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authorJames Hogan <james.hogan@imgtec.com>2017-03-14 10:15:40 +0000
committerJames Hogan <james.hogan@imgtec.com>2017-03-28 14:54:00 +0100
commitedec9d7bdc4eb3845ec7a3f9610f0d54a7152e90 (patch)
tree89b4d3c4b8c0f549d9aa9c4f379142bce3e85bed
parentf4474d50c7d483dd4432d5b0891b0bb9ad0eefc9 (diff)
downloadlinux-edec9d7bdc4eb3845ec7a3f9610f0d54a7152e90.tar.bz2
KVM: MIPS/VZ: Trace guest mode changes
Create a trace event for guest mode changes, and enable VZ's GuestCtl0.MC bit after the trace event is enabled to trap all guest mode changes. The MC bit causes Guest Hardware Field Change (GHFC) exceptions whenever a guest mode change occurs (such as an exception entry or return from exception), so we need to handle this exception now. The MC bit is only enabled when restoring register state, so enabling the trace event won't take immediate effect. Tracing guest mode changes can be particularly handy when trying to work out what a guest OS gets up to before something goes wrong, especially if the problem occurs as a result of some previous guest userland exception which would otherwise be invisible in the trace. Signed-off-by: James Hogan <james.hogan@imgtec.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: "Radim Krčmář" <rkrcmar@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org
-rw-r--r--arch/mips/kvm/mips.c13
-rw-r--r--arch/mips/kvm/trace.h37
-rw-r--r--arch/mips/kvm/vz.c21
3 files changed, 69 insertions, 2 deletions
diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index e8ddb128b8ad..1fc6fef463db 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -76,6 +76,19 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
{NULL}
};
+bool kvm_trace_guest_mode_change;
+
+int kvm_guest_mode_change_trace_reg(void)
+{
+ kvm_trace_guest_mode_change = 1;
+ return 0;
+}
+
+void kvm_guest_mode_change_trace_unreg(void)
+{
+ kvm_trace_guest_mode_change = 0;
+}
+
/*
* XXXKYMA: We are simulatoring a processor that has the WII bit set in
* Config7, so we are "runnable" if interrupts are pending
diff --git a/arch/mips/kvm/trace.h b/arch/mips/kvm/trace.h
index affde8a2c584..a8c7fd7bf6d2 100644
--- a/arch/mips/kvm/trace.h
+++ b/arch/mips/kvm/trace.h
@@ -18,6 +18,13 @@
#define TRACE_INCLUDE_FILE trace
/*
+ * arch/mips/kvm/mips.c
+ */
+extern bool kvm_trace_guest_mode_change;
+int kvm_guest_mode_change_trace_reg(void);
+void kvm_guest_mode_change_trace_unreg(void);
+
+/*
* Tracepoints for VM enters
*/
DECLARE_EVENT_CLASS(kvm_transition,
@@ -303,6 +310,36 @@ TRACE_EVENT(kvm_guestid_change,
__entry->guestid)
);
+TRACE_EVENT_FN(kvm_guest_mode_change,
+ TP_PROTO(struct kvm_vcpu *vcpu),
+ TP_ARGS(vcpu),
+ TP_STRUCT__entry(
+ __field(unsigned long, epc)
+ __field(unsigned long, pc)
+ __field(unsigned long, badvaddr)
+ __field(unsigned int, status)
+ __field(unsigned int, cause)
+ ),
+
+ TP_fast_assign(
+ __entry->epc = kvm_read_c0_guest_epc(vcpu->arch.cop0);
+ __entry->pc = vcpu->arch.pc;
+ __entry->badvaddr = kvm_read_c0_guest_badvaddr(vcpu->arch.cop0);
+ __entry->status = kvm_read_c0_guest_status(vcpu->arch.cop0);
+ __entry->cause = kvm_read_c0_guest_cause(vcpu->arch.cop0);
+ ),
+
+ TP_printk("EPC: 0x%08lx PC: 0x%08lx Status: 0x%08x Cause: 0x%08x BadVAddr: 0x%08lx",
+ __entry->epc,
+ __entry->pc,
+ __entry->status,
+ __entry->cause,
+ __entry->badvaddr),
+
+ kvm_guest_mode_change_trace_reg,
+ kvm_guest_mode_change_trace_unreg
+);
+
#endif /* _TRACE_KVM_H */
/* This part must be outside protection */
diff --git a/arch/mips/kvm/vz.c b/arch/mips/kvm/vz.c
index 44dad9ae5d02..33bb8c6e1b05 100644
--- a/arch/mips/kvm/vz.c
+++ b/arch/mips/kvm/vz.c
@@ -1322,6 +1322,18 @@ static enum emulation_result kvm_trap_vz_handle_gsfc(u32 cause, u32 *opc,
return er;
}
+static enum emulation_result kvm_trap_vz_handle_ghfc(u32 cause, u32 *opc,
+ struct kvm_vcpu *vcpu)
+{
+ /*
+ * Presumably this is due to MC (guest mode change), so lets trace some
+ * relevant info.
+ */
+ trace_kvm_guest_mode_change(vcpu);
+
+ return EMULATE_DONE;
+}
+
static enum emulation_result kvm_trap_vz_handle_hc(u32 cause, u32 *opc,
struct kvm_vcpu *vcpu)
{
@@ -1407,8 +1419,7 @@ static int kvm_trap_vz_handle_guest_exit(struct kvm_vcpu *vcpu)
break;
case MIPS_GCTL0_GEXC_GHFC:
++vcpu->stat.vz_ghfc_exits;
- er = kvm_trap_vz_no_handler_guest_exit(gexccode, cause, opc,
- vcpu);
+ er = kvm_trap_vz_handle_ghfc(cause, opc, vcpu);
break;
case MIPS_GCTL0_GEXC_GPA:
++vcpu->stat.vz_gpa_exits;
@@ -2459,6 +2470,12 @@ static int kvm_vz_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
*/
kvm_vz_restore_timer(vcpu);
+ /* Set MC bit if we want to trace guest mode changes */
+ if (kvm_trace_guest_mode_change)
+ set_c0_guestctl0(MIPS_GCTL0_MC);
+ else
+ clear_c0_guestctl0(MIPS_GCTL0_MC);
+
/* Don't bother restoring registers multiple times unless necessary */
if (!all)
return 0;