linux-kernel - [PATCH v2 2/2] ACPI: NUMA: Apply SRAT proximity domain to entire CFMWS window

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Date:   Tue, 13 Jun 2023 21:35:25 -0700
From:   alison.schofield@...el.com
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Mike Rapoport <rppt@...nel.org>
Cc:     Alison Schofield <alison.schofield@...el.com>, x86@...nel.org,
        linux-cxl@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Derick Marks <derick.w.marks@...el.com>
Subject: [PATCH v2 2/2] ACPI: NUMA: Apply SRAT proximity domain to entire CFMWS window

From: Alison Schofield <alison.schofield@...el.com>

Commit fd49f99c1809 ("ACPI: NUMA: Add a node and memblk for each
CFMWS not in SRAT") did not account for the case where the BIOS
only partially describes a CFMWS Window in the SRAT. That means
the omitted address ranges, of a partially described CFMWS Window,
do not get assigned to a NUMA node.

Replace the call to phys_to_target_node() with numa_add_memblks().
Numa_add_memblks() searches an HPA range for existing memblk(s)
and extends those memblk(s) to fill the entire CFMWS Window.

Extending the existing memblks is a simple strategy that reuses
SRAT defined proximity domains from part of a window to fill out
the entire window, based on the knowledge* that all of a CFMWS
window is of a similar performance class.

*Note that this heuristic will evolve when CFMWS Windows present
a wider range of characteristics. The extension of the proximity
domain, implemented here, is likely a step in developing a more
sophisticated performance profile in the future.

There is no change in behavior when the SRAT does not describe
the CFMWS Window at all. In that case, a new NUMA node with a
single memblk covering the entire CFMWS Window is created.

Fixes: fd49f99c1809 ("ACPI: NUMA: Add a node and memblk for each CFMWS not in SRAT")
Reported-by: Derick Marks <derick.w.marks@...el.com>
Suggested-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Alison Schofield <alison.schofield@...el.com>
Tested-by: Derick Marks <derick.w.marks@...el.com>
---
 drivers/acpi/numa/srat.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/acpi/numa/srat.c b/drivers/acpi/numa/srat.c
index 1f4fc5f8a819..12f330b0eac0 100644
--- a/drivers/acpi/numa/srat.c
+++ b/drivers/acpi/numa/srat.c
@@ -310,11 +310,16 @@ static int __init acpi_parse_cfmws(union acpi_subtable_headers *header,
 	start = cfmws->base_hpa;
 	end = cfmws->base_hpa + cfmws->window_size;

-	/* Skip if the SRAT already described the NUMA details for this HPA */
-	node = phys_to_target_node(start);
-	if (node != NUMA_NO_NODE)
+	/*
+	 * The SRAT may have already described NUMA details for all,
+	 * or a portion of, this CFMWS HPA range. Extend the memblks
+	 * found for any portion of the window to cover the entire
+	 * window.
+	 */
+	if (!numa_fill_memblks(start, end))
 		return 0;

+	/* No SRAT description. Create a new node. */
 	node = acpi_map_pxm_to_node(*fake_pxm);

 	if (node == NUMA_NO_NODE) {
-- 
2.37.3