powerpc/fsl: Flush branch predictor when entering KVM

commit e7aa61f47b23afbec41031bc47ca8d6cb6516abc upstream.

Switching from the guest to host is another place
where the speculative accesses can be exploited.
Flush the branch predictor when entering KVM.
Signed-off-by: NDiana Craciun <diana.craciun@nxp.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/powerpc/kvm/bookehv_interrupts.S

@@ -75,6 +75,10 @@
 	PPC_LL	r1, VCPU_HOST_STACK(r4)
 	PPC_LL	r2, HOST_R2(r1)
 
+START_BTB_FLUSH_SECTION
+	BTB_FLUSH(r10)
+END_BTB_FLUSH_SECTION
+
 	mfspr	r10, SPRN_PID
 	lwz	r8, VCPU_HOST_PID(r4)
 	PPC_LL	r11, VCPU_SHARED(r4)