linux-kernel - [PATCH] ACPI/MRRM: Fix default max memory region

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Message-ID: <20250523172001.1761634-1-anil.s.keshavamurthy@intel.com>
Date: Fri, 23 May 2025 13:20:01 -0400
From: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
To: tony.luck@...el.com,
	rafael@...nel.org
Cc: anil.s.keshavamurthy@...el.com,
	yu.c.chen@...el.com,
	lenb@...nel.org,
	linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	patches@...ts.linux.dev
Subject: [PATCH] ACPI/MRRM: Fix default max memory region

Per the spec, the default max memory region must be 1 covering
all system memory.

When platform does not provide ACPI MRRM table or
when CONFIG_ACPI is opted out, the acpi_mrrm_max_mem_region() function
defaults to  returning 1 region complying to RDT spec.

Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
---
 drivers/acpi/acpi_mrrm.c | 3 ++-
 include/linux/acpi.h     | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/acpi_mrrm.c b/drivers/acpi/acpi_mrrm.c
index 2f22f013959a..26c1a4e6b6ec 100644
--- a/drivers/acpi/acpi_mrrm.c
+++ b/drivers/acpi/acpi_mrrm.c
@@ -14,7 +14,8 @@
 #include <linux/string.h>
 #include <linux/sysfs.h>
 
-static int max_mem_region = -ENOENT;
+/* Default assume one memory region covering all system memory, per the spec */
+static int max_mem_region = 1;
 
 /* Access for use by resctrl file system */
 int acpi_mrrm_max_mem_region(void)
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index e72100c0684f..f102c0fe3431 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1101,7 +1101,7 @@ static inline acpi_handle acpi_get_processor_handle(int cpu)
 
 static inline int acpi_mrrm_max_mem_region(void)
 {
-	return -ENOENT;
+	return 1;
 }
 
 #endif	/* !CONFIG_ACPI */
-- 
2.47.1