Commit 14d4ae5c authored Apr 05, 2017 by Benjamin Herrenschmidt Committed by Michael Ellerman Apr 06, 2017

powerpc: Add optional smp_ops->prepare_cpu SMP callback



Some platforms (will) need to perform allocations before bringing
a new CPU online. Doing it from smp_ops->setup_cpu is the wrong
thing to do:

 - It has no useful failure path (too late)
 - Calling any allocator will enable interrupts prematurely
   causing problems with large decrementer among others

Instead, add a new callback that is called from __cpu_up (so from
the context trying to online the new CPU) at a point where we
can safely allocate and handle failures.

This will be used by XIVE support.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

parent 22bd64a6

arch/powerpc/include/asm/smp.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -44,6 +44,7 @@ struct smp_ops_t {
		#endif
		void (*probe)(void);
		int (*kick_cpu)(int nr);
		int (*prepare_cpu)(int nr);
		void (*setup_cpu)(int nr);
		void (*bringup_done)(void);
		void (*take_timebase)(void);

arch/powerpc/kernel/smp.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -521,6 +521,16 @@ int __cpu_up(unsigned int cpu, struct task_struct *tidle)

		cpu_idle_thread_init(cpu, tidle);

		/*
		* The platform might need to allocate resources prior to bringing
		* up the CPU
		*/
		if (smp_ops->prepare_cpu) {
		rc = smp_ops->prepare_cpu(cpu);
		if (rc)
		return rc;
		}

		/* Make sure callin-map entry is 0 (can be leftover a CPU
		* hotplug
		*/