Re: [PATCH 2/3] ArmPkg/UncachedMemoryAllocationLib: use CWG value to align pool allocations

[Leif Lindholm <leif.lindholm@linaro.org>]

On Tue, Feb 28, 2017 at 12:13:11PM +0000, Ard Biesheuvel wrote:
> Uncached pool allocations are aligned to the data cache line length under
> the assumption that this is sufficient to prevent cache maintenance from
> corrupting adjacent allocations. However, the value to use in such cases
> is architecturally called the Cache Writeback Granule (CWG), which is
> essentially the maximum Dcache line length rather than the minimum.
> 
> Note that this is mostly a cosmetical fix, given that the pool allocation
> is turned into a page allocation later, and rounded up accordingly.
> 
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

> ---
>  ArmPkg/Library/UncachedMemoryAllocationLib/UncachedMemoryAllocationLib.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/ArmPkg/Library/UncachedMemoryAllocationLib/UncachedMemoryAllocationLib.c b/ArmPkg/Library/UncachedMemoryAllocationLib/UncachedMemoryAllocationLib.c
> index cd13a7da92e0..0d8abad23433 100644
> --- a/ArmPkg/Library/UncachedMemoryAllocationLib/UncachedMemoryAllocationLib.c
> +++ b/ArmPkg/Library/UncachedMemoryAllocationLib/UncachedMemoryAllocationLib.c
> @@ -545,7 +545,7 @@ UncachedInternalAllocatePool (
>    IN UINTN            AllocationSize
>    )
>  {
> -  UINTN CacheLineLength = ArmDataCacheLineLength ();
> +  UINTN CacheLineLength = ArmCacheWritebackGranule ();
>    return UncachedInternalAllocateAlignedPool (MemoryType, AllocationSize, CacheLineLength);
>  }
>  
> -- 
> 2.7.4
>