Re: [PATCH v4 2/8] ARM: expand fixmap region to 3MB

[Will Deacon <will.deacon@arm.com>]

Hi Kees, Rob,

On Wed, Aug 13, 2014 at 06:06:27PM +0100, Kees Cook wrote:
> From: Rob Herring <robh@kernel.org>
> 
> With commit a05e54c103b0 ("ARM: 8031/2: change fixmap mapping region to
> support 32 CPUs"), the fixmap region was expanded to 2MB, but it
> precluded any other uses of the fixmap region. In order to support other
> uses the fixmap region needs to be expanded beyond 2MB. Fortunately, the
> adjacent 1MB range 0xffe00000-0xfff00000 is availabe.
> 
> Remove fixmap_page_table ptr and lookup the page table via the virtual
> address so that the fixmap region can span more that one pmd. The 2nd
> pmd is already created since it is shared with the vector page.

[...]

> diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
> index 45aeaaca9052..81061987ac45 100644
> --- a/arch/arm/mm/highmem.c
> +++ b/arch/arm/mm/highmem.c
> @@ -18,19 +18,20 @@
>  #include <asm/tlbflush.h>
>  #include "mm.h"
>  
> -pte_t *fixmap_page_table;
> -
>  static inline void set_fixmap_pte(int idx, pte_t pte)
>  {
>  	unsigned long vaddr = __fix_to_virt(idx);
> -	set_pte_ext(fixmap_page_table + idx, pte, 0);
> +	pte_t *ptep = pte_offset_kernel(pmd_off_k(vaddr), vaddr);
> +
> +	set_pte_ext(ptep, pte, 0);
>  	local_flush_tlb_kernel_page(vaddr);
>  }

Minor comment, but we can drop the ifx parameter here now, right? It looks a
bit weird having a setter/getter pair of functions where the type signatures
aren't the inverse.

Will