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 X-Spam-Level: X-Spam-Status: No, score=-10.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D3248C433E0 for ; Fri, 26 Jun 2020 09:35:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A3F84212CC for ; Fri, 26 Jun 2020 09:35:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726725AbgFZJe6 (ORCPT ); Fri, 26 Jun 2020 05:34:58 -0400 Received: from 8bytes.org ([81.169.241.247]:50210 "EHLO theia.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726613AbgFZJe6 (ORCPT ); Fri, 26 Jun 2020 05:34:58 -0400 Received: by theia.8bytes.org (Postfix, from userid 1000) id 72182391; Fri, 26 Jun 2020 11:34:57 +0200 (CEST) From: Joerg Roedel To: x86@kernel.org Cc: hpa@zytor.com, Dave Hansen , Andy Lutomirski , Peter Zijlstra , Andrew Morton , Steven Rostedt , joro@8bytes.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Joerg Roedel Subject: [PATCH] x86/mm: Pre-allocate p4d/pud pages for vmalloc area Date: Fri, 26 Jun 2020 11:34:50 +0200 Message-Id: <20200626093450.27741-1-joro@8bytes.org> X-Mailer: git-send-email 2.17.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Joerg Roedel Pre-allocate the page-table pages for the vmalloc area at the level which needs synchronization on x86. This is P4D for 5-level and PUD for 4-level paging. Doing this at boot makes sure all page-tables in the system have these pages already and do not need to be synchronized at runtime. The runtime synchronizatin takes the pgd_lock and iterates over all page-tables in the system, so it can take quite long and is better avoided. Signed-off-by: Joerg Roedel --- arch/x86/mm/init_64.c | 55 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index dbae185511cd..475a4008445b 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -1238,6 +1238,59 @@ static void __init register_page_bootmem_info(void) #endif } +/* + * Pre-allocates page-table pages for the vmalloc area in the kernel page-table. + * Only the level which needs to be synchronized between all page-tables is + * allocated because the synchronization can be expensive. + */ +static void __init preallocate_vmalloc_pages(void) +{ + unsigned long addr; + const char *lvl; + int count = 0; + + for (addr = VMALLOC_START; addr <= VMALLOC_END; addr = ALIGN(addr + 1, PGDIR_SIZE)) { + pgd_t *pgd = pgd_offset_k(addr); + p4d_t *p4d; + pud_t *pud; + + p4d = p4d_offset(pgd, addr); + if (p4d_none(*p4d)) { + /* Can only happen with 5-level paging */ + p4d = p4d_alloc(&init_mm, pgd, addr); + if (!p4d) { + lvl = "p4d"; + goto failed; + } + count += 1; + } + + if (pgtable_l5_enabled()) + continue; + + pud = pud_offset(p4d, addr); + if (pud_none(*pud)) { + /* Ends up here only with 4-level paging */ + pud = pud_alloc(&init_mm, p4d, addr); + if (!pud) { + lvl = "pud"; + goto failed; + } + count += 1; + } + } + + return; + +failed: + + /* + * A failure here is not fatal - If the pages can be allocated later it + * will be synchronized to other page-tables. + */ + pr_err("Failed to pre-allocate %s pages for vmalloc area\n", lvl); +} + void __init mem_init(void) { pci_iommu_alloc(); @@ -1261,6 +1314,8 @@ void __init mem_init(void) if (get_gate_vma(&init_mm)) kclist_add(&kcore_vsyscall, (void *)VSYSCALL_ADDR, PAGE_SIZE, KCORE_USER); + preallocate_vmalloc_pages(); + mem_init_print_info(NULL); } -- 2.27.0