = reg;
        data.smp_base = base;
        data.smp_size = size;
        data.smp_type = type;
-       atomic_set(&data.count, num_online_cpus() - 1);
-       /* make sure data.count is visible before unleashing other CPUs */
-       smp_wmb();
+       atomic_set(&data.count, nr_cpus);
        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");
+       /* Start the ball rolling on other CPUs */
+       on_selected_cpus(&allbutself, ipi_handler, &data, 0);
 
        local_irq_save(flags);
 
-       while(atomic_read(&data.count))
+       while (atomic_read(&data.count))
                cpu_relax();
 
        /* ok, reset count and toggle gate */
-       atomic_set(&data.count, num_online_cpus() - 1);
+       atomic_set(&data.count, nr_cpus);
        smp_wmb();
        atomic_set(&data.gate,1);
 
@@ -271,10 +274,10 @@ static void set_mtrr(unsigned int reg, unsigned long base,
                mtrr_if->set(reg,base,size,type);
 
        /* wait for the others */
-       while(atomic_read(&data.count))
+       while (atomic_read(&data.count))
                cpu_relax();
 
-       atomic_set(&data.count, num_online_cpus() - 1);
+       atomic_set(&data.count, nr_cpus);
        smp_wmb();
        atomic_set(&data.gate,0);
 
@@ -282,7 +285,7 @@ static void set_mtrr(unsigned int reg, unsigned long base,
         * Wait here for everyone to have seen the gate change
         * So we're the last ones to touch 'data'
         */
-       while(atomic_read(&data.count))
+       while (atomic_read(&data.count))
                cpu_relax();
 
        local_irq_restore(flags);