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

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Message-ID: <87msn5llkv.fsf@mail.lhotse>
Date: Fri, 28 Jun 2024 14:48:00 +1000
From: Michael Ellerman <mpe@...erman.id.au>
To: Shawn Anastasio <sanastasio@...torengineering.com>, Krishna Kumar
 <krishnak@...ux.ibm.com>, npiggin@...il.com
Cc: nathanl@...ux.ibm.com, aneesh.kumar@...nel.org,
 linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
 christophe.leroy@...roup.eu, gbatra@...ux.ibm.com, bhelgaas@...gle.com,
 tpearson@...torengineering.com, oohall@...il.com,
 brking@...ux.vnet.ibm.com, mahesh.salgaonkar@...ibm.com,
 linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v3 1/2] pci/hotplug/pnv_php: Fix hotplug driver crash on
 Powernv

Shawn Anastasio <sanastasio@...torengineering.com> writes:
> 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@...erman.id.au>
>> Cc: Nicholas Piggin <npiggin@...il.com>
>> Cc: Christophe Leroy <christophe.leroy@...roup.eu>
>> Cc: "Aneesh Kumar K.V" <aneesh.kumar@...nel.org>
>> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
>> Cc: Gaurav Batra <gbatra@...ux.ibm.com>
>> Cc: Nathan Lynch <nathanl@...ux.ibm.com>
>> Cc: Brian King <brking@...ux.vnet.ibm.com>
>> 
>> Signed-off-by: Krishna Kumar <krishnak@...ux.ibm.com>
>
> As with v1, I can confirm that this patch solves the panic encountered
> when hotplugging PCIe bridges on POWER9.

Was the panic reported anywhere? So we can link to the report in the
commit.

cheers