Thread (10 messages) 10 messages, 2 authors, 2018-03-27

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
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