Re: [XEN v1] xen/Arm: Remove the extra assignment

[Julien Grall <julien@xxxxxxx>]

Hi Ayan,

Title: It suggests that this is modifying arch/arm whereas you are 
updating the Arm part of the ns16550 driver.
In addition to that, from a reader PoV, it is more important to emphase 
on the fact the truncation check is removed rather than the extra 
assignment.
So I would suggest the following title:

xen/ns16550: Remove unneeded truncation check in the DT init code

On 01/12/2022 17:31, Ayan Kumar Halder wrote:
> As "io_size" and "uart->io_size" are both u64, so there will be no truncation.
> Thus, one can remove the ASSERT() and extra assignment.
>
> In an earlier commit (7c1de0038895cbc75ebd0caffc5b0f3f03c5ad51),
Please use 12-digit hash and provide the commit title.

> "ns16550.io_size" was u32 and "io_size" was u64. Thus, the ASSERT() was needed
> to check if the values are the same.
> However, in a later commit (c9f8e0aee507bec25104ca5535fde38efae6c6bc),
Ditto.

> "ns16550.io_size" was changed to u64. Thus, the ASSERT() became redundant.
Those two paragraphs explaining your reasoning why the truncation check 
is removed. So I think they should be moved first. Then you can add the 
initial paragraph to explain the resolution.
However... I wonder whether it would not be better to switch 'io_size' 
to paddr_t because, as you said earlier one, on 32-bit ARMv8-R the 
address is 32-bit. Therefore:
 1. it sounds pointless to store the size using 64-bit
 2. the truncation check still make sense (maybe hardened) in the 
32-bit ARMv8-R to catch buggy DT.
Cheers,

--
Julien Grall