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, 2 insertions, 4 deletions

diff --git a/drivers/kvm/svm.c b/drivers/kvm/svm.c
index 0feec8558599..3997bbd78fb7 100644
--- a/drivers/kvm/svm.c
+++ b/drivers/kvm/svm.c
@@ -625,12 +625,11 @@ static void svm_free_vcpu(struct kvm_vcpu *vcpu)
         kfree(svm);
 }
 
-static void svm_vcpu_load(struct kvm_vcpu *vcpu)
+static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
         struct vcpu_svm *svm = to_svm(vcpu);
-        int cpu, i;
+        int i;
 
-        cpu = get_cpu();
         if (unlikely(cpu != vcpu->cpu)) {
                 u64 tsc_this, delta;
 
@@ -657,7 +656,6 @@ static void svm_vcpu_put(struct kvm_vcpu *vcpu)
                 wrmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]);
 
         rdtscll(vcpu->host_tsc);
-        put_cpu();
 }
 
 static void svm_vcpu_decache(struct kvm_vcpu *vcpu)