Re: [Xen-devel] [PATCH v2 02/10] xen: arm: Add zeroeth level page table macros and defines

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2013-08-08 at 11:09 +0100, Tim Deegan wrote:
> At 14:31 +0100 on 07 Aug (1375885891), Ian Campbell wrote:
> > --- a/xen/include/asm-arm/page.h
> > +++ b/xen/include/asm-arm/page.h
> > @@ -337,7 +337,15 @@ static inline int gva_to_ipa(vaddr_t va, paddr_t 
> > *paddr)
> >  #define second_table_offset(va) TABLE_OFFSET(second_linear_offset(va))
> >  #define third_table_offset(va)  TABLE_OFFSET(third_linear_offset(va))
> >  
> > -#define clear_page(page)memset((void *)(page), 0, PAGE_SIZE)
> > +#ifdef CONFIG_ARM_64
> > +#define ZEROETH_SHIFT  (FIRST_SHIFT + LPAE_SHIFT)
> > +#define ZEROETH_SIZE   (1u << ZEROETH_SHIFT)
> > +#define ZEROETH_MASK   (~(ZEROETH_SIZE - 1))
> > +#define zeroeth_linear_offset(va) ((va) >> ZEROETH_SHIFT)
> > +#define zeroeth_table_offset(va)  TABLE_OFFSET(zeroeth_linear_offset(va))
> > +#endif
> 
> I'd prefer to see these defined alongside the other levels.  There's no
> harm in defining them on 32-bit builds.

My worry was that they would get used on 32-bit code paths by mistake,
which is a build error with this version but a (possibly obscure)
runtime error with the alternative.

> Also, please update the comment above LPAE_SHIFT to describe the 4-level 
> alternative. 

Will do.



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