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>

diff --git a/arch/powerpc/kernel/machine_kexec.c b/arch/powerpc/kernel/machine_kexec.c
index 2694d078741d08c9f32a05c7ea6323867ddde63d..936c7e2d421e7b5fa6eab58b20d4fbc7fd7d5fd7 100644 (file)
--- a/arch/powerpc/kernel/machine_kexec.c
+++ b/arch/powerpc/kernel/machine_kexec.c
@@ -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. */