Messages in this thread Patch in this message | | | From | Sebastian Andrzej Siewior <> | Subject | [PATCH 2/2] cpu/hotplug: Allow the CPU in CPU_UP_PREPARE state to be brought up again. | Date | Mon, 6 Dec 2021 16:20:34 +0100 |
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From: "Longpeng(Mike)" <longpeng2@huawei.com>
A CPU will not show up in virtualized environment which includes an Enclave. The VM splits its resources into a primary VM and a Enclave VM. While the Enclave is active, the hypervisor will ignore all requests to bring up a CPU and this CPU will remain in CPU_UP_PREPARE state. The kernel will wait up to ten seconds for CPU to show up (do_boot_cpu()) and then rollback the hotplug state back to CPUHP_OFFLINE leaving the CPU state in CPU_UP_PREPARE. The CPU state is set back to CPUHP_TEARDOWN_CPU during the CPU_POST_DEAD stage.
After the Enclave VM terminates, the primary VM can bring up the CPU again.
Allow to bring up the CPU if it is in the CPU_UP_PREPARE state.
[bigeasy: Rewrite commit description.]
Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Link: https://lore.kernel.org/r/20210901051143.2752-1-longpeng2@huawei.com Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Tested-by: Dongli Zhang <dongli.zhang@oracle.com> Reviewed-by: Henry Wang <Henry.Wang@arm.com> Link: https://lore.kernel.org/r/20211122154714.xaoxok3fpk5bgznz@linutronix.de --- kernel/smpboot.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/kernel/smpboot.c b/kernel/smpboot.c index f6bc0bc8a2aab..b9f54544e7499 100644 --- a/kernel/smpboot.c +++ b/kernel/smpboot.c @@ -392,6 +392,13 @@ int cpu_check_up_prepare(int cpu) */ return -EAGAIN; + case CPU_UP_PREPARE: + /* + * Timeout while waiting for the CPU to show up. Allow to try + * again later. + */ + return 0; + default: /* Should not happen. Famous last words. */ -- 2.34.1
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