linux-kernel - [PATCH 4.2.y-ckt 096/206] Revert "powerpc/eeh: Fix crash in eeh_add_device

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Message-Id: <1465507015-23052-97-git-send-email-kamal@canonical.com>
Date:	Thu,  9 Jun 2016 14:15:05 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	"Guilherme G . Piccoli" <gpiccoli@...ux.vnet.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 096/206] Revert "powerpc/eeh: Fix crash in eeh_add_device_early() on Cell"

4.2.8-ckt12 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: "Guilherme G. Piccoli" <gpiccoli@...ux.vnet.ibm.com>

commit c2078d9ef600bdbe568c89e5ddc2c6f15b7982c8 upstream.

This reverts commit 89a51df5ab1d38b257300b8ac940bbac3bb0eb9b.

The function eeh_add_device_early() is used to perform EEH
initialization in devices added later on the system, like in
hotplug/DLPAR scenarios. Since the commit 89a51df5ab1d ("powerpc/eeh:
Fix crash in eeh_add_device_early() on Cell") a new check was introduced
in this function - Cell has no EEH capabilities which led to kernel oops
if hotplug was performed, so checking for eeh_enabled() was introduced
to avoid the issue.

However, in architectures that EEH is present like pSeries or PowerNV,
we might reach a case in which no PCI devices are present on boot time
and so EEH is not initialized. Then, if a device is added via DLPAR for
example, eeh_add_device_early() fails because eeh_enabled() is false,
and EEH end up not being enabled at all.

This reverts the aforementioned patch since a new verification was
introduced by the commit d91dafc02f42 ("powerpc/eeh: Delay probing EEH
device during hotplug") and so the original Cell issue does not happen
anymore.

Reviewed-by: Gavin Shan <gwshan@...ux.vnet.ibm.com>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@...ux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 arch/powerpc/kernel/eeh.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/eeh.c b/arch/powerpc/kernel/eeh.c
index 01c961d..1109964 100644
--- a/arch/powerpc/kernel/eeh.c
+++ b/arch/powerpc/kernel/eeh.c
@@ -1071,7 +1071,7 @@ void eeh_add_device_early(struct pci_dn *pdn)
 	struct pci_controller *phb;
 	struct eeh_dev *edev = pdn_to_eeh_dev(pdn);

-	if (!edev || !eeh_enabled())
+	if (!edev)
 		return;

 	if (!eeh_has_flag(EEH_PROBE_MODE_DEVTREE))
-- 
2.7.4