linux-kernel - [PATCH RFC 13/25] PCI/LUO: Check the device function numbers in restoration

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Message-Id: <20250728-luo-pci-v1-13-955b078dd653@kernel.org>
Date: Mon, 28 Jul 2025 01:24:43 -0700
From: 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 13/25] PCI/LUO: Check the device function numbers in
 restoration

From: Jason Miu <jasonmiu@...gle.com>

After liveupdate reboot, the device BDF shouldn't be changed from the
previous kernel. If this happens, the saved LUO device state cannot be
used, and panic the kernel.

Signed-off-by: Chris Li <chrisl@...nel.org>
---
 drivers/pci/liveupdate.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/pci/liveupdate.c b/drivers/pci/liveupdate.c
index 6b1c14d70fd16b0919ca22faae788069f3743708..ec2d7917441ceb4e3d7cd8becae41ca215cba7c3 100644
--- a/drivers/pci/liveupdate.c
+++ b/drivers/pci/liveupdate.c
@@ -393,6 +393,15 @@ static void pci_dev_do_restore(struct pci_dev *dev, struct pci_dev_ser *s)
 	pci_info(dev, "liveupdate restore [%s] driver: %s data: [%llx] num_vfs: %d\n",
 		 s->requested ? "requested" : "depended",
 		 s->driver_name, s->driver_data, s->num_vfs);
+
+	/*
+	 * The devfn got changed since reboot. We cannot restore device
+	 * info preserved by liveupdate
+	 */
+	if (s->devfn != dev->devfn)
+		panic("%s: Device and function numbers are changed from 0x%40x to 0x%40x\n",
+		      __func__, s->devfn, dev->devfn);
+
 	list_move_tail(&dev->dev.lu.lu_next, &probe_devices);
 }

-- 
2.50.1.487.gc89ff58d15-goog