KVM: Trace emulated instructions

Log emulated instructions in ftrace, especially if they failed.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/trace.h

@@ -603,6 +603,92 @@ TRACE_EVENT(kvm_skinit,
 		  __entry->rip, __entry->slb)
 );
 
+#define __print_insn(insn, ilen) ({		                 \
+	int i;							 \
+	const char *ret = p->buffer + p->len;			 \
+								 \
+	for (i = 0; i < ilen; ++i)				 \
+		trace_seq_printf(p, " %02x", insn[i]);		 \
+	trace_seq_printf(p, "%c", 0);				 \
+	ret;							 \
+	})
+
+#define KVM_EMUL_INSN_F_CR0_PE (1 << 0)
+#define KVM_EMUL_INSN_F_EFL_VM (1 << 1)
+#define KVM_EMUL_INSN_F_CS_D   (1 << 2)
+#define KVM_EMUL_INSN_F_CS_L   (1 << 3)
+
+#define kvm_trace_symbol_emul_flags	                  \
+	{ 0,   			    "real" },		  \
+	{ KVM_EMUL_INSN_F_CR0_PE			  \
+	  | KVM_EMUL_INSN_F_EFL_VM, "vm16" },		  \
+	{ KVM_EMUL_INSN_F_CR0_PE,   "prot16" },		  \
+	{ KVM_EMUL_INSN_F_CR0_PE			  \
+	  | KVM_EMUL_INSN_F_CS_D,   "prot32" },		  \
+	{ KVM_EMUL_INSN_F_CR0_PE			  \
+	  | KVM_EMUL_INSN_F_CS_L,   "prot64" }
+
+#define kei_decode_mode(mode) ({			\
+	u8 flags = 0xff;				\
+	switch (mode) {					\
+	case X86EMUL_MODE_REAL:				\
+		flags = 0;				\
+		break;					\
+	case X86EMUL_MODE_VM86:				\
+		flags = KVM_EMUL_INSN_F_EFL_VM;		\
+		break;					\
+	case X86EMUL_MODE_PROT16:			\
+		flags = KVM_EMUL_INSN_F_CR0_PE;		\
+		break;					\
+	case X86EMUL_MODE_PROT32:			\
+		flags = KVM_EMUL_INSN_F_CR0_PE		\
+			| KVM_EMUL_INSN_F_CS_D;		\
+		break;					\
+	case X86EMUL_MODE_PROT64:			\
+		flags = KVM_EMUL_INSN_F_CR0_PE		\
+			| KVM_EMUL_INSN_F_CS_L;		\
+		break;					\
+	}						\
+	flags;						\
+	})
+
+TRACE_EVENT(kvm_emulate_insn,
+	TP_PROTO(struct kvm_vcpu *vcpu, __u8 failed),
+	TP_ARGS(vcpu, failed),
+
+	TP_STRUCT__entry(
+		__field(    __u64, rip                       )
+		__field(    __u32, csbase                    )
+		__field(    __u8,  len                       )
+		__array(    __u8,  insn,    15	             )
+		__field(    __u8,  flags       	   	     )
+		__field(    __u8,  failed                    )
+		),
+
+	TP_fast_assign(
+		__entry->rip = vcpu->arch.emulate_ctxt.decode.fetch.start;
+		__entry->csbase = kvm_x86_ops->get_segment_base(vcpu, VCPU_SREG_CS);
+		__entry->len = vcpu->arch.emulate_ctxt.decode.eip
+			       - vcpu->arch.emulate_ctxt.decode.fetch.start;
+		memcpy(__entry->insn,
+		       vcpu->arch.emulate_ctxt.decode.fetch.data,
+		       15);
+		__entry->flags = kei_decode_mode(vcpu->arch.emulate_ctxt.mode);
+		__entry->failed = failed;
+		),
+
+	TP_printk("%x:%llx:%s (%s)%s",
+		  __entry->csbase, __entry->rip,
+		  __print_insn(__entry->insn, __entry->len),
+		  __print_symbolic(__entry->flags,
+				   kvm_trace_symbol_emul_flags),
+		  __entry->failed ? " failed" : ""
+		)
+	);
+
+#define trace_kvm_emulate_insn_start(vcpu) trace_kvm_emulate_insn(vcpu, 0)
+#define trace_kvm_emulate_insn_failed(vcpu) trace_kvm_emulate_insn(vcpu, 1)
+
 #endif /* _TRACE_KVM_H */
 
 #undef TRACE_INCLUDE_PATH

arch/x86/kvm/x86.c

@@ -3718,6 +3718,7 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
 			? X86EMUL_MODE_PROT32 : X86EMUL_MODE_PROT16;
 
 		r = x86_decode_insn(&vcpu->arch.emulate_ctxt, &emulate_ops);
+		trace_kvm_emulate_insn_start(vcpu);
 
 		/* Only allow emulation of specific instructions on #UD
 		 * (namely VMMCALL, sysenter, sysexit, syscall)*/
@@ -3750,6 +3751,7 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
 		++vcpu->stat.insn_emulation;
 		if (r)  {
 			++vcpu->stat.insn_emulation_fail;
+			trace_kvm_emulate_insn_failed(vcpu);
 			if (kvm_mmu_unprotect_page_virt(vcpu, cr2))
 				return EMULATE_DONE;
 			return EMULATE_FAIL;
@@ -3786,6 +3788,8 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
 		if (kvm_mmu_unprotect_page_virt(vcpu, cr2))
 			goto done;
 		if (!vcpu->mmio_needed) {
+			++vcpu->stat.insn_emulation_fail;
+			trace_kvm_emulate_insn_failed(vcpu);
 			kvm_report_emulation_failure(vcpu, "mmio");
 			return EMULATE_FAIL;
 		}