On 02/27/2014 05:40 AM, Raghavendra K T wrote:
On 02/26/2014 08:44 PM, 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 <[email protected]>
---
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;
+
kvm_kick_cpu_type() in patch 8 assumes that host has support for kick
hypercall (KVM_HC_KICK_CPU).
I think for that we need explicit check of this
kvm_para_has_feature(KVM_FEATURE_PV_UNHALT).
otherwise things may break for unlikely case of running a new guest on
a old host?
Unfair lock is a separate config option that does not need to do any cpu
kick. The checking of kvm_para_available() is just to make sure that the
kernel is running in a real PV environment, not on bare metal but with
CONFIG_PARAVIRT enabled.
-Longman
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