Re: [PATCH delta V13 14/14] kvm : Paravirtual ticketlocks support for linux guests running on KVM hypervisor

[Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>]

* Ingo Molnar <mingo@kernel.org> [2013-08-13 18:55:52]:

> Would be nice to have a delta fix patch against tip:x86/spinlocks, which 
> I'll then backmerge into that series via rebasing it.
> 

There was a namespace collision of PER_CPU lock_waiting variable when
we have both Xen and KVM enabled. 

Perhaps this week wasn't for me. Had run 100 times randconfig in a loop
for the fix sent earlier :(. 

Ingo, below delta patch should fix it, IIRC, I hope you will be folding this
back to patch 14/14 itself. Else please let me.
I have already run allnoconfig, allyesconfig, randconfig with below patch. But will
test again. This should apply on top of tip:x86/spinlocks.

---8<---
From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>

Fix Namespace collision for lock_waiting

Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
---
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index d442471..b8ef630 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -673,7 +673,7 @@ struct kvm_lock_waiting {
 static cpumask_t waiting_cpus;
 
 /* Track spinlock on which a cpu is waiting */
-static DEFINE_PER_CPU(struct kvm_lock_waiting, lock_waiting);
+static DEFINE_PER_CPU(struct kvm_lock_waiting, klock_waiting);
 
 static void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
 {
@@ -685,7 +685,7 @@ static void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
 	if (in_nmi())
 		return;
 
-	w = &__get_cpu_var(lock_waiting);
+	w = &__get_cpu_var(klock_waiting);
 	cpu = smp_processor_id();
 	start = spin_time_start();
 
@@ -756,7 +756,7 @@ static void kvm_unlock_kick(struct arch_spinlock *lock, __ticket_t ticket)
 
 	add_stats(RELEASED_SLOW, 1);
 	for_each_cpu(cpu, &waiting_cpus) {
-		const struct kvm_lock_waiting *w = &per_cpu(lock_waiting, cpu);
+		const struct kvm_lock_waiting *w = &per_cpu(klock_waiting, cpu);
 		if (ACCESS_ONCE(w->lock) == lock &&
 		    ACCESS_ONCE(w->want) == ticket) {
 			add_stats(RELEASED_SLOW_KICKED, 1);