On Wed, 12 Jun 2019, Vitaly Kuznetsov wrote:

Dmitry Safonov [off-list ref] writes:

quoted

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 1608050e9df9..0bdd79ecbff8 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c

@@ -91,7 +91,7 @@ EXPORT_SYMBOL_GPL(hv_max_vp_index);
 static int hv_cpu_init(unsigned int cpu)
 {
 	u64 msr_vp_index;
-	struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
+	struct hv_vp_assist_page **hvp = &hv_vp_assist_page[cpu];
 	void **input_arg;
 	struct page *pg;
 

@@ -103,7 +103,7 @@ static int hv_cpu_init(unsigned int cpu)
 
 	hv_get_vp_index(msr_vp_index);
 
-	hv_vp_index[smp_processor_id()] = msr_vp_index;
+	hv_vp_index[cpu] = msr_vp_index;
 
 	if (msr_vp_index > hv_max_vp_index)
 		hv_max_vp_index = msr_vp_index;

The above is unrelated cleanup (as cpu == smp_processor_id() for
CPUHP_AP_ONLINE_DYN callbacks), right? As I'm pretty sure these can'd be
preempted.

They can be preempted, but they are guaranteed to run on the upcoming CPU,
i.e. smp_processor_id() is allowed even in preemptible context as the task
cannot migrate.

Thanks,

	tglx