diff mbox series

[4.4,081/266] powerpc/fsl: Emulate SPRN_BUCSR register

Message ID 20190515090725.183169160@linuxfoundation.org (mailing list archive)
State Not Applicable
Headers show
Series None | expand

Commit Message

Greg KH May 15, 2019, 10:53 a.m. UTC 
From: Diana Craciun <diana.craciun@nxp.com>

commit 98518c4d8728656db349f875fcbbc7c126d4c973 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/powerpc/kvm/e500_emulate.c |    7 +++++++
 1 file changed, 7 insertions(+)
diff mbox series

Patch

--- a/arch/powerpc/kvm/e500_emulate.c
+++ b/arch/powerpc/kvm/e500_emulate.c
@@ -277,6 +277,13 @@  int kvmppc_core_emulate_mtspr_e500(struc
 		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: