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Re: [Xen-devel] [PATCH RFC v5 5/8] pvqspinlock, x86: Enable unfair queue spinlock in a KVM guest
- To: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
- From: Waiman Long <waiman.long@xxxxxx>
- Date: Fri, 28 Feb 2014 12:08:47 -0500
- Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, Andi Kleen <andi@xxxxxxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Michel Lespinasse <walken@xxxxxxxxxx>, Alok Kataria <akataria@xxxxxxxxxx>, linux-arch@xxxxxxxxxxxxxxx, x86@xxxxxxxxxx, Ingo Molnar <mingo@xxxxxxxxxx>, Scott J Norton <scott.norton@xxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>, Alexander Fyodorov <halcy@xxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, Daniel J Blueman <daniel@xxxxxxxxxxxxx>, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, Oleg Nesterov <oleg@xxxxxxxxxx>, Steven Rostedt <rostedt@xxxxxxxxxxx>, Chris Wright <chrisw@xxxxxxxxxxxx>, George Spelvin <linux@xxxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Aswin Chandramouleeswaran <aswin@xxxxxx>, Chegu Vinod <chegu_vinod@xxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, David Vrabel <david.vrabel@xxxxxxxxxx>, Paolo Bonzini <pbonzini@xxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
- Delivery-date: Fri, 28 Feb 2014 17:08:59 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
On 02/26/2014 12:08 PM, Konrad Rzeszutek Wilk wrote:
On Wed, Feb 26, 2014 at 10:14:25AM -0500, Waiman Long wrote:
This patch adds a KVM init function to activate the unfair queue
spinlock in a KVM guest when the PARAVIRT_UNFAIR_LOCKS kernel config
option is selected.
Signed-off-by: Waiman Long<Waiman.Long@xxxxxx>
---
arch/x86/kernel/kvm.c | 17 +++++++++++++++++
1 files changed, 17 insertions(+), 0 deletions(-)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 713f1b3..a489140 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -826,3 +826,20 @@ static __init int kvm_spinlock_init_jump(void)
early_initcall(kvm_spinlock_init_jump);
#endif /* CONFIG_PARAVIRT_SPINLOCKS */
+
+#ifdef CONFIG_PARAVIRT_UNFAIR_LOCKS
+/*
+ * Enable unfair lock if running in a real para-virtualized environment
+ */
+static __init int kvm_unfair_locks_init_jump(void)
+{
+ if (!kvm_para_available())
+ return 0;
I think you also need to check for !kvm_para_has_feature(KVM_FEATURE_PV_UNHALT)?
Otherwise you might enable this, but the kicker function won't be
enabled.
The unfair lock code doesn't need to use the CPU kicker function. That
is why the KVM_FEATURE_PV_UNHALT feature is not checked.
-Longman
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