KVM: Use the scheduler preemption notifiers to make kvm preemptible

Current kvm disables preemption while the new virtualization registers are
in use.  This of course is not very good for latency sensitive workloads (one
use of virtualization is to offload user interface and other latency
insensitive stuff to a container, so that it is easier to analyze the
remaining workload).  This patch re-enables preemption for kvm; preemption
is now only disabled when switching the registers in and out, and during
the switch to guest mode and back.

Contains fixes from Shaohua Li <shaohua.li@intel.com>.

Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index e92c84b04c1f..0667183ecbed 100644
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -13,6 +13,7 @@
 #include <linux/signal.h>
 #include <linux/sched.h>
 #include <linux/mm.h>
+#include <linux/preempt.h>
 #include <asm/signal.h>
 
 #include <linux/kvm.h>
@@ -301,6 +302,7 @@ void kvm_io_bus_register_dev(struct kvm_io_bus *bus,
 
 struct kvm_vcpu {
         struct kvm *kvm;
+        struct preempt_notifier preempt_notifier;
         int vcpu_id;
         struct mutex mutex;
         int   cpu;
@@ -429,7 +431,7 @@ struct kvm_arch_ops {
         struct kvm_vcpu *(*vcpu_create)(struct kvm *kvm, unsigned id);
         void (*vcpu_free)(struct kvm_vcpu *vcpu);
 
-        void (*vcpu_load)(struct kvm_vcpu *vcpu);
+        void (*vcpu_load)(struct kvm_vcpu *vcpu, int cpu);
         void (*vcpu_put)(struct kvm_vcpu *vcpu);
         void (*vcpu_decache)(struct kvm_vcpu *vcpu);