linux-kernel - Re: [PATCH 5/6] cxl: add CXL_REGION_SYSRAM_DEFAULT

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Message-ID: <aWV-zstlCWPLT8g_@gourry-fedora-PF4VCD3F>
Date: Mon, 12 Jan 2026 18:07:58 -0500
From: Gregory Price <gourry@...rry.net>
To: "Cheatham, Benjamin" <benjamin.cheatham@....com>
Cc: linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-team@...a.com, dave@...olabs.net,
	jonathan.cameron@...wei.com, dave.jiang@...el.com,
	alison.schofield@...el.com, vishal.l.verma@...el.com,
	ira.weiny@...el.com, dan.j.williams@...el.com
Subject: Re: [PATCH 5/6] cxl: add CXL_REGION_SYSRAM_DEFAULT_* build options

On Mon, Jan 12, 2026 at 03:11:00PM -0600, Cheatham, Benjamin wrote:
> On 1/12/2026 10:35 AM, Gregory Price wrote:
> > DEFAULT_OFFLINE: Blocks will be offline after being created.
> > DEFAULT_ONLINE:  Blocks will be onlined in ZONE_MOVABLE
> > DEFAULT_ONLINE_NORMAL: Blocks will be onliend in ZONE_NORMAL.
> > 
> > This prevents users from having to use the MHP auto-online build config,
> > which may cause misbehaviors with other devices hotplugging memory.
> 
> Isn't the MHP auto-online build config still used in some flows? A quick note on
> when that option will still be used would be nice.

It's definitely still in use, and in fact we use it to manage many
systems with BIOS configured decoders.

That option super-cedes this option, which... is probably problematic,
and David might want to chime in on whether improving the hotplug+online
pattern to include the intended zone should dictate its removal.

~Gregory

> > +static int cxl_sysram_offline_memory(struct range *range)
> > +{
> > +	int offline_rc = 0;
> > +	int rc;
> > +
> > +	rc = walk_memory_blocks(range->start, range_len(range),
> > +				&offline_rc, offline_memory_block_cb);
> > +	if (!rc)
> > +		rc = offline_rc;
> > +
> > +	return rc;
> > +}
> 
> I think these two helpers can get moved into patch 2/6 when the 'store' attribute was defined. I don't
> see anything that requires they're in this patch and it would help reduce churn.
> 

Yeah this'll get reworked with the interface rework.

Thanks again,
Gregory