[edk2-devel] [PATCH v1 1/2] MdePkg/BaseCacheMaintenanceLib: Enable RISCV CMO

[Sunil V L]

Hi Dhaval,

Thank you for looking at CMO support!

General comments first:
1) Please have a cover letter patch and move some part of the commit
message to cover letter. Please CC all maintainers in the cover letter
also.
2) Please run BaseTools/Scripts/GetMaintainer.py and CC all maintainers.
3) Follow
https://github.com/tianocore/tianocore.github.io/wiki/EDK-II-Development-Process

Have you run CI tests?

On Fri, Mar 24, 2023 at 09:13:41PM +0530, Dhaval Sharma wrote:
> Adding code to support Cache Management Operations
> (CMO) defined by RV spec https://github.com/riscv/riscv-CMOs
> Notes:
> 1. CMO only supports block based Operations. Meaning complete
> cache flush/invd/clean Operations are not available
> 2. Current implementation uses ifence instructions but it
> maybe platform specific. Many platforms may not support cache
> Operations based on ifence.
fence.i? 

IMO, it is better to add a new library such as BaseRiscV64CMOLib and
included conditionally in the DSC for the platforms which support CMO.
BaseCacheMaintenanceLib will continue to have default fence.i
implementation. Is there an issue with this?

> 3. For now adding CMO on top of ifence as it is not considered
> harmful.
> 4. This requires support for GCC12.2 onwards.
>
Yeah, this is another challenge like zifencei_zicsr which we could
workaround and support both older and newer tool chain. But for CMO, 
I don't see any option but to support only GCC12.2+.

Thanks,
Sunil


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