KVM: PPC: Introduce shared page

For transparent variable sharing between the hypervisor and guest, I introduce
a shared page. This shared page will contain all the registers the guest can
read and write safely without exiting guest context.

This patch only implements the stubs required for the basic structure of the
shared page. The actual register moving follows.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/44x.c b/arch/powerpc/kvm/44x.c
index 73c0a3f64ed1..e7b1f3fca5dc 100644
--- a/arch/powerpc/kvm/44x.c
+++ b/arch/powerpc/kvm/44x.c
@@ -123,8 +123,14 @@ struct kvm_vcpu *kvmppc_core_vcpu_create(struct kvm *kvm, unsigned int id)
         if (err)
                 goto free_vcpu;
 
+        vcpu->arch.shared = (void*)__get_free_page(GFP_KERNEL|__GFP_ZERO);
+        if (!vcpu->arch.shared)
+                goto uninit_vcpu;
+
         return vcpu;
 
+uninit_vcpu:
+        kvm_vcpu_uninit(vcpu);
 free_vcpu:
         kmem_cache_free(kvm_vcpu_cache, vcpu_44x);
 out:
@@ -135,6 +141,7 @@ void kvmppc_core_vcpu_free(struct kvm_vcpu *vcpu)
 {
         struct kvmppc_vcpu_44x *vcpu_44x = to_44x(vcpu);
 
+        free_page((unsigned long)vcpu->arch.shared);
         kvm_vcpu_uninit(vcpu);
         kmem_cache_free(kvm_vcpu_cache, vcpu_44x);
 }