The following commit has been merged into the smp/core branch of tip: Commit-ID: c7dfb2591b23856182e2c9da6b1d526ef7fd6b2e Gitweb: https://git.kernel.org/tip/c7dfb2591b23856182e2c9da6b1d526ef7fd6b2e Author: Longpeng(Mike) <longpeng2@xxxxxxxxxx> AuthorDate: Wed, 09 Feb 2022 09:02:14 +01:00 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitterDate: Tue, 12 Apr 2022 14:13:01 +02:00 cpu/hotplug: Allow the CPU in CPU_UP_PREPARE state to be brought up again. 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@xxxxxxxxxx> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Tested-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx> Reviewed-by: Valentin Schneider <valentin.schneider@xxxxxxx> Reviewed-by: Henry Wang <Henry.Wang@xxxxxxx> Link: https://lore.kernel.org/r/20220209080214.1439408-3-bigeasy@xxxxxxxxxxxxx --- kernel/smpboot.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/smpboot.c b/kernel/smpboot.c index f6bc0bc..b9f5454 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. */
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