Patch "powerpc/eeh: Probe after unbalanced kref check" has been added to the 4.1-stable tree

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

powerpc/eeh: Probe after unbalanced kref check

to the 4.1-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:
powerpc-eeh-probe-after-unbalanced-kref-check.patch
and it can be found in the queue-4.1 subdirectory.

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

From: Daniel Axtens <[email protected]>
Date: Fri, 14 Aug 2015 16:03:19 +1000
Subject: powerpc/eeh: Probe after unbalanced kref check

From: Daniel Axtens <[email protected]>

commit e642d11bdbfe8eb10116ab3959a2b5d75efda832 upstream.

In the complete hotplug case, EEH PEs are supposed to be released and set to NULL. Normally, this is done by eeh_remove_device(), which is called from pcibios_release_device().

However, if something is holding a kref to the device, it will not be released, and the PE will remain. eeh_add_device_late() has a check for this which will explictly destroy the PE in this case.

This check in eeh_add_device_late() occurs after a call to eeh_ops->probe(). On PowerNV, probe is a pointer to pnv_eeh_probe(), which will exit without probing if there is an existing PE.

This means that on PowerNV, devices with outstanding krefs will not be rediscovered by EEH correctly after a complete hotplug. This is affecting CXL (CAPI) devices in the field.

Put the probe after the kref check so that the PE is destroyed and affected devices are correctly rediscovered by EEH.

---
 arch/powerpc/kernel/eeh.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

@@ -1118,9 +1118,6 @@ void eeh_add_device_late(struct pci_dev
 		return;
 	}
 
-	if (eeh_has_flag(EEH_PROBE_MODE_DEV))
-		eeh_ops->probe(pdn, NULL);
-
 	/*
 	 * The EEH cache might not be removed correctly because of
 	 * unbalanced kref to the device during unplug time, which

@@ -1144,6 +1141,9 @@ void eeh_add_device_late(struct pci_dev
 		dev->dev.archdata.edev = NULL;
 	}
 
+	if (eeh_has_flag(EEH_PROBE_MODE_DEV))
+		eeh_ops->probe(pdn, NULL);
+
 	edev->pdev = dev;
 	dev->dev.archdata.edev = edev;
 

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

queue-4.1/powerpc-eeh-probe-after-unbalanced-kref-check.patch queue-4.1/cxl-remove-racy-attempt-to-force-eeh-invocation-in-reset.patch queue-4.1/cxl-fix-unbalanced-pci_dev_get-in-cxl_probe.patch