From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 77216C4332F for ; Mon, 6 Dec 2021 15:49:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1391927AbhLFPuq (ORCPT ); Mon, 6 Dec 2021 10:50:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59354 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1389328AbhLFPf5 (ORCPT ); Mon, 6 Dec 2021 10:35:57 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2EBA5C07E5F5 for ; Mon, 6 Dec 2021 07:20:59 -0800 (PST) From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1638804057; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=41Yw8yf+7TjYHl20/Q/EDf0gZtvNJ2sbLTnT1+NsteE=; b=LQgKbrKct/We7aHQ0TZFYlFpu0pNkOgrZ0sdarc6GLYKUkQoeNNAReN09czDjhMhsLh9te BX3g529ypr8U7D45FxquyLLsCnFTwa0E8VwTVABJ3Nz8tDiFDmwt9s65LduJcR/MYqdWBf TIlYLOsZZ356mha/P1VdYYQwPYgxszdT1xkJgZqKp7s4Q4jUgb4VTxhB2dRrgJejQ+s6Hu RG2ATWq0wWTu0Hp7ii/kr1uHYB2VoBrrmPiAeKTaaGoYw854rUmH3ZiCOjFfry6OfkAJFM QqoIe6pKucm2KTK3qWnikwFJv8x4UouEHovyaNHMt7s4xGg1BcQDOUnjW0tbtA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1638804057; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=41Yw8yf+7TjYHl20/Q/EDf0gZtvNJ2sbLTnT1+NsteE=; b=sxMj8+RWZBRXTITuDvoBALBqgfRKj9Zi74fNBcRPtr6Ur/ZuBm1c25eHa7tYX8nSmHpODY 3rlnDKXz8mPQb8Bg== To: linux-kernel@vger.kernel.org, x86@kernel.org, xen-devel@lists.xenproject.org Cc: Thomas Gleixner , Longpeng , Gonglei , Peter Zijlstra , Ingo Molnar , Valentin Schneider , Juergen Gross , Stefano Stabellini , Ingo Molnar , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , Sebastian Andrzej Siewior , Dongli Zhang , Henry Wang 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 Message-Id: <20211206152034.2150770-3-bigeasy@linutronix.de> In-Reply-To: <20211206152034.2150770-1-bigeasy@linutronix.de> References: <20211206152034.2150770-1-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Longpeng(Mike)" 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) Signed-off-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/r/20210901051143.2752-1-longpeng2@huawei.com Reviewed-by: Valentin Schneider Tested-by: Dongli Zhang Reviewed-by: Henry Wang 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; =20 + case CPU_UP_PREPARE: + /* + * Timeout while waiting for the CPU to show up. Allow to try + * again later. + */ + return 0; + default: =20 /* Should not happen. Famous last words. */ --=20 2.34.1