Re: [PATCH][tip] x86/paravirt: Make the virt_spin_lock_key setup after jump_label_init()

[Vitaly Kuznetsov]

Boris Petkov <bp@xxxxxxx> writes:

> On October 27, 2017 6:02:00 PM GMT+02:00, Dou Liyang <douly.fnst@xxxxxxxxxxxxxx> wrote:
>>Commit:
>>
>>  9043442b43b1 ("locking/paravirt: Use new static key for controlling
>>  call of virt_spin_lock()")
>>
>>set the static virt_spin_lock_key to a value before jump_label_init()
>>has been called, which will result in a WARN().
>>
>>Move the native_pv_lock_init() into xx_smp_prepare_cpus(). Make the
>>setup later to avoid the WARN().
>>
>>Reported-by: Juergen Gross <jgross@xxxxxxxx>
>>Suggested-by: Juergen Gross <jgross@xxxxxxxx>
>>Signed-off-by: Dou Liyang <douly.fnst@xxxxxxxxxxxxxx>
>>---
>> arch/x86/kernel/smpboot.c | 3 ++-
>> arch/x86/xen/smp_pv.c     | 2 ++
>> arch/x86/xen/spinlock.c   | 6 ++++--
>> 3 files changed, 8 insertions(+), 3 deletions(-)
>>
>>diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
>>index aed1460..6b1335a 100644
>>--- a/arch/x86/kernel/smpboot.c
>>+++ b/arch/x86/kernel/smpboot.c
>>@@ -1323,6 +1323,8 @@ void __init native_smp_prepare_cpus(unsigned int
>>max_cpus)
>> 	pr_info("CPU0: ");
>> 	print_cpu_info(&cpu_data(0));
>> 
>>+	native_pv_lock_init();
>>+
>> 	uv_system_init();
>> 
>> 	set_mtrr_aps_delayed_init();
>>@@ -1350,7 +1352,6 @@ void __init native_smp_prepare_boot_cpu(void)
>> 	/* already set me in cpu_online_mask in boot_cpu_init() */
>> 	cpumask_set_cpu(me, cpu_callout_mask);
>> 	cpu_set_state_online(me);
>>-	native_pv_lock_init();
>> }
>> 
>> void __init native_smp_cpus_done(unsigned int max_cpus)
>>diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c
>>index 5147140..570b2bc 100644
>>--- a/arch/x86/xen/smp_pv.c
>>+++ b/arch/x86/xen/smp_pv.c
>>@@ -236,6 +236,8 @@ static void __init xen_pv_smp_prepare_cpus(unsigned
>>int max_cpus)
>> 		xen_raw_printk(m);
>> 		panic(m);
>> 	}
>>+	native_pv_lock_init();
>>+
>> 	xen_init_lock_cpu(0);
>> 
>> 	smp_store_boot_cpu_info();
>>diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
>>index e8ab80a..1e1462d 100644
>>--- a/arch/x86/xen/spinlock.c
>>+++ b/arch/x86/xen/spinlock.c
>>@@ -81,8 +81,11 @@ void xen_init_lock_cpu(int cpu)
>> 	int irq;
>> 	char *name;
>> 
>>-	if (!xen_pvspin)
>>+	if (!xen_pvspin) {
>>+		if (cpu == 0)
>>+			static_branch_disable(&virt_spin_lock_key);
>
> This is assuming CPU 0 is the boot cpu. I think you want boot_cpu_data.cpu_index here or whatever is used on xen to identify the BSP reliably. 

It seems both PV and PVHVM call xen_init_lock_cpu(0) so 0 here is
Linux's idea of CPU id, not Xen's.

In case Xen's idea is needed xen_vcpu_id mapping should be used. But I
don't think it's the case here.

-- 
  Vitaly