linux-kernel - Re: [PATCH v13 11/27] x86/resctrl: Implement resctrl_arch_config

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Message-ID: <aDDjs4PZxeouNJr0@agluck-desk3>
Date: Fri, 23 May 2025 14:08:03 -0700
From: "Luck, Tony" <tony.luck@...el.com>
To: "Chatre, Reinette" <reinette.chatre@...el.com>,
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Subject: Re: [PATCH v13 11/27] x86/resctrl: Implement
 resctrl_arch_config_cntr() to assign a counter with ABMC

On Thu, May 22, 2025 at 10:16:16PM +0000, Luck, Tony wrote:
> > It looks to me as though there are a couple of changes in the telemetry work
> > that would benefit this work. https://lore.kernel.org/lkml/20250521225049.132551-2-tony.luck@intel.com/
> > switches the monitor events to be maintained in an array indexed by event ID, eliminating the
> > need for searching the evt_list that this work does in a couple of places. Also note the handy
> > new for_each_mbm_event() helper (https://lore.kernel.org/lkml/20250521225049.132551-5-tony.luck@intel.com/).
> 
> Yesterday I ran through the exercise of rebasing my AET patches on top of these
> ABMC patches in order to check whether the ABMC patches painted resctrl
> into some corner that would be hard to get back out of.
> 
> Good news: they don't.
> 
> There was a bunch of manual patching to make the first four patches fit on top
> of the ABMC code, but I also noticed a few places where things were simpler
> after combining the two series.
> 
> Maybe a good path forward would be to take those first four patches from
> my AET series and then build ABMC on top of those.

As an encouragement to try this direction, I took my four patches
on top of tip x86/cache and then applied Babu's ABMC series.

Changes to Babu's code:
1) Adapt where needed for removal of evt_list. Use event array instead.
2) Use for_each_mbm_event() [Maybe didn't get all places?]
3) Bring the s/evt_val/evt_cfg/ fix into patch 20 from 21
4) Fix fir tree declaration for resctrl_process_assign()

I don't have an AMD system to check if the ABMC parts still work. But
it does pass the resctrl self tests, so legacy isn't broken.

Patches in the "my_mbm_plus_babu_abmc" branch of my kernel.org
repo: git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux.git

-Tony