Re: [XEN v7 08/11] xen/arm: Introduce choice to enable 64/32 bit physical addressing

[Michal Orzel <michal.orzel@xxxxxxx>]

Hi Ayan,

On 18/05/2023 16:39, 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. On 32-bit architecture, "unsigned long" is 32-bit
> wide. Thus, it can be used to denote physical address.
I think the only issue is when printing but you do not mention it as the root 
cause.
Also, FWIR it all comes down to PAGE_SIZE being defined as L.

I leave it up to you to decide if this is sufficient explanation.

Small notice:
Generally each commit in a series should build successfully. This is not the 
case starting from this patch
if user (or randconfig) selects 32-bit PA. But I know that other patches depend 
on PHYS_ADDR_T_32 so
I guess it would be difficult.

> 
> 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>

~Michal