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, 0 insertions, 2 deletions

diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index 5437de2aa2d8..396c736e546b 100644
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -276,9 +276,7 @@ static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
         kvm_mmu_free_some_pages(vcpu);
         if (r < 0) {
                 spin_unlock(&vcpu->kvm->lock);
-                kvm_arch_ops->vcpu_put(vcpu);
                 r = __mmu_topup_memory_caches(vcpu, GFP_KERNEL);
-                kvm_arch_ops->vcpu_load(vcpu);
                 spin_lock(&vcpu->kvm->lock);
                 kvm_mmu_free_some_pages(vcpu);
         }