From: Nicholas Piggin npiggin@gmail.com

mainline inclusion from mainline-v6.3-rc1 commit 9fa24404f5044967753a6cd3e5e36f57686bec6e category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IAZSKU

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

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powerpc/64 can boot on a non-zero SMP processor id. Initially, the boot CPU is said to be "assumed to be 0" until early_init_devtree() discovers the id from the device tree. That is not a good description because the assumption can be wrong and that has to be handled, the better description is that 0 is used as a placeholder, and things are fixed after the real id is discovered.

smp_processor_id() is set to the boot cpuid, but task_cpu(current) is not, which causes the smp_processor_id() == task_cpu(current) invariant to be broken until init_idle() in sched_init().

This is quite fragile and could lead to subtle bugs in future. One bug is that validate_sp_size uses task_cpu() to get the process stack, so any stack trace from the booting CPU between early_init_devtree() and sched_init() will have problems. Early on paca_ptrs[0] will be poisoned, so that can cause machine checks dereferencing that memory in real mode. Later, validating the current stack pointer against the idle task of a different secondary will probably cause no stack trace to be printed.

Fix this by setting thread_info->cpu right after smp_processor_id() is set to the boot cpuid.

Signed-off-by: Nicholas Piggin npiggin@gmail.com [mpe: Fix SMP=n build as reported by sfr] Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20221216115930.2667772-3-npiggin@gmail.com Conflicts: arch/powerpc/kernel/setup_64.c [some funcs're added/deleted before/after modification] Signed-off-by: Bowen You youbowen2@huawei.com --- arch/powerpc/kernel/setup_64.c | 5 +++++ 1 file changed, 5 insertions(+)

diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c index 4875e84eb975..866b481f1166 100644 --- a/arch/powerpc/kernel/setup_64.c +++ b/arch/powerpc/kernel/setup_64.c @@ -325,6 +325,11 @@ void __init early_setup(unsigned long dt_ptr) initialise_paca(&boot_paca, 0); setup_paca(&boot_paca); fixup_boot_paca(); + // smp_processor_id() now reports boot_cpuid + +#ifdef CONFIG_SMP + task_thread_info(current)->cpu = boot_cpuid; // fix task_cpu(current) +#endif

/* -------- printk is now safe to use ------- */