linux-kernel - Re: [git-pull -tip V2] x86: cpu architecture debug code

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Date:	Fri, 13 Mar 2009 00:37:57 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Jaswinder Singh Rajput <jaswinder@...nel.org>
CC:	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [git-pull -tip V2] x86: cpu architecture debug code

Jaswinder Singh Rajput wrote:
> On Wed, 2009-03-11 at 14:13 +0100, Ingo Molnar wrote:
>   
>> * Ingo Molnar <mingo@...e.hu> wrote:
>>
>>     
>>> * Jaswinder Singh Rajput <jaswinder@...nel.org> wrote:
>>>
>>>       
>>>> @@ -472,7 +473,7 @@ static void print_dt(void *seq)
>>>>  	print_desc_ptr("GDT", seq, dt);
>>>>  
>>>>  	/* LDT */
>>>> -	store_ldt(ldt);
>>>> +	asm volatile("sldt %0" : "=m" (ldt));
>>>>         
>>> this is still wrong.
>>>       
>> As i pointed it out before, we should not open-code an assembly 
>> primitive - especially since store_ldt() is available in 
>> arch/x86/include/asm/desc.h.
>>
>> True, that primitive is not available on CONFIG_PARAVIRT, but 
>> that is a bug: the fix is to move the store_ldt() definition 
>> outside the CONFIG_PARAVIRT section in desc.h, not to hack 
>> around the problem by open-coding assembly code.
>>
>> I.e. dont let an uncleanliness and incomplete primitive spread 
>> to other code. Fix the primitive and remove the uncleanliness 
>> that way.
>>
>>     
>
> The following changes since commit 259ef6fcea4046fe24495b1e3631c1b905c531c1:
>   Jaswinder Singh Rajput (1):
>         x86: cpu architecture debug code
>
> are available in the git repository at:
>
>   git://git.kernel.org/pub/scm/linux/kernel/git/jaswinder/linux-2.6-tip-cpu.git master
>
> Jaswinder Singh Rajput (2):
>       x86: cpu_debug.c cleanup
>       x86: move store_ldt outside the CONFIG_PARAVIRT section
>
>  arch/x86/include/asm/desc.h     |    3 ++-
>  arch/x86/kernel/cpu/cpu_debug.c |    3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
>
> Complete diff:
> diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h
> index dc27705..ceb17cc 100644
> --- a/arch/x86/include/asm/desc.h
> +++ b/arch/x86/include/asm/desc.h
> @@ -91,7 +91,6 @@ static inline int desc_empty(const void *ptr)
>  #define store_gdt(dtr) native_store_gdt(dtr)
>  #define store_idt(dtr) native_store_idt(dtr)
>  #define store_tr(tr) (tr = native_store_tr())
> -#define store_ldt(ldt) asm("sldt %0":"=m" (ldt))
>  
>  #define load_TLS(t, cpu) native_load_tls(t, cpu)
>  #define set_ldt native_set_ldt
> @@ -112,6 +111,8 @@ static inline void paravirt_free_ldt(struct desc_struct *ldt, unsigned entries)
>  }
>  #endif	/* CONFIG_PARAVIRT */
>  
> +#define store_ldt(ldt) asm("sldt %0":"=m" (ldt))
> +
>  static inline void native_write_idt_entry(gate_desc *idt, int entry,
>  					  const gate_desc *gate)
>  {
> diff --git a/arch/x86/kernel/cpu/cpu_debug.c b/arch/x86/kernel/cpu/cpu_debug.c
> index 0bdf4da..9abbcbd 100755
> --- a/arch/x86/kernel/cpu/cpu_debug.c
> +++ b/arch/x86/kernel/cpu/cpu_debug.c
> @@ -23,6 +23,7 @@
>  #include <linux/smp.h>
>  
>  #include <asm/cpu_debug.h>
> +#include <asm/paravirt.h>
>   
This shouldn't be necessary.  asm/desc.h should pull it in if it needs it.

    J
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