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>

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 31ac8e6..116b583 100644 (file)
--- 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 (file)
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>

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 9702754..7d56474 100644 (file)
--- 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 31c6a60..c6f2a3c 100644 (file)
--- 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);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 902d9da..1ba3b7d 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -55,9 +55,6 @@
 #include <linux/irqbypass.h>
 #include <trace/events/kvm.h>
 
-#define CREATE_TRACE_POINTS
-#include "trace.h"
-
 #include <asm/debugreg.h>
 #include <asm/msr.h>
 #include <asm/desc.h>
@@ -68,6 +65,9 @@
 #include <asm/div64.h>
 #include <asm/irq_remapping.h>
 
+#define CREATE_TRACE_POINTS
+#include "trace.h"
+
 #define MAX_IO_MSRS 256
 #define KVM_MAX_MCE_BANKS 32
 #define KVM_MCE_CAP_SUPPORTED (MCG_CTL_P | MCG_SER_P)