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Message-ID: <20250715180407.47426-4-Smita.KoralahalliChannabasappa@amd.com>
Date: Tue, 15 Jul 2025 18:04:03 +0000
From: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
To: <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<nvdimm@...ts.linux.dev>, <linux-fsdevel@...r.kernel.org>,
<linux-pm@...r.kernel.org>
CC: 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>, Dan Williams
<dan.j.williams@...el.com>, Matthew Wilcox <willy@...radead.org>, Jan Kara
<jack@...e.cz>, "Rafael J . Wysocki" <rafael@...nel.org>, Len Brown
<len.brown@...el.com>, Pavel Machek <pavel@...nel.org>, Li Ming
<ming.li@...omail.com>, Jeff Johnson <jeff.johnson@....qualcomm.com>, "Ying
Huang" <huang.ying.caritas@...il.com>, Yao Xingtao <yaoxt.fnst@...itsu.com>,
Peter Zijlstra <peterz@...radead.org>, Greg KH <gregkh@...uxfoundation.org>,
Nathan Fontenot <nathan.fontenot@....com>, Smita Koralahalli
<Smita.KoralahalliChannabasappa@....com>, Terry Bowman
<terry.bowman@....com>, Robert Richter <rrichter@....com>, Benjamin Cheatham
<benjamin.cheatham@....com>, PradeepVineshReddy Kodamati
<PradeepVineshReddy.Kodamati@....com>, Zhijian Li <lizhijian@...itsu.com>
Subject: [PATCH v5 3/7] cxl/acpi: Add background worker to coordinate with cxl_mem probe completion
Introduce a background worker in cxl_acpi to delay SOFT RESERVE handling
until the cxl_mem driver has probed at least one device. This coordination
ensures that DAX registration or fallback handling for soft-reserved
regions is not triggered prematurely.
The worker waits on cxl_wait_queue, which is signaled via
cxl_mem_active_inc() during cxl_mem_probe(). Once at least one memory
device probe is confirmed, the worker invokes wait_for_device_probe()
to allow the rest of the CXL device hierarchy to complete initialization.
Additionally, it also handles initialization order issues where
cxl_acpi_probe() may complete before other drivers such as cxl_port or
cxl_mem have loaded, especially when cxl_acpi and cxl_port are built-in
and cxl_mem is a loadable module. In such cases, using only
wait_for_device_probe() is insufficient, as it may return before all
relevant probes are registered.
While region creation happens in cxl_port_probe(), waiting on
cxl_mem_active() would be sufficient as cxl_mem_probe() can only succeed
after the port hierarchy is in place. Furthermore, since cxl_mem depends
on cxl_pci, this also guarantees that cxl_pci has loaded by the time the
wait completes.
As cxl_mem_active() infrastructure already exists for tracking probe
activity, cxl_acpi can use it without introducing new coordination
mechanisms.
Co-developed-by: Nathan Fontenot <Nathan.Fontenot@....com>
Signed-off-by: Nathan Fontenot <Nathan.Fontenot@....com>
Co-developed-by: Terry Bowman <terry.bowman@....com>
Signed-off-by: Terry Bowman <terry.bowman@....com>
Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
---
drivers/cxl/acpi.c | 18 ++++++++++++++++++
drivers/cxl/core/probe_state.c | 5 +++++
drivers/cxl/cxl.h | 2 ++
3 files changed, 25 insertions(+)
diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
index ca06d5acdf8f..3a27289e669b 100644
--- a/drivers/cxl/acpi.c
+++ b/drivers/cxl/acpi.c
@@ -823,6 +823,20 @@ static int pair_cxl_resource(struct device *dev, void *data)
return 0;
}
+static void cxl_softreserv_mem_work_fn(struct work_struct *work)
+{
+ if (!wait_event_timeout(cxl_wait_queue, cxl_mem_active(), 30 * HZ))
+ pr_debug("Timeout waiting for cxl_mem probing");
+
+ wait_for_device_probe();
+}
+static DECLARE_WORK(cxl_sr_work, cxl_softreserv_mem_work_fn);
+
+static void cxl_softreserv_mem_update(void)
+{
+ schedule_work(&cxl_sr_work);
+}
+
static int cxl_acpi_probe(struct platform_device *pdev)
{
int rc = 0;
@@ -903,6 +917,9 @@ static int cxl_acpi_probe(struct platform_device *pdev)
cxl_bus_rescan();
out:
+ /* Update SOFT RESERVE resources that intersect with CXL regions */
+ cxl_softreserv_mem_update();
+
return rc;
}
@@ -934,6 +951,7 @@ static int __init cxl_acpi_init(void)
static void __exit cxl_acpi_exit(void)
{
+ cancel_work_sync(&cxl_sr_work);
platform_driver_unregister(&cxl_acpi_driver);
cxl_bus_drain();
}
diff --git a/drivers/cxl/core/probe_state.c b/drivers/cxl/core/probe_state.c
index 5ba4b4de0e33..3089b2698b32 100644
--- a/drivers/cxl/core/probe_state.c
+++ b/drivers/cxl/core/probe_state.c
@@ -2,9 +2,12 @@
/* Copyright(c) 2022 Intel Corporation. All rights reserved. */
#include <linux/atomic.h>
#include <linux/export.h>
+#include <linux/wait.h>
#include "cxlmem.h"
static atomic_t mem_active;
+DECLARE_WAIT_QUEUE_HEAD(cxl_wait_queue);
+EXPORT_SYMBOL_NS_GPL(cxl_wait_queue, "CXL");
bool cxl_mem_active(void)
{
@@ -13,10 +16,12 @@ bool cxl_mem_active(void)
return false;
}
+EXPORT_SYMBOL_NS_GPL(cxl_mem_active, "CXL");
void cxl_mem_active_inc(void)
{
atomic_inc(&mem_active);
+ wake_up(&cxl_wait_queue);
}
EXPORT_SYMBOL_NS_GPL(cxl_mem_active_inc, "CXL");
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 3f1695c96abc..3117136f0208 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -903,6 +903,8 @@ void cxl_coordinates_combine(struct access_coordinate *out,
bool cxl_endpoint_decoder_reset_detected(struct cxl_port *port);
+extern wait_queue_head_t cxl_wait_queue;
+
/*
* Unit test builds overrides this to __weak, find the 'strong' version
* of these symbols in tools/testing/cxl/.
--
2.17.1
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