Re: [RFC PATCH 1/7] MdePkg/Base: introduce MAX_ALLOC_ADDRESS

[Laszlo Ersek <lersek@redhat.com>]

On 12/07/18 12:22, Ard Biesheuvel wrote:
> On some architectures, the maximum representable address deviates from
> the virtual address range that is accessible by the firmware at boot
> time. For instance, on AArch64, UEFI mandates a 4 KB page size, which
> limits the address space to 48 bits, while more than that may be
> populated on a particular platform, for use by the OS.
> 
> So introduce a new macro MAX_ALLOC_ADDRESS, which represent the maximum
> address the firmware should take into account when allocating memory
> ranges that need to be accessible by the CPU at boot time. Initially,
> it just defaults to MAX_ADDRESS, but later on, architectures may elect
> to override it to a smaller number.
> 
> This means that all replacements of MAX_ADDRESS with MAX_ALLOC_ADDRESS
> are functional no-ops unless an architecture sets a value for the latter.
> 
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  MdePkg/Include/Base.h | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/MdePkg/Include/Base.h b/MdePkg/Include/Base.h
> index bc877d8125a5..618f8ea85ce7 100644
> --- a/MdePkg/Include/Base.h
> +++ b/MdePkg/Include/Base.h
> @@ -404,6 +404,10 @@ struct _LIST_ENTRY {
>  #define MIN_INT32  (((INT32) -2147483647) - 1)
>  #define MIN_INT64  (((INT64) -9223372036854775807LL) - 1)
>  
> +#ifndef MAX_ALLOC_ADDRESS
> +#define MAX_ALLOC_ADDRESS   MAX_ADDRESS
> +#endif
> +
>  #define  BIT0     0x00000001
>  #define  BIT1     0x00000002
>  #define  BIT2     0x00000004
> 

Given that the page size is dictated by the spec, I think adding
MAX_ALLOC_ADDRESS as a macro, and doing it here, is appropriate.

Reviewed-by: Laszlo Ersek <lersek@redhat.com>