Re: [Xen-devel] [RFC PATCH v2 3/8] arm/mem_access: Add defines supporting PTs with varying page sizes

[Julien Grall <julien.grall@xxxxxxx>]

Hi Sergej,

On 06/01/2017 04:18 PM, Sergej Proskurin wrote:
> The ARMv8 architecture supports pages with different (4K, 16K, and 64K) sizes.
> To enable guest page table walks for various configurations, this commit
> extends the defines and helpers of the current implementation.
>
> Signed-off-by: Sergej Proskurin <proskurin@xxxxxxxxxxxxx>
> ---
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Cc: Julien Grall <julien.grall@xxxxxxx>
> ---
>   xen/include/asm-arm/page.h | 67 ++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 67 insertions(+)
>
> diff --git a/xen/include/asm-arm/page.h b/xen/include/asm-arm/page.h
> index 4b46e8831c..6222b1d4a2 100644
> --- a/xen/include/asm-arm/page.h
> +++ b/xen/include/asm-arm/page.h
> @@ -500,6 +500,73 @@ static inline int gva_to_ipa(vaddr_t va, paddr_t *paddr, 
> unsigned int flags)
>   
>   #define PAGE_ALIGN(x) (((x) + PAGE_SIZE - 1) & PAGE_MASK)
>   
> +#define LPAE_SHIFT_4K           (9)
> +#define LPAE_SHIFT_16K          (11)
> +#define LPAE_SHIFT_64K          (13)
> +
> +#define LPAE_ENTRIES_4K         (_AC(1,U) << LPAE_SHIFT_4K)
> +#define LPAE_ENTRIES_16K        (_AC(1,U) << LPAE_SHIFT_16K)
> +#define LPAE_ENTRIES_64K        (_AC(1,U) << LPAE_SHIFT_64K)
It sounds like to me you can introduce macros to avoid all the 
redundancies as you did below for GUEST_TABLE_OFFSET.
This macro would take a granularity in parameter and create all the 
*_gran define associated to it.
But I am not fully convinced they all need to be defined. You only use 
them once and could easily use LPAE_SHIFT_*K to get what you need in the 
guest page table walker.
Cheers,

--
Julien Grall

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