[Xen-devel] [PATCH v2] x86: Factor out common CPU initialization code

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

Some of x86 bare-metal and Xen CPU initialization code is common between the two
and therefore can be factored out to avoid code duplication.

As a side effect, doing so will also extend the fix provided by commit
a7fcf28d431e ("x86/asm/entry: Replace this_cpu_sp0() with current_top_of_stack()
to x86_32") to 32-bit Xen PV guests.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
v2: Rebased on top of tip:master


 arch/x86/include/asm/smp.h |    1 +
 arch/x86/kernel/smpboot.c  |   37 ++++++++++++++++++++++---------------
 arch/x86/xen/smp.c         |   13 +------------
 3 files changed, 24 insertions(+), 27 deletions(-)

diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index a5cb4f6..17a8dce 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -153,6 +153,7 @@ void cpu_disable_common(void);
 void native_smp_prepare_boot_cpu(void);
 void native_smp_prepare_cpus(unsigned int max_cpus);
 void native_smp_cpus_done(unsigned int max_cpus);
+void common_cpu_up(unsigned int cpunum, struct task_struct *tidle);
 int native_cpu_up(unsigned int cpunum, struct task_struct *tidle);
 int native_cpu_disable(void);
 int common_cpu_die(unsigned int cpu);
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 9d26a67..c8616b9 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -776,6 +776,26 @@ out:
        return boot_error;
 }
 
+void common_cpu_up(unsigned int cpu, struct task_struct *idle)
+{
+       /* Just in case we booted with a single CPU. */
+       alternatives_enable_smp();
+
+       per_cpu(current_task, cpu) = idle;
+
+#ifdef CONFIG_X86_32
+       /* Stack for startup_32 can be just as for start_secondary onwards */
+       irq_ctx_init(cpu);
+       per_cpu(cpu_current_top_of_stack, cpu) =
+               (unsigned long)task_stack_page(idle) + THREAD_SIZE;
+#else
+       clear_tsk_thread_flag(idle, TIF_FORK);
+       initial_gs = per_cpu_offset(cpu);
+#endif
+       per_cpu(kernel_stack, cpu) =
+               (unsigned long)task_stack_page(idle) + THREAD_SIZE;
+}
+
 /*
  * NOTE - on most systems this is a PHYSICAL apic ID, but on multiquad
  * (ie clustered apic addressing mode), this is a LOGICAL apic ID.
@@ -793,24 +813,9 @@ static int do_boot_cpu(int apicid, int cpu, struct 
task_struct *idle)
        int cpu0_nmi_registered = 0;
        unsigned long timeout;
 
-       /* Just in case we booted with a single CPU. */
-       alternatives_enable_smp();
-
        idle->thread.sp = (unsigned long) (((struct pt_regs *)
                          (THREAD_SIZE +  task_stack_page(idle))) - 1);
-       per_cpu(current_task, cpu) = idle;
 
-#ifdef CONFIG_X86_32
-       /* Stack for startup_32 can be just as for start_secondary onwards */
-       irq_ctx_init(cpu);
-       per_cpu(cpu_current_top_of_stack, cpu) =
-               (unsigned long)task_stack_page(idle) + THREAD_SIZE;
-#else
-       clear_tsk_thread_flag(idle, TIF_FORK);
-       initial_gs = per_cpu_offset(cpu);
-#endif
-       per_cpu(kernel_stack, cpu) =
-               (unsigned long)task_stack_page(idle) + THREAD_SIZE;
        early_gdt_descr.address = (unsigned long)get_cpu_gdt_table(cpu);
        initial_code = (unsigned long)start_secondary;
        stack_start  = idle->thread.sp;
@@ -954,6 +959,8 @@ int native_cpu_up(unsigned int cpu, struct task_struct 
*tidle)
        /* the FPU context is blank, nobody can own it */
        __cpu_disable_lazy_restore(cpu);
 
+       common_cpu_up(cpu, tidle);
+
        err = do_boot_cpu(apicid, cpu, tidle);
        if (err) {
                pr_err("do_boot_cpu failed(%d) to wakeup CPU#%u\n", err, cpu);
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 2136b59..8648438 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -441,14 +441,7 @@ static int xen_cpu_up(unsigned int cpu, struct task_struct 
*idle)
 {
        int rc;
 
-       per_cpu(current_task, cpu) = idle;
-#ifdef CONFIG_X86_32
-       irq_ctx_init(cpu);
-#else
-       clear_tsk_thread_flag(idle, TIF_FORK);
-#endif
-       per_cpu(kernel_stack, cpu) =
-               (unsigned long)task_stack_page(idle) + THREAD_SIZE;
+       common_cpu_up(cpu, idle);
 
        xen_setup_runstate_info(cpu);
        xen_setup_timer(cpu);
@@ -469,10 +462,6 @@ static int xen_cpu_up(unsigned int cpu, struct task_struct 
*idle)
        if (rc)
                return rc;
 
-       if (num_online_cpus() == 1)
-               /* Just in case we booted with a single CPU. */
-               alternatives_enable_smp();
-
        rc = xen_smp_intr_init(cpu);
        if (rc)
                return rc;
-- 
1.7.1


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