[PATCH] PCI/AER: Add a null check before eeh_ops->notify_resume callback.

[Bryant G. Ly]

On 2/22/18 5:58 AM, Vaibhav Jain wrote:

> This patch puts a NULL check before branching to the address pointed
> to by eeh_ops->notify_resume in eeh_report_resume(). The callback
> is used to notify the arch EEH code that a pci device is back
> online.
>
> For PPC64 presently, only an implementation for pseries platform is
> available and not for powernv. Hence without this patch EEH recovery
> on all non-virtualized hosts is causing a kernel panic when
> CONFIG_PCI_IOV is set. The panic is usually is of the form:
>
> EEH: Notify device driver to resume
> Unable to handle kernel paging request for instruction fetch
> Faulting instruction address: 0x00000000
> Oops: Kernel access of bad area, sig: 11 [#1]
> <snip>
> LR eeh_report_resume+0x218/0x220
> Call Trace:
>  eeh_report_resume+0x1f0/0x220 (unreliable)
>  eeh_pe_dev_traverse+0x98/0x170
>  eeh_handle_normal_event+0x3f4/0x650
>  eeh_handle_event+0x188/0x380
>  eeh_event_handler+0x208/0x210
>  kthread+0x168/0x1b0
>  ret_from_kernel_thread+0x5c/0xb4
>
> Cc: Bryant G. Ly <bryantly at linux.vnet.ibm.com>
> Fixes: 856e1eb9bdd4("PCI/AER: Add uevents in AER and EEH error/resume")
> Signed-off-by: Vaibhav Jain <vaibhav at linux.vnet.ibm.com>
> ---
>  arch/powerpc/kernel/eeh_driver.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kernel/eeh_driver.c b/arch/powerpc/kernel/eeh_driver.c
> index beea2182d754..932858a293ea 100644
> --- a/arch/powerpc/kernel/eeh_driver.c
> +++ b/arch/powerpc/kernel/eeh_driver.c
> @@ -384,7 +384,8 @@ static void *eeh_report_resume(void *data, void *userdata)
>  	eeh_pcid_put(dev);
>  	pci_uevent_ers(dev, PCI_ERS_RESULT_RECOVERED);
>  #ifdef CONFIG_PCI_IOV
> -	eeh_ops->notify_resume(eeh_dev_to_pdn(edev));
> +	if (eeh_ops->notify_resume)
> +		eeh_ops->notify_resume(eeh_dev_to_pdn(edev));
>  #endif
>  	return NULL;
>  }

A version of this patch already upstreamed. 

https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?h=fixes&id=521ca5a9859a870e354d1a6b84a6ff4c07bbceb0

-Bryant