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Commit d1898b73 authored by Dave Hansen's avatar Dave Hansen Committed by Ingo Molnar
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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: default avatarDave 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: default avatarIngo Molnar <mingo@kernel.org>
parent c8ae067f

arch/x86/include/asm/fpu/internal.h

+5 −0
Original line number Diff line number Diff line
@@ -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();

arch/x86/include/asm/trace/fpu.h

0 → 100644
+119 −0
Original line number Diff line number Diff line 
#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>

arch/x86/kernel/fpu/core.c

+18 −0
Original line number Diff line number Diff line
@@ -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();

}

arch/x86/kernel/fpu/signal.c

+3 −0
Original line number Diff line number Diff line
@@ -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);

arch/x86/kvm/x86.c

+3 −3
Original line number Diff line number Diff line
@@ -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)