linux-kernel - [PATCH v6 3/9] PCI: Avoid saving config space state if inaccessible

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Message-ID: <20251201220823.3350-4-alifm@linux.ibm.com>
Date: Mon,  1 Dec 2025 14:08:17 -0800
From: Farhan Ali <alifm@...ux.ibm.com>
To: linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org
Cc: helgaas@...nel.org, lukas@...ner.de, alex@...zbot.org, clg@...hat.com,
        stable@...r.kernel.org, alifm@...ux.ibm.com, schnelle@...ux.ibm.com,
        mjrosato@...ux.ibm.com
Subject: [PATCH v6 3/9] PCI: Avoid saving config space state if inaccessible

The current reset process saves the device's config space state before
reset and restores it afterward. However, errors may occur unexpectedly,
and the device may become inaccessible or the config space itself may
be corrupted. This results in saving corrupted values that get
written back to the device during state restoration.

With a reset we want to recover/restore the device into a functional
state. So avoid saving the state of the config space when the
device config space is inaccessible/corrupted.

Signed-off-by: Farhan Ali <alifm@...ux.ibm.com>
---
 drivers/pci/pci.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 608d64900fee..28c6b9e7f526 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5105,6 +5105,7 @@ EXPORT_SYMBOL_GPL(pci_dev_unlock);
 
 static void pci_dev_save_and_disable(struct pci_dev *dev)
 {
+	u32 val;
 	const struct pci_error_handlers *err_handler =
 			dev->driver ? dev->driver->err_handler : NULL;
 
@@ -5125,6 +5126,12 @@ static void pci_dev_save_and_disable(struct pci_dev *dev)
 	 */
 	pci_set_power_state(dev, PCI_D0);
 
+	pci_read_config_dword(dev, PCI_COMMAND, &val);
+	if (PCI_POSSIBLE_ERROR(val)) {
+		pci_warn(dev, "Device config space inaccessible\n");
+		return;
+	}
+
 	pci_save_state(dev);
 	/*
 	 * Disable the device by clearing the Command register, except for
-- 
2.43.0