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System Reset, being an NMI, must return more carefully than other interrupts. It has traditionally returned via the nromal return from exception path, but that has a number of problems. - r13 does not get restored if returning to kernel. This is for interrupts which may cause a context switch, which sreset will never do. Interrupting OPAL (which uses a different r13) is one place where this causes breakage. - It may cause several other problems returning to kernel with preempt or TIF_EMULATE_STACK_STORE if it hits at the wrong time. It's safer just to have a simple restore and return, like machine check which is the other NMI. Signed-off-by: Nicholas Piggin <npiggin@gmail.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.