linux-kernel - Re: [RFC][PATCH v8 2/3] trace,x86: add x86 irq vector tracepoints

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Date:	Fri, 01 Feb 2013 16:03:34 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Seiji Aguchi <seiji.aguchi@....com>
Cc:	"x86@...nel.org" <x86@...nel.org>,
	"H. Peter Anvin (hpa@...or.com)" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Thomas Gleixner (tglx@...utronix.de)" <tglx@...utronix.de>,
	"'mingo@...e.hu' (mingo@...e.hu)" <mingo@...e.hu>,
	"Borislav Petkov (bp@...en8.de)" <bp@...en8.de>,
	Satoru Moriya <satoru.moriya@....com>,
	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	"linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
	"Luck, Tony (tony.luck@...el.com)" <tony.luck@...el.com>
Subject: Re: [RFC][PATCH v8 2/3] trace,x86: add x86 irq vector tracepoints

On Mon, 2013-01-21 at 22:14 +0000, Seiji Aguchi wrote:

> --- /dev/null
> +++ b/arch/x86/kernel/tracepoint.c
> @@ -0,0 +1,61 @@
> +/*
> + * Code for supporting irq vector tracepoints.
> + *
> + * Copyright (C) 2013 Seiji Aguchi <seiji.aguchi@....com>
> + *
> + */
> +#include <asm/hw_irq.h>
> +#include <asm/desc.h>
> +
> +static struct desc_ptr trace_idt_descr = { NR_VECTORS * 16 - 1,
> +				    (unsigned long) trace_idt_table };
> +
> +#ifndef CONFIG_X86_64
> +gate_desc trace_idt_table[NR_VECTORS] __page_aligned_data
> +					= { { { { 0, 0 } } }, };
> +#endif
> +
> +static struct desc_ptr orig_idt_descr[NR_CPUS];

BTW, this should be:

static DEFINE_PER_CPU(struct desc_ptr, orig_idt_descr);

And look at the patch I made about the NMI/DEBUG trap handling to see
how to use it.

Thanks,

-- Steve

> +static int trace_irq_vector_refcount;
> +
> +static void switch_to_trace_idt(void *arg)
> +{
> +	store_idt(&orig_idt_descr[smp_processor_id()]);
> +	load_idt(&trace_idt_descr);
> +
> +	return;
> +}
> +
> +static void restore_original_idt(void *arg)
> +{
> +	if (orig_idt_descr[smp_processor_id()].address) {
> +		load_idt(&orig_idt_descr[smp_processor_id()]);
> +		memset(&orig_idt_descr[smp_processor_id()], 0,
> +		       sizeof(struct desc_ptr));
> +	}
> +
> +	return;
> +}
> +
> +void trace_irq_vector_regfunc(void)
> +{
> +	if (!trace_irq_vector_refcount) {
> +		smp_call_function(switch_to_trace_idt, NULL, 0);
> +		local_irq_disable();
> +		switch_to_trace_idt(NULL);
> +		local_irq_enable();
> +	}
> +	trace_irq_vector_refcount++;
> +}
> +
> +void trace_irq_vector_unregfunc(void)
> +{
> +	trace_irq_vector_refcount--;
> +	if (!trace_irq_vector_refcount) {
> +		smp_call_function(restore_original_idt, NULL, 0);
> +		local_irq_disable();
> +		restore_original_idt(NULL);
> +		local_irq_enable();
> +	}
> +}
> +
> diff --git a/include/xen/events.h b/include/xen/events.h
> index c6bfe01..9216d07 100644
> --- a/include/xen/events.h
> +++ b/include/xen/events.h
> @@ -76,6 +76,9 @@ unsigned irq_from_evtchn(unsigned int evtchn);
>  
>  /* Xen HVM evtchn vector callback */
>  void xen_hvm_callback_vector(void);
> +#ifdef CONFIG_TRACING
> +#define trace_xen_hvm_callback_vector xen_hvm_callback_vector
> +#endif
>  extern int xen_have_vector_callback;
>  int xen_set_callback_via(uint64_t via);
>  void xen_evtchn_do_upcall(struct pt_regs *regs);


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