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

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Message-ID: <20130813200211.GA27811@linux.vnet.ibm.com>
Date:	Wed, 14 Aug 2013 01:32:11 +0530
From:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org, jeremy@...p.org,
	konrad.wilk@...cle.com, gleb@...hat.com, pbonzini@...hat.com,
	gregkh@...e.de, peterz@...radead.org, tglx@...utronix.de,
	agraf@...e.de, riel@...hat.com, avi.kivity@...il.com,
	habanero@...ux.vnet.ibm.com, chegu_vinod@...com,
	ouyang@...pitt.edu, drjones@...hat.com, attilio.rao@...rix.com,
	linux-doc@...r.kernel.org, torvalds@...ux-foundation.org,
	kvm@...r.kernel.org, andi@...stfloor.org,
	xen-devel@...ts.xensource.com,
	virtualization@...ts.linux-foundation.org,
	stefano.stabellini@...citrix.com, mtosatti@...hat.com,
	srivatsa.vaddagiri@...il.com,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Suzuki Poulose <suzuki@...ibm.com>
Subject: Re: [PATCH delta V13 14/14] kvm : Paravirtual ticketlocks support
 for linux guests running on KVM hypervisor

* Ingo Molnar <mingo@...nel.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@...ux.vnet.ibm.com>

Fix Namespace collision for lock_waiting

Signed-off-by: Raghavendra K T <raghavendra.kt@...ux.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);


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