[PATCH] powernv/eeh: Fix oops when probing cxl devices

[Michael Ellerman]

On Wed, 2019-10-16 at 16:28:33 UTC, Frederic Barrat wrote:
> Recent cleanup in the way EEH support is added to a device causes a
> kernel oops when the cxl driver probes a device and creates virtual
> devices discovered on the FPGA:
> 
>     BUG: Kernel NULL pointer dereference at 0x000000a0
>     Faulting instruction address: 0xc000000000048070
>     Oops: Kernel access of bad area, sig: 7 [#1]
>     ...
>     NIP [c000000000048070] eeh_add_device_late.part.9+0x50/0x1e0
>     LR [c00000000004805c] eeh_add_device_late.part.9+0x3c/0x1e0
>     Call Trace:
>     [c000200e43983900] [c00000000079e250] _dev_info+0x5c/0x6c (unreliable)
>     [c000200e43983980] [c0000000000d1ad0] pnv_pcibios_bus_add_device+0x60/0xb0
>     [c000200e439839f0] [c0000000000606d0] pcibios_bus_add_device+0x40/0x60
>     [c000200e43983a10] [c0000000006aa3a0] pci_bus_add_device+0x30/0x100
>     [c000200e43983a80] [c0000000006aa4d4] pci_bus_add_devices+0x64/0xd0
>     [c000200e43983ac0] [c00800001c429118] cxl_pci_vphb_add+0xe0/0x130 [cxl]
>     [c000200e43983b00] [c00800001c4242ac] cxl_probe+0x504/0x5b0 [cxl]
>     [c000200e43983bb0] [c0000000006bba1c] local_pci_probe+0x6c/0x110
>     [c000200e43983c30] [c000000000159278] work_for_cpu_fn+0x38/0x60
> 
> The root cause is that those cxl virtual devices don't have a
> representation in the device tree and therefore no associated pci_dn
> structure. In eeh_add_device_late(), pdn is NULL, so edev is NULL and
> we oops.
> 
> We never had explicit support for EEH for those virtual
> devices. Instead, EEH events are reported to the (real) pci device and
> handled by the cxl driver. Which can then forward to the virtual
> devices and handle dependencies. The fact that we try adding EEH
> support for the virtual devices is new and a side-effect of the recent
> cleanup.
> 
> This patch fixes it by skipping adding EEH support on powernv for
> devices which don't have a pci_dn structure.
> 
> The cxl driver doesn't create virtual devices on pseries so this patch
> doesn't fix it there intentionally.
> 
> Fixes: b905f8cdca77 ("powerpc/eeh: EEH for pSeries hot plug")
> Signed-off-by: Frederic Barrat <fbarrat at linux.ibm.com>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/a8a30219ba78b1abb92091102b632f8e9bbdbf03

cheers