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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 30007C433DB for ; Thu, 4 Feb 2021 13:46:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F225F64DE7 for ; Thu, 4 Feb 2021 13:46:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236441AbhBDNqQ (ORCPT ); Thu, 4 Feb 2021 08:46:16 -0500 Received: from mx2.suse.de ([195.135.220.15]:56822 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236428AbhBDNo2 (ORCPT ); Thu, 4 Feb 2021 08:44:28 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id A5427AD0B; Thu, 4 Feb 2021 13:43:45 +0000 (UTC) From: Oscar Salvador To: akpm@linux-foundation.org Cc: David Hildenbrand , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Oscar Salvador Subject: [PATCH v3 3/3] x86/vmemmap: Handle unpopulated sub-pmd ranges Date: Thu, 4 Feb 2021 14:43:25 +0100 Message-Id: <20210204134325.7237-4-osalvador@suse.de> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20210204134325.7237-1-osalvador@suse.de> References: <20210204134325.7237-1-osalvador@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When the size of a struct page is not multiple of 2MB, sections do not span a PMD anymore and so when populating them some parts of the PMD will remain unused. Because of this, PMDs will be left behind when depopulating sections since remove_pmd_table() thinks that those unused parts are still in use. Fix this by marking the unused parts with PAGE_UNUSED, so memchr_inv() will do the right thing and will let us free the PMD when the last user of it is gone. This patch is based on a similar patch by David Hildenbrand: https://lore.kernel.org/linux-mm/20200722094558.9828-9-david@redhat.com/ https://lore.kernel.org/linux-mm/20200722094558.9828-10-david@redhat.com/ Signed-off-by: Oscar Salvador --- arch/x86/mm/init_64.c | 106 ++++++++++++++++++++++++++++++++++++++---- 1 file changed, 98 insertions(+), 8 deletions(-) diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 9ecb3c488ac8..7e8de63f02b3 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -871,7 +871,93 @@ int arch_add_memory(int nid, u64 start, u64 size, return add_pages(nid, start_pfn, nr_pages, params); } -#define PAGE_INUSE 0xFD +#ifdef CONFIG_SPARSEMEM_VMEMMAP +#define PAGE_UNUSED 0xFD + +/* + * The unused vmemmap range, which was not yet memset(PAGE_UNUSED) ranges + * from unused_pmd_start to next PMD_SIZE boundary. + */ +static unsigned long unused_pmd_start __meminitdata; + +static void __meminit vmemmap_flush_unused_pmd(void) +{ + if (!unused_pmd_start) + return; + /* + * Clears (unused_pmd_start, PMD_END] + */ + memset((void *)unused_pmd_start, PAGE_UNUSED, + ALIGN(unused_pmd_start, PMD_SIZE) - unused_pmd_start); + unused_pmd_start = 0; +} + +/* Returns true if the PMD is completely unused and thus it can be freed */ +static bool __meminit vmemmap_unuse_sub_pmd(unsigned long addr, unsigned long end) +{ + unsigned long start = ALIGN_DOWN(addr, PMD_SIZE); + + vmemmap_flush_unused_pmd(); + memset((void *)addr, PAGE_UNUSED, end - addr); + + return !memchr_inv((void *)start, PAGE_UNUSED, PMD_SIZE); +} + +static void __meminit __vmemmap_use_sub_pmd(unsigned long start) +{ + /* + * As we expect to add in the same granularity as we remove, it's + * sufficient to mark only some piece used to block the memmap page from + * getting removed when removing some other adjacent memmap (just in + * case the first memmap never gets initialized e.g., because the memory + * block never gets onlined). + */ + memset((void *)start, 0, sizeof(struct page)); +} + +static void __meminit vmemmap_use_sub_pmd(unsigned long start, unsigned long end) +{ + /* + * We only optimize if the new used range directly follows the + * previously unused range (esp., when populating consecutive sections). + */ + if (unused_pmd_start == start) { + if (likely(IS_ALIGNED(end, PMD_SIZE))) + unused_pmd_start = 0; + else + unused_pmd_start = end; + return; + } + + vmemmap_flush_unused_pmd(); + __vmemmap_use_sub_pmd(start); +} + +static void __meminit vmemmap_use_new_sub_pmd(unsigned long start, unsigned long end) +{ + vmemmap_flush_unused_pmd(); + + /* + * Could be our memmap page is filled with PAGE_UNUSED already from a + * previous remove. + */ + __vmemmap_use_sub_pmd(start); + + /* + * Mark the unused parts of the new memmap range + */ + if (!IS_ALIGNED(start, PMD_SIZE)) + memset((void *)start, PAGE_UNUSED, + start - ALIGN_DOWN(start, PMD_SIZE)); + /* + * We want to avoid memset(PAGE_UNUSED) when populating the vmemmap of + * consecutive sections. Remember for the last added PMD the last + * unused range in the populated PMD. + */ + if (!IS_ALIGNED(end, PMD_SIZE)) + unused_pmd_start = end; +} +#endif static void __meminit free_pagetable(struct page *page, int order) { @@ -1006,7 +1092,6 @@ remove_pmd_table(pmd_t *pmd_start, unsigned long addr, unsigned long end, unsigned long next, pages = 0; pte_t *pte_base; pmd_t *pmd; - void *page_addr; pmd = pmd_start + pmd_index(addr); for (; addr < end; addr = next, pmd++) { @@ -1027,12 +1112,11 @@ remove_pmd_table(pmd_t *pmd_start, unsigned long addr, unsigned long end, spin_unlock(&init_mm.page_table_lock); pages++; } else { - /* If here, we are freeing vmemmap pages. */ - memset((void *)addr, PAGE_INUSE, next - addr); - - page_addr = page_address(pmd_page(*pmd)); - if (!memchr_inv(page_addr, PAGE_INUSE, - PMD_SIZE)) { +#ifdef CONFIG_SPARSEMEM_VMEMMAP + /* + * Free the PMD if the whole range is unused. + */ + if (vmemmap_unuse_sub_pmd(addr, next)) { free_hugepage_table(pmd_page(*pmd), altmap); @@ -1040,6 +1124,7 @@ remove_pmd_table(pmd_t *pmd_start, unsigned long addr, unsigned long end, pmd_clear(pmd); spin_unlock(&init_mm.page_table_lock); } +#endif } continue; @@ -1492,11 +1577,16 @@ static int __meminit vmemmap_populate_hugepages(unsigned long start, addr_end = addr + PMD_SIZE; p_end = p + PMD_SIZE; + + if (!IS_ALIGNED(addr, PMD_SIZE) || + !IS_ALIGNED(next, PMD_SIZE)) + vmemmap_use_new_sub_pmd(addr, next); continue; } else if (altmap) return -ENOMEM; /* no fallback */ } else if (pmd_large(*pmd)) { vmemmap_verify((pte_t *)pmd, node, addr, next); + vmemmap_use_sub_pmd(addr, next); continue; } if (vmemmap_populate_basepages(addr, next, node, NULL)) -- 2.26.2