linux-kernel - Re: [PATCH v3 3/3] acpi,srat: give memory block size advice based on CFMWS alignment

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Message-ID: <ZyDhLLCNXFN_M8l2@PC2K9PVX.TheFacebook.com>
Date: Tue, 29 Oct 2024 09:20:44 -0400
From: Gregory Price <gourry@...rry.net>
To: David Hildenbrand <david@...hat.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org, linux-mm@...ck.org, linux-cxl@...ck.org,
	Jonathan.Cameron@...wei.com, dan.j.williams@...el.com,
	rrichter@....com, Terry.Bowman@....com, dave.jiang@...el.com,
	ira.weiny@...el.com, alison.schofield@...el.com,
	dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
	tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
	rafael@...nel.org, lenb@...nel.org, osalvador@...e.de,
	gregkh@...uxfoundation.org, akpm@...ux-foundation.org,
	rppt@...nel.org
Subject: Re: [PATCH v3 3/3] acpi,srat: give memory block size advice based on
 CFMWS alignment

On Tue, Oct 29, 2024 at 01:42:12PM +0100, David Hildenbrand wrote:
> 
> >   static int __init acpi_parse_cfmws(union acpi_subtable_headers *header,
> >   				   void *arg, const unsigned long table_end)
> >   {
> > @@ -545,6 +569,15 @@ int __init acpi_numa_init(void)
> >   	 * Initialize a fake_pxm as the first available PXM to emulate.
> >   	 */
> > +	/* Align memblock size to CFMW regions if possible */
> > +	acpi_table_parse_cedt(ACPI_CEDT_TYPE_CFMWS, acpi_align_cfmws, NULL);
> > +
> > +	/*
> > +	 * Nodes start populating with blocks after this, so probe the max
> > +	 * block size to prevent it from changing in the future.
> > +	 */
> > +	memory_block_probe_max_size();
> > +
> 
> This looks odd. Why shouldn't we allow someone else to suggest/advise an
> even smaller "max size" ? I'd drop that.
> 

Ah, my reading of the numa_add_memblk path was mistaken.  I thought the
hotplug blocks would start being created immediately after this in the
acpi_parse_cfmws path - but memblk != memory_block x_x.

Will drop along with other recommended updates and submit v4.

~Gregory