[Intel-wired-lan] [PATCH net-next] igb: assume MSI-X interrupts during initialization

[Don Buchholz]

On 09/17/15 05:46, Stefan Assmann wrote:
> In igb_sw_init() the sequence of calls was changed from
> igb_init_queue_configuration()
> igb_init_interrupt_scheme()
> igb_probe_vfs()
> to
> igb_probe_vfs()
> igb_init_queue_configuration()
> igb_init_interrupt_scheme()
>
> This results in adapter->flags not having the IGB_FLAG_HAS_MSIX bit set
> during igb_probe_vfs()->igb_enable_sriov(). Therefore SR-IOV does not
> get enabled properly and we run into a NULL pointer if the max_vfs
> module parameter is specified (adapter->vf_data does not get allocated,
> crash on accessing the structure).
>
> [    7.419348] BUG: unable to handle kernel NULL pointer dereference at 0000000000000048
> [    7.419367] IP: [<ffffffffa02161c6>] igb_reset+0xe6/0x5d0 [igb]
> [    7.419370] PGD 0
> [    7.419373] Oops: 0002 [#1] SMP
> [    7.419381] Modules linked in: ahci(+) libahci igb(+) i40e(+) vxlan ip6_udp_tunnel udp_tunnel megaraid_sas(+) ixgbe(+) mdio
> [    7.419385] CPU: 0 PID: 4 Comm: kworker/0:0 Not tainted 4.2.0+ #153
> [    7.419387] Hardware name: Dell Inc. PowerEdge R720/0C4Y3R, BIOS 1.6.0 03/07/2013
> [...]
> [    7.419431] Call Trace:
> [    7.419442]  [<ffffffffa0217236>] igb_probe+0x8b6/0x1340 [igb]
> [    7.419447]  [<ffffffff814c7f15>] local_pci_probe+0x45/0xa0
>
> Prevent this by setting the IGB_FLAG_HAS_MSIX bit before calling
> igb_probe_vfs(). The real interrupt capabilities will be checked during
> igb_init_interrupt_scheme() so this is safe to do.
>
> Signed-off-by: Stefan Assmann <sassmann at kpanic.de>
> ---
>   drivers/net/ethernet/intel/igb/igb_main.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
> index e174fbb..ba019fc 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -2986,6 +2986,9 @@ static int igb_sw_init(struct igb_adapter *adapter)
>          }
>   #endif /* CONFIG_PCI_IOV */
>
> +       /* Assume MSI-X interrupts, will be checked during IRQ allocation */
> +       adapter->flags |= IGB_FLAG_HAS_MSIX;
> +
>          igb_probe_vfs(adapter);
>
>          igb_init_queue_configuration(adapter);
> --
> 2.4.3
>
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>


Tested-by: Don Buchholz <donald.buchholz at intel.com>

Verfied - patch fixes problem.

First, issue was re-created with unpatched kernel. On test system, the 
file /etc/modprobe.d/igb.conf contains "options igb max_vfs=4 debug=16". 
The unpatched kernel behaved poorly in two manners: (1) During system 
boot, 'igb' driver would load with no panic or stack trace, but no VFs 
were created. (2) When the module was removed (rmmod igb) and then 
reloaded (modprobe igb) the "null pointer dereference / Oops" occurs and 
stack trace is generated.

Applied patch and verified 'igb' now loads as expected (VFs are created 
at boot time and no "Oops" occurs.)