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The 'resume_as_sreset' attribute of a cpu is set when a thread is entering a stop state on ppc books. It causes the thread to be re-routed to vector 0x100 when woken up by an exception. So it must be cleared on reset or a thread might be re-routed unexpectedly after a reset, when it was not in a stop state and/or when the appropriate exception handler isn't set up yet. Using skiboot, it can be tested by resetting the system when it is quiet and most threads are idle and in stop state. After the reset occurs, skiboot elects a primary thread and all the others wait in secondary_wait. The primary thread does all the system initialization from main_cpu_entry() and at some point, the decrementer interrupt starts ticking. The exception vector for the decrementer interrupt is in place, so that shouldn't be a problem. However, if that primary thread was in stop state prior to the reset, and because the resume_as_sreset parameters is still set, it is re-routed to exception vector 0x100. Which, at that time, is still defined as the entry point for BML. So that primary thread restarts as new and ends up being treated like any other secondary thread. All threads are now waiting in secondary_wait. It results in a full system hang with no message on the console, as the uart hasn't been init'ed yet. It's actually not obvious to realise what's happening if not tracing reset (-d cpu_reset). The fix is simply to clear the 'resume_as_sreset' attribute on reset. Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com> Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com> Reviewed-by: Cédric Le Goater <clg@kaod.org> Message-Id: <20220617095222.612212-1-fbarrat@linux.ibm.com> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com> |
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| .. | ||
| translate | ||
| arch_dump.c | ||
| compat.c | ||
| cpu_init.c | ||
| cpu-models.c | ||
| cpu-models.h | ||
| cpu-param.h | ||
| cpu-qom.h | ||
| cpu.c | ||
| cpu.h | ||
| dfp_helper.c | ||
| excp_helper.c | ||
| fpu_helper.c | ||
| gdbstub.c | ||
| helper_regs.c | ||
| helper_regs.h | ||
| helper.h | ||
| insn32.decode | ||
| insn64.decode | ||
| int_helper.c | ||
| internal.h | ||
| Kconfig | ||
| kvm_ppc.h | ||
| kvm-stub.c | ||
| kvm.c | ||
| machine.c | ||
| mem_helper.c | ||
| meson.build | ||
| misc_helper.c | ||
| mmu_common.c | ||
| mmu_helper.c | ||
| mmu-book3s-v3.c | ||
| mmu-book3s-v3.h | ||
| mmu-books.h | ||
| mmu-hash32.c | ||
| mmu-hash32.h | ||
| mmu-hash64.c | ||
| mmu-hash64.h | ||
| mmu-radix64.c | ||
| mmu-radix64.h | ||
| monitor.c | ||
| power8-pmu-regs.c.inc | ||
| power8-pmu.c | ||
| power8-pmu.h | ||
| spr_common.h | ||
| tcg-stub.c | ||
| timebase_helper.c | ||
| trace-events | ||
| trace.h | ||
| translate.c | ||
| user_only_helper.c | ||