KVM: PPC: Book3S: PR: Enable alternative instruction for SC 1

When running on top of pHyp, the hypercall instruction "sc 1" goes
straight into pHyp without trapping in supervisor mode.

So if we want to support PAPR guest in this configuration we need to
add a second way of accessing PAPR hypercalls, preferably with the
exact same semantics except for the instruction.

So let's overlay an officially reserved instruction and emulate PAPR
hypercalls whenever we hit that one.
Signed-off-by: Alexander Graf <agraf@suse.de>

arch/powerpc/include/asm/kvm_ppc.h

@@ -44,6 +44,7 @@ enum emulation_result {
 	EMULATE_DO_DCR,       /* kvm_run filled with DCR request */
 	EMULATE_FAIL,         /* can't emulate this instruction */
 	EMULATE_AGAIN,        /* something went wrong. go again */
+	EMULATE_DO_PAPR,      /* kvm_run filled with PAPR request */
 };
 
 extern int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu);

arch/powerpc/kvm/book3s_emulate.c

@@ -34,6 +34,8 @@
 #define OP_31_XOP_MTSRIN	242
 #define OP_31_XOP_TLBIEL	274
 #define OP_31_XOP_TLBIE		306
+/* Opcode is officially reserved, reuse it as sc 1 when sc 1 doesn't trap */
+#define OP_31_XOP_FAKE_SC1	308
 #define OP_31_XOP_SLBMTE	402
 #define OP_31_XOP_SLBIE		434
 #define OP_31_XOP_SLBIA		498
@@ -170,6 +172,32 @@ int kvmppc_core_emulate_op(struct kvm_run *run, struct kvm_vcpu *vcpu,
 			vcpu->arch.mmu.tlbie(vcpu, addr, large);
 			break;
 		}
+#ifdef CONFIG_KVM_BOOK3S_64_PR
+		case OP_31_XOP_FAKE_SC1:
+		{
+			/* SC 1 papr hypercalls */
+			ulong cmd = kvmppc_get_gpr(vcpu, 3);
+			int i;
+
+		        if ((vcpu->arch.shared->msr & MSR_PR) ||
+			    !vcpu->arch.papr_enabled) {
+				emulated = EMULATE_FAIL;
+				break;
+			}
+
+			if (kvmppc_h_pr(vcpu, cmd) == EMULATE_DONE)
+				break;
+
+			run->papr_hcall.nr = cmd;
+			for (i = 0; i < 9; ++i) {
+				ulong gpr = kvmppc_get_gpr(vcpu, 4 + i);
+				run->papr_hcall.args[i] = gpr;
+			}
+
+			emulated = EMULATE_DO_PAPR;
+			break;
+		}
+#endif
 		case OP_31_XOP_EIOIO:
 			break;
 		case OP_31_XOP_SLBMTE:

arch/powerpc/kvm/book3s_pr.c

@@ -760,6 +760,11 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
 			run->exit_reason = KVM_EXIT_MMIO;
 			r = RESUME_HOST_NV;
 			break;
+		case EMULATE_DO_PAPR:
+			run->exit_reason = KVM_EXIT_PAPR_HCALL;
+			vcpu->arch.hcall_needed = 1;
+			r = RESUME_HOST_NV;
+			break;
 		default:
 			BUG();
 		}