Re: [XEN v8 2/5] xen/arm: Introduce choice to enable 64/32 bit physical addressing

[Julien Grall <julien@xxxxxxx>]

Hi Ayan,

On 02/06/2023 13:07, Ayan Kumar Halder wrote:
> Some Arm based hardware platforms which does not support LPAE
> (eg Cortex-R52), uses 32 bit physical addresses.
> Also, users may choose to use 32 bits to represent physical addresses
> for optimization.
>
> To support the above use cases, we have introduced arch independent
> config to choose if the physical address can be represented using
> 32 bits (PHYS_ADDR_T_32) or 64 bits (!PHYS_ADDR_T_32).
> For now only ARM_32 provides support to enable 32 bit physical
> addressing.
>
> When PHYS_ADDR_T_32 is defined, PADDR_BITS is set to 32. Note that we
> use "unsigned long" (not "uint32_t") to denote the datatype of physical
> address. This is done to avoid using a cast each time PAGE_* macros are
> used on paddr_t. For eg PAGE_SIZE is defined as unsigned long. Thus,
> each time PAGE_SIZE is used with paddr_t, the result will be
> "unsigned long".
> On 32-bit architecture, "unsigned long" is 32-bit wide. Thus, it can be
> used to denote physical address.
>
> When PHYS_ADDR_T_32 is not defined for ARM_32, PADDR_BITS is set to 40.
> For ARM_64, PADDR_BITS is set to 48.
> The last two are same as the current configuration used today on Xen.
>
> Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
> Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
Acked-by: Julien Grall <jgrall@xxxxxxxxxx>

Cheers,

--
Julien Grall