Subject: [PATCH v5 4/5] KVM: PPC: mmio: Return to guest after emulation failure

From: Fabiano Rosas <[email-masked]>
Date: Tue, 25 Jan 2022 18:56:54 -0300

If MMIO emulation fails we don't want to crash the whole guest by
returning to userspace.

The original commit bbf45ba57eae ("KVM: ppc: PowerPC 440 KVM
implementation") added a todo:

  /* XXX Deliver Program interrupt to guest. */

and later the commit d69614a295ae ("KVM: PPC: Separate loadstore
emulation from priv emulation") added the Program interrupt injection
but in another file, so I'm assuming it was missed that this block
needed to be altered.

Also change the message to a ratelimited one since we're letting the
guest run and it could flood the host logs.

Signed-off-by: Fabiano Rosas <[email-masked]>
Reviewed-by: Nicholas Piggin <[email-masked]>
---
 arch/powerpc/kvm/powerpc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 27fb2b70f631..acb0d2a4bdb9 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -307,9 +307,9 @@ int kvmppc_emulate_mmio(struct kvm_vcpu *vcpu)
 		u32 last_inst;
 
 		kvmppc_get_last_inst(vcpu, INST_GENERIC, &last_inst);
-		/* XXX Deliver Program interrupt to guest. */
-		pr_emerg("%s: emulation failed (%08x)\n", __func__, last_inst);
-		r = RESUME_HOST;
+		kvm_debug_ratelimited("Guest access to device memory using unsupported instruction (opcode: %#08x)\n",
+				      last_inst);
+		r = RESUME_GUEST;
 		break;
 	}
 	default:
-- 
2.34.1