Patch "PCI/PME: Handle invalid data when reading Root Status" has been added to the 3.18-stable tree

This is a note to let you know that I've just added the patch titled

PCI/PME: Handle invalid data when reading Root Status

to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
pci-pme-handle-invalid-data-when-reading-root-status.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Qiang <[email protected]>
Date: Thu, 28 Sep 2017 11:54:34 +0800
Subject: PCI/PME: Handle invalid data when reading Root Status

From: Qiang <[email protected]>

[ Upstream commit 3ad3f8ce50914288731a3018b27ee44ab803e170 ]

PCIe PME and native hotplug share the same interrupt number, so hotplug interrupts are also processed by PME. In some cases, e.g., a Link Down interrupt, a device may be present but unreachable, so when we try to read its Root Status register, the read fails and we get all ones data (0xffffffff).

Previously, we interpreted that data as PCI_EXP_RTSTA_PME being set, i.e., "some device has asserted PME," so we scheduled pcie_pme_work_fn(). This caused an infinite loop because pcie_pme_work_fn() tried to handle PME requests until PCI_EXP_RTSTA_PME is cleared, but with the link down, PCI_EXP_RTSTA_PME can't be cleared.

Check for the invalid 0xffffffff data everywhere we read the Root Status register.

1469d17dd341 ("PCI: pciehp: Handle invalid data when reading from non-existent devices") added similar checks in the hotplug driver.

[bhelgaas: changelog, also check in pcie_pme_work_fn(), use "~0" to follow other similar checks]

---
 drivers/pci/pcie/pme.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

@@ -233,6 +233,9 @@ static void pcie_pme_work_fn(struct work
 			break;
 
 		pcie_capability_read_dword(port, PCI_EXP_RTSTA, &rtsta);
+		if (rtsta == (u32) ~0)
+			break;
+
 		if (rtsta & PCI_EXP_RTSTA_PME) {
 			/*
 			 * Clear PME status of the port.  If there are other

@@ -280,7 +283,7 @@ static irqreturn_t pcie_pme_irq(int irq,
 	spin_lock_irqsave(&data->lock, flags);
 	pcie_capability_read_dword(port, PCI_EXP_RTSTA, &rtsta);
 
-	if (!(rtsta & PCI_EXP_RTSTA_PME)) {
+	if (rtsta == (u32) ~0 || !(rtsta & PCI_EXP_RTSTA_PME)) {
 		spin_unlock_irqrestore(&data->lock, flags);
 		return IRQ_NONE;
 	}

Patches currently in stable-queue which might be from [email protected] are

queue-3.18/pci-pme-handle-invalid-data-when-reading-root-status.patch