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| author | Nicholas Piggin <npiggin@gmail.com> | 2022-12-16 14:59:28 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-03-17 10:50:31 +0300 |
| commit | be2e726fa03af85d797d4d75bdac3c23e70ac36f (patch) | |
| tree | 1645ff1e149d886c59f2f60fac51ca987f1c3531 /arch/powerpc | |
| parent | 5b5fab270f4db7d19c8fcb057f3e22f5ee798617 (diff) | |
| download | linux-be2e726fa03af85d797d4d75bdac3c23e70ac36f.tar.xz | |
powerpc/64: Fix task_cpu in early boot when booting non-zero cpuid
[ Upstream commit 9fa24404f5044967753a6cd3e5e36f57686bec6e ]
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
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'arch/powerpc')
| -rw-r--r-- | arch/powerpc/kernel/setup_64.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c index a0dee7354fe6..a43865e0fb4b 100644 --- a/arch/powerpc/kernel/setup_64.c +++ b/arch/powerpc/kernel/setup_64.c @@ -396,6 +396,11 @@ void __init early_setup(unsigned long dt_ptr) } fixup_boot_paca(paca_ptrs[boot_cpuid]); setup_paca(paca_ptrs[boot_cpuid]); /* install the paca into registers */ + // smp_processor_id() now reports boot_cpuid + +#ifdef CONFIG_SMP + task_thread_info(current)->cpu = boot_cpuid; // fix task_cpu(current) +#endif /* * Configure exception handlers. This include setting up trampolines |