[Xen-changelog] [xen master] x86/SMP: CPU0's scratch mask is needed earlier

[patchbot@xxxxxxx]

commit 7469686ccc959765542cd10551f9bd7a602f2cbd
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Mon Dec 19 11:49:20 2016 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Dec 19 11:49:20 2016 +0100

    x86/SMP: CPU0's scratch mask is needed earlier
    
    When putting together commit 3b61726458 ("x86: introduce and use
    scratch CPU mask") I failed to remember that AMD IOMMU setups needs the
    scratch mask prior to smp_prepare_cpus() having run. Use a static mask
    for the boot CPU instead.
    
    Note that the definition of scratch_cpu0mask could also be put inside a
    "NR_CPUS > 2 * BITS_PER_LONG" conditional, but it seems preferable to
    me to carry the extra variable in all cases and avoid the #ifdef-ary.
    
    Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/smpboot.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index ba651fb..9b390b8 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -57,6 +57,7 @@ DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_sibling_mask);
 DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_core_mask);
 
 DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, scratch_cpumask);
+static cpumask_t scratch_cpu0mask;
 
 cpumask_t cpu_online_map __read_mostly;
 EXPORT_SYMBOL(cpu_online_map);
@@ -648,7 +649,8 @@ static void cpu_smpboot_free(unsigned int cpu)
 
     free_cpumask_var(per_cpu(cpu_sibling_mask, cpu));
     free_cpumask_var(per_cpu(cpu_core_mask, cpu));
-    free_cpumask_var(per_cpu(scratch_cpumask, cpu));
+    if ( per_cpu(scratch_cpumask, cpu) != &scratch_cpu0mask )
+        free_cpumask_var(per_cpu(scratch_cpumask, cpu));
 
     if ( per_cpu(stubs.addr, cpu) )
     {
@@ -795,8 +797,7 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
         panic("No memory for socket CPU siblings map");
 
     if ( !zalloc_cpumask_var(&per_cpu(cpu_sibling_mask, 0)) ||
-         !zalloc_cpumask_var(&per_cpu(cpu_core_mask, 0)) ||
-         !alloc_cpumask_var(&per_cpu(scratch_cpumask, 0)) )
+         !zalloc_cpumask_var(&per_cpu(cpu_core_mask, 0)) )
         panic("No memory for boot CPU sibling/core maps");
 
     set_cpu_sibling_map(0);
@@ -850,8 +851,13 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
 
 void __init smp_prepare_boot_cpu(void)
 {
-    cpumask_set_cpu(smp_processor_id(), &cpu_online_map);
-    cpumask_set_cpu(smp_processor_id(), &cpu_present_map);
+    unsigned int cpu = smp_processor_id();
+
+    cpumask_set_cpu(cpu, &cpu_online_map);
+    cpumask_set_cpu(cpu, &cpu_present_map);
+#if NR_CPUS > 2 * BITS_PER_LONG
+    per_cpu(scratch_cpumask, cpu) = &scratch_cpu0mask;
+#endif
 }
 
 static void
--
generated by git-patchbot for /home/xen/git/xen.git#master

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