[PULL,22/24] powerpc/kvm: support to handle sw breakpoint

diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
index 73063ef..dbd160f 100644
--- a/arch/powerpc/include/asm/kvm_ppc.h
+++ b/arch/powerpc/include/asm/kvm_ppc.h
@@ -38,6 +38,12 @@ 
 #include <asm/paca.h>
 #endif
 
+/*
+ * KVMPPC_INST_SW_BREAKPOINT is debug Instruction
+ * for supporting software breakpoint.
+ */
+#define KVMPPC_INST_SW_BREAKPOINT	0x00dddd00
+
 enum emulation_result {
 	EMULATE_DONE,         /* no further processing */
 	EMULATE_DO_MMIO,      /* kvm_run filled with MMIO request */
diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index f23b6a5..27d1b70 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -715,7 +715,8 @@  int kvm_arch_vcpu_ioctl_translate(struct kvm_vcpu *vcpu,
 int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
 					struct kvm_guest_debug *dbg)
 {
-	return -EINVAL;
+	vcpu->guest_debug = dbg->control;
+	return 0;
 }
 
 void kvmppc_decrementer_func(struct kvm_vcpu *vcpu)
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 529d10a..e63587d 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -725,6 +725,30 @@  static int kvmppc_hcall_impl_hv(unsigned long cmd)
 	return kvmppc_hcall_impl_hv_realmode(cmd);
 }
 
+static int kvmppc_emulate_debug_inst(struct kvm_run *run,
+					struct kvm_vcpu *vcpu)
+{
+	u32 last_inst;
+
+	if (kvmppc_get_last_inst(vcpu, INST_GENERIC, &last_inst) !=
+					EMULATE_DONE) {
+		/*
+		 * Fetch failed, so return to guest and
+		 * try executing it again.
+		 */
+		return RESUME_GUEST;
+	}
+
+	if (last_inst == KVMPPC_INST_SW_BREAKPOINT) {
+		run->exit_reason = KVM_EXIT_DEBUG;
+		run->debug.arch.address = kvmppc_get_pc(vcpu);
+		return RESUME_HOST;
+	} else {
+		kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
+		return RESUME_GUEST;
+	}
+}
+
 static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu,
 				 struct task_struct *tsk)
 {
@@ -807,12 +831,18 @@  static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu,
 		break;
 	/*
 	 * This occurs if the guest executes an illegal instruction.
-	 * We just generate a program interrupt to the guest, since
-	 * we don't emulate any guest instructions at this stage.
+	 * If the guest debug is disabled, generate a program interrupt
+	 * to the guest. If guest debug is enabled, we need to check
+	 * whether the instruction is a software breakpoint instruction.
+	 * Accordingly return to Guest or Host.
 	 */
 	case BOOK3S_INTERRUPT_H_EMUL_ASSIST:
-		kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
-		r = RESUME_GUEST;
+		if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) {
+			r = kvmppc_emulate_debug_inst(run, vcpu);
+		} else {
+			kvmppc_core_queue_program(vcpu, SRR1_PROGILL);
+			r = RESUME_GUEST;
+		}
 		break;
 	/*
 	 * This occurs if the guest (kernel or userspace), does something that
@@ -924,6 +954,9 @@  static int kvmppc_get_one_reg_hv(struct kvm_vcpu *vcpu, u64 id,
 	long int i;
 
 	switch (id) {
+	case KVM_REG_PPC_DEBUG_INST:
+		*val = get_reg_val(id, KVMPPC_INST_SW_BREAKPOINT);
+		break;
 	case KVM_REG_PPC_HIOR:
 		*val = get_reg_val(id, 0);
 		break;
diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index faffb27..6d73708 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -1319,6 +1319,9 @@  static int kvmppc_get_one_reg_pr(struct kvm_vcpu *vcpu, u64 id,
 	int r = 0;
 
 	switch (id) {
+	case KVM_REG_PPC_DEBUG_INST:
+		*val = get_reg_val(id, KVMPPC_INST_SW_BREAKPOINT);
+		break;
 	case KVM_REG_PPC_HIOR:
 		*val = get_reg_val(id, to_book3s(vcpu)->hior);
 		break;
diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
index e96b50d..005222b 100644
--- a/arch/powerpc/kvm/emulate.c
+++ b/arch/powerpc/kvm/emulate.c
@@ -274,6 +274,21 @@  int kvmppc_emulate_instruction(struct kvm_run *run, struct kvm_vcpu *vcpu)
 		}
 		break;
 
+	case 0:
+		/*
+		 * Instruction with primary opcode 0. Based on PowerISA
+		 * these are illegal instructions.
+		 */
+		if (inst == KVMPPC_INST_SW_BREAKPOINT) {
+			run->exit_reason = KVM_EXIT_DEBUG;
+			run->debug.arch.address = kvmppc_get_pc(vcpu);
+			emulated = EMULATE_EXIT_USER;
+			advance = 0;
+		} else
+			emulated = EMULATE_FAIL;
+
+		break;
+
 	default:
 		emulated = EMULATE_FAIL;
 	}