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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 03B31CE7A81 for ; Mon, 25 Sep 2023 07:54:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=jZPgp4w6T8x9q+PNYzzZPw9IHEG6/7YO4t9pXc37RBI=; b=zMTwuMlYBj27rt N40zUP2DobiNuTYF0V3h1Q9c3u+29hpD35xPvddoZqsHDU90NgoloiswqOgpU48EFSZMI0yO/I7i2 2AdflwvTIO1zyPS/Mtg6MSGEDJfIKxk5PRE5+z/hTJ9rJPbpSuDwJ8TNZ+4rssBiyxyrhWCZD7cHi rwjJUqzCebkp9RKIA7dkBrzKEUgb0RQgEe+kGDK87ykNJGRCCQWMPqGcD+T3yBovQk0VmmO9BI352 h3Gn++UubX/0zlfNgQCuUhZaeY8cB71IyAQHPkIatrJBW/LsT0O6KZ09XqDOL59K+RJn9+LpSQtPm A8IDCRpJ2na0MgMZuFiw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qkgQM-00DfOw-1T; Mon, 25 Sep 2023 07:54:34 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qkgQK-00DfNx-0P for kexec@lists.infradead.org; Mon, 25 Sep 2023 07:54:33 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1695628471; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=dvNFT/d/eIC1YCuTjJ6oHLqFtIHv+K5OABHBij7vEFw=; b=UIrOME1cNm/Qb3UiKXfuWe4pt7Kgj5/dw6M4IZ2OSmepcIcvP7dqW/MriCHQjo9GBKcN9s ioglJKf8KIEe0tc3tkAlScA6BO8d3ox2zn41l0EnDpbw/NOieaX7NbVDTU7WT+mGdy1avO lDQW529tkh2jBZnF7SFhGI9kIZO+D/A= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-615-EiVCJwtKPXe35uy12tmFnA-1; Mon, 25 Sep 2023 03:54:27 -0400 X-MC-Unique: EiVCJwtKPXe35uy12tmFnA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 505E785A5BE; Mon, 25 Sep 2023 07:54:27 +0000 (UTC) Received: from piliu.users.ipa.redhat.com (unknown [10.72.120.2]) by smtp.corp.redhat.com (Postfix) with ESMTP id 62A4540C6EA8; Mon, 25 Sep 2023 07:54:23 +0000 (UTC) From: Pingfan Liu To: linuxppc-dev@lists.ozlabs.org Cc: Pingfan Liu , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Mahesh Salgaonkar , Wen Xiong , Baoquan He , Ming Lei , kexec@lists.infradead.org Subject: [PATCHv7 4/4] powerpc/setup: alloc extra paca_ptrs to hold boot_cpuid Date: Mon, 25 Sep 2023 15:53:48 +0800 Message-Id: <20230925075348.16654-5-piliu@redhat.com> In-Reply-To: <20230925075348.16654-1-piliu@redhat.com> References: <20230925075348.16654-1-piliu@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230925_005432_237648_3877951F X-CRM114-Status: GOOD ( 16.70 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org paca_ptrs should be large enough to hold the boot_cpuid, hence, its lower boundary is set to the bigger one between boot_cpuid+1 and nr_cpus. On the other hand, some kernel component: -1. the timer assumes cpu0 online since the timer_list->flags subfield 'TIMER_CPUMASK' is zero if not initialized to a proper present cpu. -2. power9_idle_stop() assumes the primary thread's paca is allocated. Hence lift nr_cpu_ids from one to two to ensure cpu0 is onlined, if the boot cpu is not cpu0. Result: When nr_cpus=1, taskset -c 14 bash -c 'echo c > /proc/sysrq-trigger' the kdump kernel brings up two cpus. While when taskset -c 4 bash -c 'echo c > /proc/sysrq-trigger', the kdump kernel brings up one cpu. Signed-off-by: Pingfan Liu Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Christophe Leroy Cc: Mahesh Salgaonkar Cc: Wen Xiong Cc: Baoquan He Cc: Ming Lei Cc: kexec@lists.infradead.org To: linuxppc-dev@lists.ozlabs.org --- arch/powerpc/kernel/paca.c | 10 ++++++---- arch/powerpc/kernel/prom.c | 9 ++++++--- 2 files changed, 12 insertions(+), 7 deletions(-) diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c index cda4e00b67c1..91e2401de1bd 100644 --- a/arch/powerpc/kernel/paca.c +++ b/arch/powerpc/kernel/paca.c @@ -242,9 +242,10 @@ static int __initdata paca_struct_size; void __init allocate_paca_ptrs(void) { - paca_nr_cpu_ids = nr_cpu_ids; + int n = (boot_cpuid + 1) > nr_cpu_ids ? (boot_cpuid + 1) : nr_cpu_ids; - paca_ptrs_size = sizeof(struct paca_struct *) * nr_cpu_ids; + paca_nr_cpu_ids = n; + paca_ptrs_size = sizeof(struct paca_struct *) * n; paca_ptrs = memblock_alloc_raw(paca_ptrs_size, SMP_CACHE_BYTES); if (!paca_ptrs) panic("Failed to allocate %d bytes for paca pointers\n", @@ -287,13 +288,14 @@ void __init allocate_paca(int cpu) void __init free_unused_pacas(void) { int new_ptrs_size; + int n = (boot_cpuid + 1) > nr_cpu_ids ? (boot_cpuid + 1) : nr_cpu_ids; - new_ptrs_size = sizeof(struct paca_struct *) * nr_cpu_ids; + new_ptrs_size = sizeof(struct paca_struct *) * n; if (new_ptrs_size < paca_ptrs_size) memblock_phys_free(__pa(paca_ptrs) + new_ptrs_size, paca_ptrs_size - new_ptrs_size); - paca_nr_cpu_ids = nr_cpu_ids; + paca_nr_cpu_ids = n; paca_ptrs_size = new_ptrs_size; #ifdef CONFIG_PPC_64S_HASH_MMU diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c index 87272a2d8c10..15c994f54bf9 100644 --- a/arch/powerpc/kernel/prom.c +++ b/arch/powerpc/kernel/prom.c @@ -362,9 +362,12 @@ static int __init early_init_dt_scan_cpus(unsigned long node, */ boot_cpuid = i; found = true; - /* This works around the hole in paca_ptrs[]. */ - if (nr_cpu_ids < nthreads) - set_nr_cpu_ids(nthreads); + /* + * Ideally, nr_cpus=1 can be achieved if each kernel + * component does not assume cpu0 is onlined. + */ + if (boot_cpuid != 0 && nr_cpu_ids < 2) + set_nr_cpu_ids(2); } #ifdef CONFIG_SMP /* logical cpu id is always 0 on UP kernels */ -- 2.31.1 _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec