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>
diff --git a/arch/powerpc/kvm/book3s_32_mmu_host.c b/arch/powerpc/kvm/book3s_32_mmu_host.c
index 0b51ef8..67b8c38 100644
--- a/arch/powerpc/kvm/book3s_32_mmu_host.c
+++ b/arch/powerpc/kvm/book3s_32_mmu_host.c
@@ -86,7 +86,7 @@
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);
@@ -253,7 +253,7 @@
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