Re: [PATCH v5 00/13] Arm cache coloring

[Michal Orzel <michal.orzel@xxxxxxx>]

Hi,

On 02/01/2024 10:51, Carlo Nonato wrote:
> 
> 
> Shared caches in multi-core CPU architectures represent a problem for
> predictability of memory access latency. This jeopardizes applicability
> of many Arm platform in real-time critical and mixed-criticality
> scenarios. We introduce support for cache partitioning with page
> coloring, a transparent software technique that enables isolation
> between domains and Xen, and thus avoids cache interference.
> 
> When creating a domain, a simple syntax (e.g. `0-3` or `4-11`) allows
> the user to define assignments of cache partitions ids, called colors,
> where assigning different colors guarantees no mutual eviction on cache
> will ever happen. This instructs the Xen memory allocator to provide
> the i-th color assignee only with pages that maps to color i, i.e. that
> are indexed in the i-th cache partition.
> 
> The proposed implementation supports the dom0less feature.
> The proposed implementation doesn't support the static-mem feature.
> The solution has been tested in several scenarios, including Xilinx Zynq
> MPSoCs.
> 
> In this patch series there are two major unacceptable workarounds for which
> I want to ask you for comments:
>  - #3: allocate_memory() has been moved in dom0less_build.c, so I just copied
>  it back to make it compile.
I would move it to domain_build.c and add a prototype in domain_build.h.
You could guard it together with allocate_bank_memory() for DOM0LESS || LLC or 
just
remove the guards (in former case, you would need to protect your call with 
#ifdef in construct_dom0()).

>  - #13: consider_modules() has been moved to arm32 only. Again I just copied 
> it.
I would move it to setup.c and add a prototype in setup.h.
As for the guards, if we want them (personally I don't see the need), you would 
need LLC || (ARM_32 && MMU).

BTW. Patchew reports some build issues in your series:
https://gitlab.com/xen-project/patchew/xen/-/pipelines/1124313980

Make sure to build test your series on different arches. You can ask on IRC to 
become a member
on gitlab so that you can trigger the pipeline by pushing the changes to your 
fork on people/<you>/xen.

~Michal