[PATCH 1/4 v2] Added ONE_REG interface for debug instruction

[Bharat Bhushan <r65777@xxxxxxxxxxxxx>]

This patch adds the one_reg interface to get the special instruction
to be used for setting software breakpoint from userspace.

Signed-off-by: Bharat Bhushan <bharat.bhushan@xxxxxxxxxxxxx>
---
v2:
 - Corrected trap "tw" always opcode.

 Documentation/virtual/kvm/api.txt     |    1 +
 arch/powerpc/include/asm/kvm_book3s.h |    2 ++
 arch/powerpc/include/asm/kvm_booke.h  |    2 ++
 arch/powerpc/include/uapi/asm/kvm.h   |    4 ++++
 arch/powerpc/kvm/book3s.c             |    6 ++++++
 arch/powerpc/kvm/booke.c              |    6 ++++++
 6 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index cce500a..dbfcc04 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1766,6 +1766,7 @@ registers, find a list below:
   PPC   | KVM_REG_PPC_TSR	| 32
   PPC   | KVM_REG_PPC_OR_TSR	| 32
   PPC   | KVM_REG_PPC_CLEAR_TSR	| 32
+  PPC   | KVM_REG_PPC_DEBUG_INST| 32
 
 4.69 KVM_GET_ONE_REG
 
diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
index 5a56e1c..bc81842 100644
--- a/arch/powerpc/include/asm/kvm_book3s.h
+++ b/arch/powerpc/include/asm/kvm_book3s.h
@@ -458,6 +458,8 @@ static inline bool kvmppc_critical_section(struct kvm_vcpu *vcpu)
 #define OSI_SC_MAGIC_R4			0x77810F9B
 
 #define INS_DCBZ			0x7c0007ec
+/* TO = 31 for unconditional trap */
+#define INS_TW				0x7fe00008
 
 /* LPIDs we support with this build -- runtime limit may be lower */
 #define KVMPPC_NR_LPIDS			(LPID_RSVD + 1)
diff --git a/arch/powerpc/include/asm/kvm_booke.h b/arch/powerpc/include/asm/kvm_booke.h
index b7cd335..d3c1eb3 100644
--- a/arch/powerpc/include/asm/kvm_booke.h
+++ b/arch/powerpc/include/asm/kvm_booke.h
@@ -26,6 +26,8 @@
 /* LPIDs we support with this build -- runtime limit may be lower */
 #define KVMPPC_NR_LPIDS                        64
 
+#define KVMPPC_INST_EHPRIV	0x7c00021c
+
 static inline void kvmppc_set_gpr(struct kvm_vcpu *vcpu, int num, ulong val)
 {
 	vcpu->arch.gpr[num] = val;
diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h
index ef072b1..c2ff99c 100644
--- a/arch/powerpc/include/uapi/asm/kvm.h
+++ b/arch/powerpc/include/uapi/asm/kvm.h
@@ -422,4 +422,8 @@ struct kvm_get_htab_header {
 #define KVM_REG_PPC_CLEAR_TSR	(KVM_REG_PPC | KVM_REG_SIZE_U32 | 0x88)
 #define KVM_REG_PPC_TCR		(KVM_REG_PPC | KVM_REG_SIZE_U32 | 0x89)
 #define KVM_REG_PPC_TSR		(KVM_REG_PPC | KVM_REG_SIZE_U32 | 0x8a)
+
+/* Debugging: Special instruction for software breakpoint */
+#define KVM_REG_PPC_DEBUG_INST	(KVM_REG_PPC | KVM_REG_SIZE_U32 | 0x8b)
+
 #endif /* __LINUX_KVM_POWERPC_H */
diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index a4b6452..975a401 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -530,6 +530,12 @@ int kvm_vcpu_ioctl_get_one_reg(struct kvm_vcpu *vcpu, struct kvm_one_reg *reg)
 			val = get_reg_val(reg->id, vcpu->arch.vscr.u[3]);
 			break;
 #endif /* CONFIG_ALTIVEC */
+		case KVM_REG_PPC_DEBUG_INST: {
+			u32 opcode = INS_TW;
+			r = copy_to_user((u32 __user *)(long)reg->addr,
+					 &opcode, sizeof(u32));
+			break;
+		}
 		default:
 			r = -EINVAL;
 			break;
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 8b553c0..a41cd6d 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -1448,6 +1448,12 @@ int kvm_vcpu_ioctl_get_one_reg(struct kvm_vcpu *vcpu, struct kvm_one_reg *reg)
 	case KVM_REG_PPC_TSR:
 		r = put_user(vcpu->arch.tsr, (u32 __user *)(long)reg->addr);
 		break;
+	case KVM_REG_PPC_DEBUG_INST: {
+		u32 opcode = KVMPPC_INST_EHPRIV;
+		r = copy_to_user((u32 __user *)(long)reg->addr,
+				 &opcode, sizeof(u32));
+		break;
+	}
 	default:
 		break;
 	}
-- 
1.7.0.4


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