Re: [PATCH v7 04/10] x86,fs/resctrl: Implement "io_alloc" enable/disable handlers

[Reinette Chatre]

Hi Babu,

On 7/10/25 10:16 AM, Babu Moger wrote:
> "io_alloc" enables direct insertion of data from I/O devices into the
> cache.
> 
> On AMD systems, "io_alloc" feature is backed by L3 Smart Data Cache
> Injection Allocation Enforcement (SDCIAE). Change SDCIAE state by setting
> (to enable) or clearing (to disable) bit 1 of MSR L3_QOS_EXT_CFG on all
> logical processors within the cache domain.
> 
> Introduce architecture-specific call to enable and disable the feature.
> 
> The SDCIAE feature details are available in APM listed below [1].
> [1] AMD64 Architecture Programmer's Manual Volume 2: System Programming
> Publication # 24593 Revision 3.41 section 19.4.7 L3 Smart Data Cache
> Injection Allocation Enforcement (SDCIAE)
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
> Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> ---

...

>  
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 885026468440..c165ac333336 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c

The code looks good to me but rdtgroup.c is becoming bloated by being the default place for
any resctrl changes. While I do know there are counter examples (and I admit I do
not have a clear understanding of original intent) ctrlmondata.c is documented and supported
by its content as the place for cache allocation code. Could you please move these changes
to arch/x86/kernel/cpu/resctrl/ctrlmondata.c? I will try to highlight the other places where
I believe the either fs/resctrl/ctrlmondata.c or arch/x86/kernel/cpu/resctrl/ctrlmondata.c is
more appropriate but please as a high level consider where appropriate to move the IO alloc
code to be with the rest of the cache allocation code. Looking at the series it will help keep
a couple of existing static functions static and keep data structures local to cache allocation
code.

Reinette