linux-kernel - [PATCH v6 4/9] PCI: Add additional checks for flr reset

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Message-ID: <20251201220823.3350-5-alifm@linux.ibm.com>
Date: Mon,  1 Dec 2025 14:08:18 -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, Benjamin Block <bblock@...ux.ibm.com>
Subject: [PATCH v6 4/9] PCI: Add additional checks for flr reset

If a device is in an error state, then any reads of device registers can
return error value. Add addtional checks to validate if a device is in an
error state before doing an flr reset.

Cc: stable@...r.kernel.org
Reviewed-by: Benjamin Block <bblock@...ux.ibm.com>
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 28c6b9e7f526..0f3ca4ff27e8 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4503,12 +4503,19 @@ EXPORT_SYMBOL_GPL(pcie_flr);
  */
 int pcie_reset_flr(struct pci_dev *dev, bool probe)
 {
+	u32 reg;
+
 	if (dev->dev_flags & PCI_DEV_FLAGS_NO_FLR_RESET)
 		return -ENOTTY;
 
 	if (!(dev->devcap & PCI_EXP_DEVCAP_FLR))
 		return -ENOTTY;
 
+	if (pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, &reg)) {
+		pci_warn(dev, "Device unable to do an FLR\n");
+		return -ENOTTY;
+	}
+
 	if (probe)
 		return 0;
 
-- 
2.43.0