Re: [PATCH] x86/resctrl: Don't try to free nonexistent RMIDs

[Dave Martin <Dave.Martin@arm.com>]

Hi,

On Mon, Jun 17, 2024 at 08:53:38AM -0700, Reinette Chatre wrote:
> Hi Dave,
> 
> On 6/17/24 4:55 AM, Dave Martin wrote:
> > Hi Reinette,
> > 
> > On Fri, Jun 14, 2024 at 03:47:58PM -0700, Reinette Chatre wrote:
> > > Hi Dave,
> > > 
> > > On 6/14/24 9:08 AM, Dave Martin wrote:
> > > > Commit 6791e0ea3071 ("x86/resctrl: Access per-rmid structures by
> > > > index") adds logic to map individual monitoring groups into a
> > > > global index space used for tracking allocated RMIDs.
> > > > 
> > > > That patch keept the logic to ignore requests to free the default
> > > 
> > > keept -> kept
> > > 
> > > nitpick: I actually do not know if "that patch" gets same hate as
> > > "this patch" so to avoid any potential feedback about this I'd like
> > > to suggest that this is rewritten without this term. Perhaps
> > > something like: "Requests to free the default RMID in free_rmid()
> > > are ignored, and this works fine on x86."
> > > 
> > > > RMID in free_rmid(), and this works fine on x86.
> > > > 
> > 
> > How about recasting the first paragraph into the past tense (since it
> > relates a past commit), and rewording as "Requests to free the default
> > RMID continued to be ignored in free_rmid(), and this works fine on
> > x86."
> 
> Please keep it in the present tense. I do not see this as relating to
> a "past commit" but instead it is an existing commit responsible for
> current behavior. Documentation/process/maintainer-tip.rst contains
> some example changelogs created by x86 maintainers that captures their
> requirements. The beginning "context" portion is always in present
> tense.

Fair enough.  I'll reword this as per your suggestion.

[...]

> > > > Tested on x86 (But so far for the monitors-present case.
> > > 
> > > Tested by booting with "rdt=!cmt,!mbmtotal,!mbmlocal".
> > 
> > Thanks (I take it that's your test, not a request to be more specific
> > about mine?)
> 
> Yes, I did test it with those parameters. You are also welcome to
> add:
> Tested-by: Reinette Chatre <reinette.chatre@intel.com>

Ah, right.  Thanks.

> > As it happens I tested with rdt=cmt,mbmtotal,mbmlocal,l3cat,l3cdp
> > (though I made no effort to exercise these features other than running
> > the selftests).  I can note this in the commit if you prefer.
> 
> hmmm ... those parameters should not be necessary unless the system
> has those features forced off by default because of errata. Doing
> functional testing on these systems via such enabling is fine
> though.
> 
> Reinette

I got these kernel args from James.  Apparently some of these features
are defaulted to off by the firmware on the box I'm using, but we're not
sure why.  I haven't dug into it.

Cheers
---Dave