KVM: PPC: Convert MSR to shared page

One of the most obvious registers to share with the guest directly is the
MSR. The MSR contains the "interrupts enabled" flag which the guest has to
toggle in critical sections.

So in order to bring the overhead of interrupt en- and disabling down, let's
put msr into the shared page. Keep in mind that even though you can fully read
its contents, writing to it doesn't always update all state. There are a few
safe fields that don't require hypervisor interaction. See the documentation
for a list of MSR bits that are safe to be set from inside the guest.

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

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/powerpc/kvm/book3s_64_mmu_host.c b/arch/powerpc/kvm/book3s_64_mmu_host.c
index 384179a5002b..71c1f9027abb 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_host.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_host.c
@@ -66,7 +66,7 @@ static struct kvmppc_sid_map *find_sid_vsid(struct kvm_vcpu *vcpu, u64 gvsid)
         struct kvmppc_sid_map *map;
         u16 sid_map_mask;
 
-        if (vcpu->arch.msr & MSR_PR)
+        if (vcpu->arch.shared->msr & MSR_PR)
                 gvsid |= VSID_PR;
 
         sid_map_mask = kvmppc_sid_hash(vcpu, gvsid);
@@ -191,7 +191,7 @@ static struct kvmppc_sid_map *create_sid_map(struct kvm_vcpu *vcpu, u64 gvsid)
         u16 sid_map_mask;
         static int backwards_map = 0;
 
-        if (vcpu->arch.msr & MSR_PR)
+        if (vcpu->arch.shared->msr & MSR_PR)
                 gvsid |= VSID_PR;
 
         /* We might get collisions that trap in preceding order, so let's