linux-kernel - [PATCH RFC 07/25] PCI/LUO: Save and restore driver name

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Message-Id: <20250728-luo-pci-v1-7-955b078dd653@kernel.org>
Date: Mon, 28 Jul 2025 01:24:37 -0700
From: Chris Li <chrisl@...nel.org>
To: Bjorn Helgaas <bhelgaas@...gle.com>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 "Rafael J. Wysocki" <rafael@...nel.org>, Danilo Krummrich <dakr@...nel.org>, 
 Len Brown <lenb@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org, 
 linux-acpi@...r.kernel.org, David Matlack <dmatlack@...gle.com>, 
 Pasha Tatashin <tatashin@...gle.com>, Jason Miu <jasonmiu@...gle.com>, 
 Vipin Sharma <vipinsh@...gle.com>, Saeed Mahameed <saeedm@...dia.com>, 
 Adithya Jayachandran <ajayachandra@...dia.com>, 
 Parav Pandit <parav@...dia.com>, William Tu <witu@...dia.com>, 
 Mike Rapoport <rppt@...nel.org>, Chris Li <chrisl@...nel.org>, 
 Jason Gunthorpe <jgg@...pe.ca>, Leon Romanovsky <leon@...nel.org>
Subject: [PATCH RFC 07/25] PCI/LUO: Save and restore driver name

Save the PCI driver name into "struct pci_dev_ser" during the PCI
prepare callback.

After kexec, use driver_set_override() to ensure the device is
bound only to the saved driver.

Clear the override after the finish callback.

Signed-off-by: Chris Li <chrisl@...nel.org>
---
 drivers/pci/liveupdate.c | 36 ++++++++++++++++++++++++++++++++++--
 drivers/pci/pci.h        |  2 ++
 drivers/pci/probe.c      |  2 ++
 3 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/liveupdate.c b/drivers/pci/liveupdate.c
index 6b85673f4ec20add7e49b04dc44f1bcd868adbdc..189827c6111b2c00ebb24404a205cde3f75d33c3 100644
--- a/drivers/pci/liveupdate.c
+++ b/drivers/pci/liveupdate.c
@@ -21,6 +21,7 @@ static LIST_HEAD(probe_devices);
 struct pci_dev_ser {
 	u32	path;		/* domain + bus + slot + fn */
 	u8	requested;
+	char	driver_name[63];
 	u64	driver_data;	/* driver data */
 };
 
@@ -91,6 +92,10 @@ static int build_liveupdate_devices(struct list_head *head)
 
 static void dev_cleanup_liveupdate(struct device *dev)
 {
+	struct pci_dev *pdev = to_pci_dev(dev);
+
+	if (liveupdate_state_updated())
+		WARN_ON(driver_set_override(dev, &pdev->driver_override, "", 0));
 	dev->lu.depended = 0;
 	dev->lu.dev_state = NULL;
 	list_del_init(&dev->lu.lu_next);
@@ -139,7 +144,13 @@ static int pci_get_device_path(struct pci_dev *pdev)
 static int pci_save_device_state(struct device *dev, struct pci_dev_ser *s)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
+	const char *name = dev->driver->name;
 
+	if (!name)
+		return -ENXIO;
+	if (strlen(name) > sizeof(s->driver_name) - 1)
+		return -ENOSPC;
+	strscpy(s->driver_name, name, sizeof(s->driver_name));
 	s->path = pci_get_device_path(pdev);
 	s->requested = dev->lu.requested;
 	return 0;
@@ -370,9 +381,9 @@ static void pci_dev_do_restore(struct pci_dev *dev, struct pci_dev_ser *s)
 		dev->dev.lu.requested = 1;
 	else
 		dev->dev.lu.depended = 1;
-	pci_info(dev, "liveupdate restore [%s] data: [%llx]\n",
+	pci_info(dev, "liveupdate restore [%s] driver: %s data: [%llx]\n",
 		 s->requested ? "requested" : "depended",
-		 s->driver_data);
+		 s->driver_name, s->driver_data);
 	list_move_tail(&dev->dev.lu.lu_next, &probe_devices);
 }
 
@@ -392,6 +403,27 @@ void pci_liveupdate_restore(struct pci_dev *dev)
 			return pci_dev_do_restore(dev, s);
 }
 
+void pci_liveupdate_override_driver(struct pci_dev *dev)
+{
+	struct pci_dev_ser *s = dev->dev.lu.dev_state;
+	int ret;
+	int len;
+
+	if (!s)
+		return;
+
+	len = strlen(s->driver_name);
+	if (!len)
+		return;
+
+	ret = driver_set_override(&dev->dev,
+				  &dev->driver_override,
+				  s->driver_name, len);
+	if (ret)
+		panic("PCI Liveupdate override driver failed: %s", s->driver_name);
+}
+
+
 static int __init pci_liveupdate_init(void)
 {
 	int ret;
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index c9a7383753949994e031dc362920286a475fe2ab..b79a18c5e948980fe2ef3f0a10e0d795b1eee6d7 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -1161,8 +1161,10 @@ static inline int pci_msix_write_tph_tag(struct pci_dev *pdev, unsigned int inde
 
 #ifdef CONFIG_LIVEUPDATE
 void pci_liveupdate_restore(struct pci_dev *dev);
+void pci_liveupdate_override_driver(struct pci_dev *dev);
 #else
 static inline void pci_liveupdate_restore(struct pci_dev *dev) {}
+static inline void pci_liveupdate_override_driver(struct pci_dev *dev) {}
 #endif
 
 #endif /* DRIVERS_PCI_H */
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index a0605af1a699cd07b09897172803dcba1d2da9f9..e41a1bef2083aa9184fd1c894d5de964f19d5c01 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2714,6 +2714,8 @@ void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
 	/* Set up MSI IRQ domain */
 	pci_set_msi_domain(dev);
 
+	pci_liveupdate_override_driver(dev);
+
 	/* Notifier could use PCI capabilities */
 	ret = device_add(&dev->dev);
 	WARN_ON(ret < 0);

-- 
2.50.1.487.gc89ff58d15-goog