x86/fpu: Add tracepoints to dump FPU state at key points

I've been carrying this patch around for a bit and it's helped me
solve at least a couple FPU-related bugs.  In addition to using
it for debugging, I also drug it out because using AVX (and
AVX2/AVX-512) can have serious power consequences for a modern
core.  It's very important to be able to figure out who is using
it.

It's also insanely useful to go out and see who is using a given
feature, like MPX or Memory Protection Keys.  If you, for
instance, want to find all processes using protection keys, you
can do:

	echo 'xfeatures & 0x200' > filter

Since 0x200 is the protection keys feature bit.

Note that this touches the KVM code.  KVM did a CREATE_TRACE_POINTS
and then included a bunch of random headers.  If anyone one of
those included other tracepoints, it would have defined the *OTHER*
tracepoints.  That's bogus, so move it to the right place.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160601174220.3CDFB90E@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2 files changed, 124 insertions, 0 deletions

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 31ac8e6..116b583 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -18,6 +18,7 @@
 #include <asm/fpu/api.h>
 #include <asm/fpu/xstate.h>
 #include <asm/cpufeature.h>
+#include <asm/trace/fpu.h>
 
 /*
  * High level FPU state handling functions:
@@ -524,6 +525,7 @@ static inline void __fpregs_deactivate(struct fpu *fpu)
 
 	fpu->fpregs_active = 0;
 	this_cpu_write(fpu_fpregs_owner_ctx, NULL);
+	trace_x86_fpu_regs_deactivated(fpu);
 }
 
 /* Must be paired with a 'clts' (fpregs_activate_hw()) before! */
@@ -533,6 +535,7 @@ static inline void __fpregs_activate(struct fpu *fpu)
 
 	fpu->fpregs_active = 1;
 	this_cpu_write(fpu_fpregs_owner_ctx, fpu);
+	trace_x86_fpu_regs_activated(fpu);
 }
 
 /*
@@ -604,11 +607,13 @@ switch_fpu_prepare(struct fpu *old_fpu, struct fpu *new_fpu, int cpu)
 
 		/* But leave fpu_fpregs_owner_ctx! */
 		old_fpu->fpregs_active = 0;
+		trace_x86_fpu_regs_deactivated(old_fpu);
 
 		/* Don't change CR0.TS if we just switch! */
 		if (fpu.preload) {
 			new_fpu->counter++;
 			__fpregs_activate(new_fpu);
+			trace_x86_fpu_regs_activated(new_fpu);
 			prefetch(&new_fpu->state);
 		} else {
 			__fpregs_deactivate_hw();
diff --git a/arch/x86/include/asm/trace/fpu.h b/arch/x86/include/asm/trace/fpu.h
new file mode 100644
index 0000000..9217ab1
--- /dev/null
+++ b/arch/x86/include/asm/trace/fpu.h
@@ -0,0 +1,119 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM x86_fpu
+
+#if !defined(_TRACE_FPU_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_FPU_H
+
+#include <linux/tracepoint.h>
+
+DECLARE_EVENT_CLASS(x86_fpu,
+	TP_PROTO(struct fpu *fpu),
+	TP_ARGS(fpu),
+
+	TP_STRUCT__entry(
+		__field(struct fpu *, fpu)
+		__field(bool, fpregs_active)
+		__field(bool, fpstate_active)
+		__field(int, counter)
+		__field(u64, xfeatures)
+		__field(u64, xcomp_bv)
+		),
+
+	TP_fast_assign(
+		__entry->fpu		= fpu;
+		__entry->fpregs_active	= fpu->fpregs_active;
+		__entry->fpstate_active	= fpu->fpstate_active;
+		__entry->counter	= fpu->counter;
+		if (boot_cpu_has(X86_FEATURE_OSXSAVE)) {
+			__entry->xfeatures = fpu->state.xsave.header.xfeatures;
+			__entry->xcomp_bv  = fpu->state.xsave.header.xcomp_bv;
+		}
+	),
+	TP_printk("x86/fpu: %p fpregs_active: %d fpstate_active: %d counter: %d xfeatures: %llx xcomp_bv: %llx",
+			__entry->fpu,
+			__entry->fpregs_active,
+			__entry->fpstate_active,
+			__entry->counter,
+			__entry->xfeatures,
+			__entry->xcomp_bv
+	)
+);
+
+DEFINE_EVENT(x86_fpu, x86_fpu_state,
+	TP_PROTO(struct fpu *fpu),
+	TP_ARGS(fpu)
+);
+
+DEFINE_EVENT(x86_fpu, x86_fpu_before_save,
+	TP_PROTO(struct fpu *fpu),
+	TP_ARGS(fpu)
+);
+
+DEFINE_EVENT(x86_fpu, x86_fpu_after_save,
+	TP_PROTO(struct fpu *fpu),
+	TP_ARGS(fpu)
+);
+
+DEFINE_EVENT(x86_fpu, x86_fpu_before_restore,
+	TP_PROTO(struct fpu *fpu),
+	TP_ARGS(fpu)
+);
+
+DEFINE_EVENT(x86_fpu, x86_fpu_after_restore,
+	TP_PROTO(struct fpu *fpu),
+	TP_ARGS(fpu)
+);
+
+DEFINE_EVENT(x86_fpu, x86_fpu_regs_activated,
+	TP_PROTO(struct fpu *fpu),
+	TP_ARGS(fpu)
+);
+
+DEFINE_EVENT(x86_fpu, x86_fpu_regs_deactivated,
+	TP_PROTO(struct fpu *fpu),
+	TP_ARGS(fpu)
+);
+
+DEFINE_EVENT(x86_fpu, x86_fpu_activate_state,
+	TP_PROTO(struct fpu *fpu),
+	TP_ARGS(fpu)
+);
+
+DEFINE_EVENT(x86_fpu, x86_fpu_deactivate_state,
+	TP_PROTO(struct fpu *fpu),
+	TP_ARGS(fpu)
+);
+
+DEFINE_EVENT(x86_fpu, x86_fpu_init_state,
+	TP_PROTO(struct fpu *fpu),
+	TP_ARGS(fpu)
+);
+
+DEFINE_EVENT(x86_fpu, x86_fpu_dropped,
+	TP_PROTO(struct fpu *fpu),
+	TP_ARGS(fpu)
+);
+
+DEFINE_EVENT(x86_fpu, x86_fpu_copy_src,
+	TP_PROTO(struct fpu *fpu),
+	TP_ARGS(fpu)
+);
+
+DEFINE_EVENT(x86_fpu, x86_fpu_copy_dst,
+	TP_PROTO(struct fpu *fpu),
+	TP_ARGS(fpu)
+);
+
+DEFINE_EVENT(x86_fpu, x86_fpu_xstate_check_failed,
+	TP_PROTO(struct fpu *fpu),
+	TP_ARGS(fpu)
+);
+
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH asm/trace/
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_FILE fpu
+#endif /* _TRACE_FPU_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>