KVM: PPC: Don't reload FPU with invalid values

When the guest activates the FPU, we load it up. That's fine when
it wasn't activated before on the host, but if it was we end up
reloading FPU values from last time the FPU was deactivated on the
host without writing the proper values back to the vcpu struct.

This patch checks if the FPU is enabled already and if so just doesn't
bother activating it, making FPU operations survive guest context switches.

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

diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index 358d5f78311a40fb5ad82a9adc8e62509f3a7e4e..6f409c98205ce19d5d1c767f8ca46cdabab0ae13 100644 (file)
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -702,6 +702,11 @@ static int kvmppc_handle_ext(struct kvm_vcpu *vcpu, unsigned int exit_nr,
                return RESUME_GUEST;
        }
 
+       /* We already own the ext */
+       if (vcpu->arch.guest_owned_ext & msr) {
+               return RESUME_GUEST;
+       }
+
 #ifdef DEBUG_EXT
        printk(KERN_INFO "Loading up ext 0x%lx\n", msr);
 #endif