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Message-ID: <20241106020931.165802-1-sashal@kernel.org>
Date: Tue, 5 Nov 2024 21:09:30 -0500
From: Sasha Levin <sashal@...nel.org>
To: stable@...r.kernel.org,
dan.j.williams@...el.com
Cc: Gregory Price <gourry@...rry.net>,
Davidlohr Bueso <dave@...olabs.net>,
Jonathan Cameron <jonathan.cameron@...wei.com>,
Dave Jiang <dave.jiang@...el.com>,
Alison Schofield <alison.schofield@...el.com>,
Vishal Verma <vishal.l.verma@...el.com>,
Ira Weiny <ira.weiny@...el.com>,
Jonathan Cameron <Jonathan.Cameron@...wei.com>,
Alejandro Lucero <alucerop@....com>,
linux-cxl@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: FAILED: Patch "cxl/port: Fix CXL port initialization order when the subsystem is built-in" failed to apply to v6.6-stable tree
The patch below does not apply to the v6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@...r.kernel.org>.
Thanks,
Sasha
------------------ original commit in Linus's tree ------------------
>From 6575b268157f37929948a8d1f3bafb3d7c055bc1 Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@...el.com>
Date: Fri, 25 Oct 2024 12:32:55 -0700
Subject: [PATCH] cxl/port: Fix CXL port initialization order when the
subsystem is built-in
When the CXL subsystem is built-in the module init order is determined
by Makefile order. That order violates expectations. The expectation is
that cxl_acpi and cxl_mem can race to attach. If cxl_acpi wins the race,
cxl_mem will find the enabled CXL root ports it needs. If cxl_acpi loses
the race it will retrigger cxl_mem to attach via cxl_bus_rescan(). That
flow only works if cxl_acpi can assume ports are enabled immediately
upon cxl_acpi_probe() return. That in turn can only happen in the
CONFIG_CXL_ACPI=y case if the cxl_port driver is registered before
cxl_acpi_probe() runs.
Fix up the order to prevent initialization failures. Ensure that
cxl_port is built-in when cxl_acpi is also built-in, arrange for
Makefile order to resolve the subsys_initcall() order of cxl_port and
cxl_acpi, and arrange for Makefile order to resolve the
device_initcall() (module_init()) order of the remaining objects.
As for what contributed to this not being found earlier, the CXL
regression environment, cxl_test, builds all CXL functionality as a
module to allow to symbol mocking and other dynamic reload tests. As a
result there is no regression coverage for the built-in case.
Reported-by: Gregory Price <gourry@...rry.net>
Closes: http://lore.kernel.org/20241004212504.1246-1-gourry@gourry.net
Tested-by: Gregory Price <gourry@...rry.net>
Fixes: 8dd2bc0f8e02 ("cxl/mem: Add the cxl_mem driver")
Cc: stable@...r.kernel.org
Cc: Davidlohr Bueso <dave@...olabs.net>
Cc: Jonathan Cameron <jonathan.cameron@...wei.com>
Cc: Dave Jiang <dave.jiang@...el.com>
Cc: Alison Schofield <alison.schofield@...el.com>
Cc: Vishal Verma <vishal.l.verma@...el.com>
Cc: Ira Weiny <ira.weiny@...el.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Reviewed-by: Ira Weiny <ira.weiny@...el.com>
Tested-by: Alejandro Lucero <alucerop@....com>
Reviewed-by: Alejandro Lucero <alucerop@....com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
Link: https://patch.msgid.link/172988474904.476062.7961350937442459266.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Ira Weiny <ira.weiny@...el.com>
---
drivers/cxl/Kconfig | 1 +
drivers/cxl/Makefile | 20 ++++++++++++++------
drivers/cxl/port.c | 17 ++++++++++++++++-
3 files changed, 31 insertions(+), 7 deletions(-)
diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig
index 29c192f20082c..876469e23f7a7 100644
--- a/drivers/cxl/Kconfig
+++ b/drivers/cxl/Kconfig
@@ -60,6 +60,7 @@ config CXL_ACPI
default CXL_BUS
select ACPI_TABLE_LIB
select ACPI_HMAT
+ select CXL_PORT
help
Enable support for host managed device memory (HDM) resources
published by a platform's ACPI CXL memory layout description. See
diff --git a/drivers/cxl/Makefile b/drivers/cxl/Makefile
index db321f48ba52e..2caa90fa4bf25 100644
--- a/drivers/cxl/Makefile
+++ b/drivers/cxl/Makefile
@@ -1,13 +1,21 @@
# SPDX-License-Identifier: GPL-2.0
+
+# Order is important here for the built-in case:
+# - 'core' first for fundamental init
+# - 'port' before platform root drivers like 'acpi' so that CXL-root ports
+# are immediately enabled
+# - 'mem' and 'pmem' before endpoint drivers so that memdevs are
+# immediately enabled
+# - 'pci' last, also mirrors the hardware enumeration hierarchy
obj-y += core/
-obj-$(CONFIG_CXL_PCI) += cxl_pci.o
-obj-$(CONFIG_CXL_MEM) += cxl_mem.o
+obj-$(CONFIG_CXL_PORT) += cxl_port.o
obj-$(CONFIG_CXL_ACPI) += cxl_acpi.o
obj-$(CONFIG_CXL_PMEM) += cxl_pmem.o
-obj-$(CONFIG_CXL_PORT) += cxl_port.o
+obj-$(CONFIG_CXL_MEM) += cxl_mem.o
+obj-$(CONFIG_CXL_PCI) += cxl_pci.o
-cxl_mem-y := mem.o
-cxl_pci-y := pci.o
+cxl_port-y := port.o
cxl_acpi-y := acpi.o
cxl_pmem-y := pmem.o security.o
-cxl_port-y := port.o
+cxl_mem-y := mem.o
+cxl_pci-y := pci.o
diff --git a/drivers/cxl/port.c b/drivers/cxl/port.c
index 861dde65768fe..9dc394295e1fc 100644
--- a/drivers/cxl/port.c
+++ b/drivers/cxl/port.c
@@ -208,7 +208,22 @@ static struct cxl_driver cxl_port_driver = {
},
};
-module_cxl_driver(cxl_port_driver);
+static int __init cxl_port_init(void)
+{
+ return cxl_driver_register(&cxl_port_driver);
+}
+/*
+ * Be ready to immediately enable ports emitted by the platform CXL root
+ * (e.g. cxl_acpi) when CONFIG_CXL_PORT=y.
+ */
+subsys_initcall(cxl_port_init);
+
+static void __exit cxl_port_exit(void)
+{
+ cxl_driver_unregister(&cxl_port_driver);
+}
+module_exit(cxl_port_exit);
+
MODULE_DESCRIPTION("CXL: Port enumeration and services");
MODULE_LICENSE("GPL v2");
MODULE_IMPORT_NS(CXL);
--
2.43.0
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