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

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Date:	Tue, 13 Aug 2013 13:00:22 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
CC:	Ingo Molnar <mingo@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	linux-kernel@...r.kernel.org, x86@...nel.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

On 08/13/2013 01:02 PM, Raghavendra K T wrote:
> * 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);

Has static stopped meaning static?

    J

>  
>  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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