[Xen-devel] [PATCH] x86: correct socket_cpumask allocation for AP

[Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>]

For AP, phys_proc_id is still not valid in CPU_PREPARE notifier
(cpu_smpboot_alloc), so cpu_to_socket(cpu) is not valid as well.

Introduce a pre-allocated secondary_cpu_mask so that later in
smp_store_cpu_info() socket_cpumask[socket] can consume it.

Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
---
This is targeted for staging branch.
I tested on a 2-sockets machine and looks fine.
---
 xen/arch/x86/smpboot.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index c73aa1b..49b8497 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -62,6 +62,7 @@ EXPORT_SYMBOL(cpu_online_map);
 
 unsigned int __read_mostly nr_sockets;
 cpumask_var_t *__read_mostly socket_cpumask;
+static cpumask_var_t secondary_socket_cpumask;
 
 struct cpuinfo_x86 cpu_data[NR_CPUS];
 
@@ -84,11 +85,21 @@ void *stack_base[NR_CPUS];
 static void smp_store_cpu_info(int id)
 {
     struct cpuinfo_x86 *c = cpu_data + id;
+    unsigned int socket;
 
     *c = boot_cpu_data;
     if ( id != 0 )
+    {
         identify_cpu(c);
 
+        socket = cpu_to_socket(id);
+        if ( !socket_cpumask[socket] )
+        {
+            socket_cpumask[socket] = secondary_socket_cpumask;
+            secondary_socket_cpumask = NULL;
+        }
+    }
+
     /*
      * Certain Athlons might work (for various values of 'work') in SMP
      * but they are not certified as MP capable.
@@ -705,7 +716,6 @@ static int cpu_smpboot_alloc(unsigned int cpu)
     nodeid_t node = cpu_to_node(cpu);
     struct desc_struct *gdt;
     unsigned long stub_page;
-    unsigned int socket = cpu_to_socket(cpu);
 
     if ( node != NUMA_NO_NODE )
         memflags = MEMF_node(node);
@@ -748,8 +758,8 @@ static int cpu_smpboot_alloc(unsigned int cpu)
         goto oom;
     per_cpu(stubs.addr, cpu) = stub_page + STUB_BUF_CPU_OFFS(cpu);
 
-    if ( !socket_cpumask[socket] &&
-         !zalloc_cpumask_var(socket_cpumask + socket) )
+    if ( !secondary_socket_cpumask &&
+         !zalloc_cpumask_var(&secondary_socket_cpumask) )
         goto oom;
 
     if ( zalloc_cpumask_var(&per_cpu(cpu_sibling_mask, cpu)) &&
-- 
1.9.1


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