[PATCH v3 1/2] pci/hotplug/pnv_php: Fix hotplug driver crash on Powernv

[Shawn Anastasio]

Hi Krishna,

On 6/24/24 7:09 AM, Krishna Kumar wrote:
> Description of the problem: The hotplug driver for powerpc
> (pci/hotplug/pnv_php.c) gives kernel crash when we try to
> hot-unplug/disable the PCIe switch/bridge from the PHB.
> 
> Root Cause of Crash: The crash is due to the reason that, though the msi
> data structure has been released during disable/hot-unplug path and it
> has been assigned with NULL, still during unregistartion the code was
> again trying to explicitly disable the msi which causes the Null pointer
> dereference and kernel crash.
> 
> Proposed Fix : The fix is to correct the check during unregistration path
> so that the code should not  try to invoke pci_disable_msi/msix() if its
> data structure is already freed.
> 
> Cc: Michael Ellerman <mpe at ellerman.id.au>
> Cc: Nicholas Piggin <npiggin at gmail.com>
> Cc: Christophe Leroy <christophe.leroy at csgroup.eu>
> Cc: "Aneesh Kumar K.V" <aneesh.kumar at kernel.org>
> Cc: Bjorn Helgaas <bhelgaas at google.com>
> Cc: Gaurav Batra <gbatra at linux.ibm.com>
> Cc: Nathan Lynch <nathanl at linux.ibm.com>
> Cc: Brian King <brking at linux.vnet.ibm.com>
> 
> Signed-off-by: Krishna Kumar <krishnak at linux.ibm.com>

As with v1, I can confirm that this patch solves the panic encountered
when hotplugging PCIe bridges on POWER9.

Tested-by: Shawn Anastasio <sanastasio at raptorengineering.com>

Thanks,
Shawn