Re: [PATCH v3 3/6] powerpc/kexec: Disable ftrace before switching to the new kernel
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2018-03-26 22:31:01
"Naveen N. Rao" [off-list ref] writes:
quoted hunk ↗ jump to hunk
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 disable ftrace, let's use that before switching to a new kernel during kexec. Signed-off-by: Naveen N. Rao <redacted> --- arch/powerpc/kernel/machine_kexec.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)diff --git a/arch/powerpc/kernel/machine_kexec.c b/arch/powerpc/kernel/machine_kexec.c index 2694d078741d..4a1b24a9dd61 100644 --- a/arch/powerpc/kernel/machine_kexec.c +++ b/arch/powerpc/kernel/machine_kexec.c@@ -95,16 +95,14 @@ void arch_crash_save_vmcoreinfo(void) */ void machine_kexec(struct kimage *image) { - int save_ftrace_enabled; - - save_ftrace_enabled = __ftrace_enabled_save(); + get_paca()->ftrace_disabled = 1;
This doesn't compile on 32-bit: Failed: powerpc-next/corenet32_smp_defconfig/powerpc-5.3 (http://kisskb.ozlabs.ibm.com/kisskb/buildresult/13314085/log/) /kisskb/src/arch/powerpc/kernel/machine_kexec.c:105:12: error: invalid type argument of '->' (have 'int') /kisskb/src/arch/powerpc/kernel/machine_kexec.c:98:12: error: invalid type argument of '->' (have 'int') /kisskb/src/arch/powerpc/kernel/machine_kexec.c:98:2: error: implicit declaration of function 'get_paca' [-Werror=implicit-function-declaration] A wrapper is probably best that does nothing on 32-bit. cheers