Re: [added to the 4.1 stable tree] powerpc/iommu: Remove the dependency on EEH struct in DDW mechanism

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On 06/03/2016 06:36 PM, Sasha Levin wrote:
From: "Guilherme G. Piccoli" <gpiccoli@xxxxxxxxxxxxxxxxxx>

This patch has been added to the 4.1 stable tree. If you have any
objections, please let us know.

===============

[ Upstream commit 8445a87f7092bc8336ea1305be9306f26b846d93 ]

Commit 39baadbf36ce ("powerpc/eeh: Remove eeh information from pci_dn")
changed the pci_dn struct by removing its EEH-related members.
As part of this clean-up, DDW mechanism was modified to read the device
configuration address from eeh_dev struct.

As a consequence, now if we disable EEH mechanism on kernel command-line
for example, the DDW mechanism will fail, generating a kernel oops by
dereferencing a NULL pointer (which turns to be the eeh_dev pointer).

This patch just changes the configuration address calculation on DDW
functions to a manual calculation based on pci_dn members instead of
using eeh_dev-based address.

No functional changes were made. This was tested on pSeries, both
in PHyp and qemu guest.

Fixes: 39baadbf36ce ("powerpc/eeh: Remove eeh information from pci_dn")
Cc: stable@xxxxxxxxxxxxxxx # v3.4+
Reviewed-by: Gavin Shan <gwshan@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>


Hi Sasha, thanks for letting me know.

Unfortunately, this patch has an issue; the proposed fix is simple and was already sent to linuxppc-dev list by Gavin Shan.

Link to the proposed fix (already tested): https://patchwork.ozlabs.org/patch/626492

Thanks, and sorry for the inconvenience.
Cheers,


Guilherme

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