Re: [Minios-devel] [PATCH 00/47] MINI-OS: enable the arm64 support

[Julien Grall <julien.grall@xxxxxxx>]

Hi Shijie,

Few generic comments on this series.

On 03/14/2018 09:39 AM, Huang Shijie wrote:
>   2.) Tests
>     I tested this patch set on Softiron(arm64) and x86_64 platform.
How about arm32? What is the state after this series?

On the previous version, I clearly suggested 2 paths to add support for 
arm64:
"I can see two solutions going forward:
        1) The arm directory is first reshaped to welcome arm64. This 
means:
                * moving out arm32 specific code
                * switch to LPAE page-table
                * introducing helpers for common code to call 
arch-specific code
           On the code is reshaped, the arm64 series is added on top.

        2) Start the arm64 port from a clean slate and then port arm32 
over.
Knowing the state of the arm32 port, I would lean towards 2). This would 
allow more flexibility and make easier to review. At the moment, I have 
to hunt down the code to see what is missing."
This series does not follow any of them and end up to have #if 
defined(__aarch64__) in the common code. This really defeating the 
purpose of the refactoring below.
To be clear, I am not suggesting to add arm32 port, I am just asking to 
not make things worst than the current state.
>    4.) The comments from Julien which I did not follow:
>       0) Use p2m_set_entry to setup the page table.
>          I did not have good understanding of the p2m_set_entry().
>         So I use my familiar way to setup the page table.
I haven't seen any discussion from you since November about 
misunderstanding in my suggestions...
>       1) Move dsb/dmb/mb to common place.
>          I did not do so, because I found the older arm32 archs
>          use "mcr" to do the memory barriers.
Hu? B4.2.5 in ARM DDI  0406C.c says:

"In ARMv7, ARM deprecates any use of these CP15 c7 operations, and 
strongly recommends that software uses the ISB , DSB , and DMB 
instructions instead."
Mini-OS will always run on ARMv7 or later architecture.
        
Cheers,

--
Julien Grall

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