Re: [Xen-devel] [PATCH for-next 2/3] xen/x86: Introduce static inline wrappers for l{idt, gdt, ldt, tr}()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.10.17 at 18:13, <andrew.cooper3@xxxxxxxxxx> wrote:
> The triple-fault reboot method stays as is, to avoid the int3 possibly getting
> moved relative to the lidt.

Aren't asm volatile()s ordered wrt to one another?

> --- a/xen/include/asm-x86/desc.h
> +++ b/xen/include/asm-x86/desc.h
> @@ -197,6 +197,26 @@ DECLARE_PER_CPU(struct desc_struct *, compat_gdt_table);
>  
>  extern void load_TR(void);
>  
> +static inline void lgdt(const struct desc_ptr *gdtr)
> +{
> +    asm volatile ("lgdt %0" :: "m" (*gdtr));
> +}
> +
> +static inline void lidt(const struct desc_ptr *idtr)
> +{
> +    asm volatile ("lidt %0" :: "m" (*idtr));
> +}
> +
> +static inline void lldt(unsigned int sel)
> +{
> +    asm volatile ("lldt %w0" :: "rm" (sel));
> +}
> +
> +static inline void ltr(unsigned int sel)
> +{
> +    asm volatile ("ltr %w0" :: "rm" (sel));
> +}

As can be seen from the code you replace in ldt.h, in headers we
generally prefer to use __asm__ (and __volatile__ where needed).
I'm sure this isn't consistent, so I won't insist. However, style-wise
please add blanks immediately inside the parentheses. With at least
this last point taken care of
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan


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