Messages in this thread Patch in this message | | | From | Chunyu Hu <> | Subject | [PATCH] x86/idt: load idt early in start_secondary | Date | Mon, 27 Nov 2017 22:21:39 +0800 |
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For ap, idt is first loaded in cpu_init() with load_current_idt(), that is to say, no exception can be handled before there. And then the idt_table has been completed by the bp.
While there are some WARNs which needs the UD exception handling in the early boot code might be triggered when something uexpected happens during boot. In that case, cpu would fail to boot as the exception can't be handled. A WARNing during boot is not usually meaning the system could not boot.
One use case is when ftrace=function is setup in kernel cmdline, the ftrace callback function will be called for every traced function. And in my case, the first traced function is load_ucode_ap. And there are WARN()s in function trace callback handling, it failed to reboot as one of the WARN()s is triggered before load_current_idt() executed.
To make WARN()s can work earlier to ap, we load the idt_table early in start_secondary, and keep the second time idt load in cpu_init, as there is a load_ucode_ap() there.
Signed-off-by: Chunyu Hu <chuhu@redhat.com> --- arch/x86/kernel/smpboot.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 3d01df7..05a97d5 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -237,7 +237,7 @@ static void notrace start_secondary(void *unused) load_cr3(swapper_pg_dir); __flush_tlb_all(); #endif - + load_current_idt(); cpu_init(); x86_cpuinit.early_percpu_clock_init(); preempt_disable(); -- 1.8.3.1
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