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Recently we merged the native xive support for Power9, and then separately some reworks for doorbell IPI support. In isolation both series were OK, but the merged result had a bug in one case. On P9 DD1 we use pnv_p9_dd1_cause_ipi() which tries to use doorbells, and then falls back to the interrupt controller. However the fallback is implemented by calling icp_ops->cause_ipi. But now that xive support is merged we might be using xive, in which case icp_ops is not initialised, it's a xics specific structure. This leads to an oops such as: Unable to handle kernel paging request for data at address 0x00000028 Oops: Kernel access of bad area, sig: 11 [#1] NIP pnv_p9_dd1_cause_ipi+0x74/0xe0 LR smp_muxed_ipi_message_pass+0x54/0x70 To fix it, rather than using icp_ops which might be NULL, have both xics and xive set smp_ops->cause_ipi, and then in the powernv code we save that as ic_cause_ipi before overriding smp_ops->cause_ipi. For paranoia add a WARN_ON() to check if somehow smp_ops->cause_ipi is NULL. Fixes: b866cc2199d6 ("powerpc: Change the doorbell IPI calling convention") Tested-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.