From patchwork Wed Dec 15 14:56:25 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Woodhouse X-Patchwork-Id: 12678503 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 32D1AC433FE for ; Wed, 15 Dec 2021 14:57:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243641AbhLOO5h (ORCPT ); Wed, 15 Dec 2021 09:57:37 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56622 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243636AbhLOO5F (ORCPT ); Wed, 15 Dec 2021 09:57:05 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2C13CC061751; Wed, 15 Dec 2021 06:57:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=t2pDyF9HlQXxBdiqGoBBzI2HbMJFOJNGsErAvpwpL8w=; b=q5UKw9lwQpDCPq1F5CZm91rqFI rrS51RgWzyboIZ9hEirjGwm5E2Y3ec5Xo3gnDy6LMLfPdiWaN7iRwwuw/J6H9+nHH/11P3Cp/OR4x N0RTh+n0r8OX4GQvitPo64ZroJxq2P2sOegny3PIwoVum/ISwUvI7jrZuItmvywwFGBPhVcCwSUwc OMTYRgBGgY9QPxgc7wLh+24GUQzvgShBSOfFy1jNfN5ELcodynYRWpUISakChBfmSgvIL1Nk5Ozeb 16/aNdPDWQkAWTrTK5GRgFpNOZyhrBM30jNCug5XjlCwsP9/8Ey6wy98LbvM7+MMT7ehwSQRqQCNd uKWrcDXQ==; Received: from i7.infradead.org ([2001:8b0:10b:1:21e:67ff:fecb:7a92]) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mxVhq-00EjwM-JA; Wed, 15 Dec 2021 14:56:35 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1mxVhq-0001Ng-Q6; Wed, 15 Dec 2021 14:56:34 +0000 From: David Woodhouse To: Thomas Gleixner Cc: Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" , Paolo Bonzini , "Paul E . McKenney" , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, rcu@vger.kernel.org, mimoja@mimoja.de, hewenliang4@huawei.com, hushiyuan@huawei.com, luolongjun@huawei.com, hejingxian@huawei.com Subject: [PATCH v3 1/9] x86/apic/x2apic: Fix parallel handling of cluster_mask Date: Wed, 15 Dec 2021 14:56:25 +0000 Message-Id: <20211215145633.5238-2-dwmw2@infradead.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20211215145633.5238-1-dwmw2@infradead.org> References: <20211215145633.5238-1-dwmw2@infradead.org> MIME-Version: 1.0 Sender: David Woodhouse X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: David Woodhouse For each CPU being brought up, the alloc_clustermask() function allocates a new struct cluster_mask just in case it's needed. Then the target CPU actually runs, and in init_x2apic_ldr() it either uses a cluster_mask from a previous CPU in the same cluster, or consumes the "spare" one and sets the global pointer to NULL. That isn't going to parallelise stunningly well. Ditch the global variable, let alloc_clustermask() install the struct *directly* in the per_cpu data for the CPU being brought up. As an optimisation, actually make it do so for *all* present CPUs in the same cluster, which means only one iteration over for_each_present_cpu() instead of doing so repeatedly, once for each CPU. Now, in fact, there's no point in the 'node' or 'clusterid' members of the struct cluster_mask, so just kill it and use struct cpumask instead. This was a harmless "bug" while CPU bringup wasn't actually happening in parallel. It's about to become less harmless... Fixes: 023a611748fd5 ("x86/apic/x2apic: Simplify cluster management") Signed-off-by: David Woodhouse --- arch/x86/kernel/apic/x2apic_cluster.c | 108 +++++++++++++++----------- 1 file changed, 62 insertions(+), 46 deletions(-) diff --git a/arch/x86/kernel/apic/x2apic_cluster.c b/arch/x86/kernel/apic/x2apic_cluster.c index e696e22d0531..e116dfaf5922 100644 --- a/arch/x86/kernel/apic/x2apic_cluster.c +++ b/arch/x86/kernel/apic/x2apic_cluster.c @@ -9,11 +9,7 @@ #include "local.h" -struct cluster_mask { - unsigned int clusterid; - int node; - struct cpumask mask; -}; +#define apic_cluster(apicid) ((apicid) >> 4) /* * __x2apic_send_IPI_mask() possibly needs to read @@ -23,8 +19,7 @@ struct cluster_mask { static u32 *x86_cpu_to_logical_apicid __read_mostly; static DEFINE_PER_CPU(cpumask_var_t, ipi_mask); -static DEFINE_PER_CPU_READ_MOSTLY(struct cluster_mask *, cluster_masks); -static struct cluster_mask *cluster_hotplug_mask; +static DEFINE_PER_CPU_READ_MOSTLY(struct cpumask *, cluster_masks); static int x2apic_acpi_madt_oem_check(char *oem_id, char *oem_table_id) { @@ -60,10 +55,10 @@ __x2apic_send_IPI_mask(const struct cpumask *mask, int vector, int apic_dest) /* Collapse cpus in a cluster so a single IPI per cluster is sent */ for_each_cpu(cpu, tmpmsk) { - struct cluster_mask *cmsk = per_cpu(cluster_masks, cpu); + struct cpumask *cmsk = per_cpu(cluster_masks, cpu); dest = 0; - for_each_cpu_and(clustercpu, tmpmsk, &cmsk->mask) + for_each_cpu_and(clustercpu, tmpmsk, cmsk) dest |= x86_cpu_to_logical_apicid[clustercpu]; if (!dest) @@ -71,7 +66,7 @@ __x2apic_send_IPI_mask(const struct cpumask *mask, int vector, int apic_dest) __x2apic_send_IPI_dest(dest, vector, APIC_DEST_LOGICAL); /* Remove cluster CPUs from tmpmask */ - cpumask_andnot(tmpmsk, tmpmsk, &cmsk->mask); + cpumask_andnot(tmpmsk, tmpmsk, cmsk); } local_irq_restore(flags); @@ -105,55 +100,76 @@ static u32 x2apic_calc_apicid(unsigned int cpu) static void init_x2apic_ldr(void) { - struct cluster_mask *cmsk = this_cpu_read(cluster_masks); - u32 cluster, apicid = apic_read(APIC_LDR); - unsigned int cpu; + struct cpumask *cmsk = this_cpu_read(cluster_masks); - x86_cpu_to_logical_apicid[smp_processor_id()] = apicid; + BUG_ON(!cmsk); - if (cmsk) - goto update; - - cluster = apicid >> 16; - for_each_online_cpu(cpu) { - cmsk = per_cpu(cluster_masks, cpu); - /* Matching cluster found. Link and update it. */ - if (cmsk && cmsk->clusterid == cluster) - goto update; + cpumask_set_cpu(smp_processor_id(), cmsk); +} + +/* + * As an optimisation during boot, set the cluster_mask for *all* + * present CPUs at once, to prevent *each* of them having to iterate + * over the others to find the existing cluster_mask. + */ +static void prefill_clustermask(struct cpumask *cmsk, u32 cluster) +{ + int cpu; + + for_each_present_cpu(cpu) { + u32 apicid = apic->cpu_present_to_apicid(cpu); + if (apicid != BAD_APICID && apic_cluster(apicid) == cluster) { + struct cpumask **cpu_cmsk = &per_cpu(cluster_masks, cpu); + + BUG_ON(*cpu_cmsk && *cpu_cmsk != cmsk); + *cpu_cmsk = cmsk; + } } - cmsk = cluster_hotplug_mask; - cmsk->clusterid = cluster; - cluster_hotplug_mask = NULL; -update: - this_cpu_write(cluster_masks, cmsk); - cpumask_set_cpu(smp_processor_id(), &cmsk->mask); } -static int alloc_clustermask(unsigned int cpu, int node) +static int alloc_clustermask(unsigned int cpu, u32 cluster, int node) { + struct cpumask *cmsk = NULL; + unsigned int cpu_i; + u32 apicid; + if (per_cpu(cluster_masks, cpu)) return 0; - /* - * If a hotplug spare mask exists, check whether it's on the right - * node. If not, free it and allocate a new one. - */ - if (cluster_hotplug_mask) { - if (cluster_hotplug_mask->node == node) - return 0; - kfree(cluster_hotplug_mask); + + /* For the hotplug case, don't always allocate a new one */ + if (system_state >= SYSTEM_RUNNING) { + for_each_present_cpu(cpu_i) { + apicid = apic->cpu_present_to_apicid(cpu_i); + if (apicid != BAD_APICID && apic_cluster(apicid) == cluster) { + cmsk = per_cpu(cluster_masks, cpu_i); + if (cmsk) + break; + } + } + } + if (!cmsk) { + cmsk = kzalloc_node(sizeof(*cmsk), GFP_KERNEL, node); + if (!cmsk) + return -ENOMEM; } - cluster_hotplug_mask = kzalloc_node(sizeof(*cluster_hotplug_mask), - GFP_KERNEL, node); - if (!cluster_hotplug_mask) - return -ENOMEM; - cluster_hotplug_mask->node = node; + per_cpu(cluster_masks, cpu) = cmsk; + + if (system_state < SYSTEM_RUNNING) + prefill_clustermask(cmsk, cluster); + return 0; } static int x2apic_prepare_cpu(unsigned int cpu) { - if (alloc_clustermask(cpu, cpu_to_node(cpu)) < 0) + u32 phys_apicid = apic->cpu_present_to_apicid(cpu); + u32 cluster = apic_cluster(phys_apicid); + u32 logical_apicid = (cluster << 16) | (1 << (phys_apicid & 0xf)); + + x86_cpu_to_logical_apicid[cpu] = logical_apicid; + + if (alloc_clustermask(cpu, cluster, cpu_to_node(cpu)) < 0) return -ENOMEM; if (!zalloc_cpumask_var(&per_cpu(ipi_mask, cpu), GFP_KERNEL)) return -ENOMEM; @@ -162,10 +178,10 @@ static int x2apic_prepare_cpu(unsigned int cpu) static int x2apic_dead_cpu(unsigned int dead_cpu) { - struct cluster_mask *cmsk = per_cpu(cluster_masks, dead_cpu); + struct cpumask *cmsk = per_cpu(cluster_masks, dead_cpu); if (cmsk) - cpumask_clear_cpu(dead_cpu, &cmsk->mask); + cpumask_clear_cpu(dead_cpu, cmsk); free_cpumask_var(per_cpu(ipi_mask, dead_cpu)); return 0; }