powerpc/fsl: Emulate SPRN_BUCSR register

In order to flush the branch predictor the guest kernel performs
writes to the BUCSR register which is hypervisor privilleged. However,
the branch predictor is flushed at each KVM entry, so the branch
predictor has been already flushed, so just return as soon as possible
to guest.

Signed-off-by: Diana Craciun <diana.craciun@nxp.com>
[mpe: Tweak comment formatting]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/kvm/e500_emulate.c b/arch/powerpc/kvm/e500_emulate.c
index 3f8189e..fde1de0 100644 (file)
--- a/arch/powerpc/kvm/e500_emulate.c
+++ b/arch/powerpc/kvm/e500_emulate.c
@@ -277,6 +277,13 @@ int kvmppc_core_emulate_mtspr_e500(struct kvm_vcpu *vcpu, int sprn, ulong spr_va
                vcpu->arch.pwrmgtcr0 = spr_val;
                break;
 
+       case SPRN_BUCSR:
+               /*
+                * If we are here, it means that we have already flushed the
+                * branch predictor, so just return to guest.
+                */
+               break;
+
        /* extra exceptions */
 #ifdef CONFIG_SPE_POSSIBLE
        case SPRN_IVOR32: