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, 21 insertions, 0 deletions

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 97027545a72d..7d564742e499 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -12,6 +12,9 @@
 
 #include <linux/hardirq.h>
 
+#define CREATE_TRACE_POINTS
+#include <asm/trace/fpu.h>
+
 /*
  * Represents the initial FPU state. It's mostly (but not completely) zeroes,
  * depending on the FPU hardware format:
@@ -192,6 +195,7 @@ void fpu__save(struct fpu *fpu)
         WARN_ON_FPU(fpu != &current->thread.fpu);
 
         preempt_disable();
+        trace_x86_fpu_before_save(fpu);
         if (fpu->fpregs_active) {
                 if (!copy_fpregs_to_fpstate(fpu)) {
                         if (use_eager_fpu())
@@ -200,6 +204,7 @@ void fpu__save(struct fpu *fpu)
                                 fpregs_deactivate(fpu);
                 }
         }
+        trace_x86_fpu_after_save(fpu);
         preempt_enable();
 }
 EXPORT_SYMBOL_GPL(fpu__save);
@@ -275,6 +280,9 @@ int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
         }
         preempt_enable();
 
+        trace_x86_fpu_copy_src(src_fpu);
+        trace_x86_fpu_copy_dst(dst_fpu);
+
         return 0;
 }
 
@@ -288,7 +296,9 @@ void fpu__activate_curr(struct fpu *fpu)
 
         if (!fpu->fpstate_active) {
                 fpstate_init(&fpu->state);
+                trace_x86_fpu_init_state(fpu);
 
+                trace_x86_fpu_activate_state(fpu);
                 /* Safe to do for the current task: */
                 fpu->fpstate_active = 1;
         }
@@ -314,7 +324,9 @@ void fpu__activate_fpstate_read(struct fpu *fpu)
         } else {
                 if (!fpu->fpstate_active) {
                         fpstate_init(&fpu->state);
+                        trace_x86_fpu_init_state(fpu);
 
+                        trace_x86_fpu_activate_state(fpu);
                         /* Safe to do for current and for stopped child tasks: */
                         fpu->fpstate_active = 1;
                 }
@@ -347,7 +359,9 @@ void fpu__activate_fpstate_write(struct fpu *fpu)
                 fpu->last_cpu = -1;
         } else {
                 fpstate_init(&fpu->state);
+                trace_x86_fpu_init_state(fpu);
 
+                trace_x86_fpu_activate_state(fpu);
                 /* Safe to do for stopped child tasks: */
                 fpu->fpstate_active = 1;
         }
@@ -432,9 +446,11 @@ void fpu__restore(struct fpu *fpu)
 
         /* Avoid __kernel_fpu_begin() right after fpregs_activate() */
         kernel_fpu_disable();
+        trace_x86_fpu_before_restore(fpu);
         fpregs_activate(fpu);
         copy_kernel_to_fpregs(&fpu->state);
         fpu->counter++;
+        trace_x86_fpu_after_restore(fpu);
         kernel_fpu_enable();
 }
 EXPORT_SYMBOL_GPL(fpu__restore);
@@ -463,6 +479,8 @@ void fpu__drop(struct fpu *fpu)
 
         fpu->fpstate_active = 0;
 
+        trace_x86_fpu_dropped(fpu);
+
         preempt_enable();
 }
 
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 31c6a60505e6..c6f2a3cee2c2 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -10,6 +10,7 @@
 #include <asm/fpu/regset.h>
 
 #include <asm/sigframe.h>
+#include <asm/trace/fpu.h>
 
 static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32;
 
@@ -282,6 +283,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
                          */
                         state_size = sizeof(struct fxregs_state);
                         fx_only = 1;
+                        trace_x86_fpu_xstate_check_failed(fpu);
                 } else {
                         state_size = fx_sw_user.xstate_size;
                         xfeatures = fx_sw_user.xfeatures;
@@ -311,6 +313,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
                 if (__copy_from_user(&fpu->state.xsave, buf_fx, state_size) ||
                     __copy_from_user(&env, buf, sizeof(env))) {
                         fpstate_init(&fpu->state);
+                        trace_x86_fpu_init_state(fpu);
                         err = -1;
                 } else {
                         sanitize_restored_xstate(tsk, &env, xfeatures, fx_only);