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powerpc64/kexec: Hard disable ftrace before switching to the new kernel 

If function_graph tracer is enabled during kexec, we see the below
exception in the simulator:
	root@(none):/# kexec -e
	kvm: exiting hardware virtualization
	kexec_core: Starting new kernel
	[   19.262020070,5] OPAL: Switch to big-endian OS
	kexec: Starting switchover sequence.
	Interrupt to 0xC000000000004380 from 0xC000000000004380
	** Execution stopped: Continuous Interrupt, Instruction caused exception,  **

Now that we have a more effective way to completely disable ftrace on
ppc64, let's also use that before switching to a new kernel during
kexec.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Naveen N. Rao 2018-04-19 12:34:06 +05:30 committed by Michael Ellerman
parent a4bc64d305
commit 88b1a8547f
1 changed files with 2 additions and 0 deletions
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2
arch/powerpc/kernel/machine_kexec.c
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@ -98,12 +98,14 @@ void machine_kexec(struct kimage *image)
int save_ftrace_enabled;
save_ftrace_enabled = __ftrace_enabled_save();
this_cpu_disable_ftrace();
if (ppc_md.machine_kexec)
ppc_md.machine_kexec(image);
else
default_machine_kexec(image);
this_cpu_enable_ftrace();
__ftrace_enabled_restore(save_ftrace_enabled);
/* Fall back to normal restart if we're still alive. */