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

Jeremy Fitzhardinge
2009-03-13T07:38:17Z

Jaswinder Singh Rajput wrote:
> On Wed, 2009-03-11 at 14:13 +0100, Ingo Molnar wrote:
>
>> * Ingo Molnar <mingo@elte.hu> wrote:
>>
>>
>>> * Jaswinder Singh Rajput <jaswinder@kernel.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