From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AB8JxZoEuKNi7OebnylHNcEQL149wChwCWbRugR7/7VPo7av7AM9Xp5cbP+KCzEQfpseT+31c/1e ARC-Seal: i=1; a=rsa-sha256; t=1526937527; cv=none; d=google.com; s=arc-20160816; b=aNdfr6RM2/Fv/GpbBusLDHQyDngwczNbvhdjb+MY2Uha4+vnoqWqKGulWkKtrfKX0z IiJzGx/NCC5X9H8H57Hj0CQmEKGfxla35ivGtnCOIk4QUmd0Iv2Zmlco58uS42qjAie2 VJnp54AEidw7pKkjPz3yTnICr/RtpmHe9H5ZJh55joHhuBnw4k3DLvTKQZiJ9tMCuZxv i0vctXC2r5tHITKnYNloDXb/qg0H3Ey21s/8IkKS0ddfkqb22jCGdKo/PLilypi7ZU1q AaWtUk9LlKgz07vTqB3IkdDht2glRdmMArIQyRVnIycrDgoX12Shs7xgV8XJ68sFKYlf nBMw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:dkim-signature:arc-authentication-results; bh=IYlGglrxvdfk6oN+D1cR3zHoSsD7kHpncn0lp5Xe+D8=; b=02GUFvEEf/3EYhuaEtx4no849PAJaBDeRpcrb7yMQeR6Vu95P9vt92m5hCUAG7UY48 o1kHOXSMTF3+7bnLVTzsoMD15pr3sXES4QuNXL34tkKjDI3xHdoDn8CvhDlWLnBU+R8R 7Wukrpw6syPEJSBSRNgkzBFQQ8fi14f0ljR30U7Uj5+zv234OuItQlc2kBvbXhHOTQlt JVDni/RNyvXjX3T01HO5/j58+FjO9Fyn7RwKVEPbTRXvVmXxPj6FVJcHZwIh41ciK5nV 6H6BTpn3niC/buGrPEZnL+FSA8CBGoRdlXFoFeFGELPZ9DNw2HGpcgxfAUX/6yyANFrc Or8A== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=YwjlwoY2; spf=pass (google.com: domain of srs0=nia/=ii=linuxfoundation.org=gregkh@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=SRS0=nia/=II=linuxfoundation.org=gregkh@kernel.org Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=YwjlwoY2; spf=pass (google.com: domain of srs0=nia/=ii=linuxfoundation.org=gregkh@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=SRS0=nia/=II=linuxfoundation.org=gregkh@kernel.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Pavel Tatashin , Michal Hocko , Andrew Morton , Steven Sistare , Daniel Jordan , Mel Gorman , Fengguang Wu , Dennis Zhou , Linus Torvalds Subject: [PATCH 4.14 26/95] mm: dont allow deferred pages with NEED_PER_CPU_KM Date: Mon, 21 May 2018 23:11:16 +0200 Message-Id: <20180521210453.792478845@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180521210447.219380974@linuxfoundation.org> References: <20180521210447.219380974@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1601109869699407044?= X-GMAIL-MSGID: =?utf-8?q?1601110044675455507?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Pavel Tatashin commit ab1e8d8960b68f54af42b6484b5950bd13a4054b upstream. It is unsafe to do virtual to physical translations before mm_init() is called if struct page is needed in order to determine the memory section number (see SECTION_IN_PAGE_FLAGS). This is because only in mm_init() we initialize struct pages for all the allocated memory when deferred struct pages are used. My recent fix in commit c9e97a1997 ("mm: initialize pages on demand during boot") exposed this problem, because it greatly reduced number of pages that are initialized before mm_init(), but the problem existed even before my fix, as Fengguang Wu found. Below is a more detailed explanation of the problem. We initialize struct pages in four places: 1. Early in boot a small set of struct pages is initialized to fill the first section, and lower zones. 2. During mm_init() we initialize "struct pages" for all the memory that is allocated, i.e reserved in memblock. 3. Using on-demand logic when pages are allocated after mm_init call (when memblock is finished) 4. After smp_init() when the rest free deferred pages are initialized. The problem occurs if we try to do va to phys translation of a memory between steps 1 and 2. Because we have not yet initialized struct pages for all the reserved pages, it is inherently unsafe to do va to phys if the translation itself requires access of "struct page" as in case of this combination: CONFIG_SPARSE && !CONFIG_SPARSE_VMEMMAP The following path exposes the problem: start_kernel() trap_init() setup_cpu_entry_areas() setup_cpu_entry_area(cpu) get_cpu_gdt_paddr(cpu) per_cpu_ptr_to_phys(addr) pcpu_addr_to_page(addr) virt_to_page(addr) pfn_to_page(__pa(addr) >> PAGE_SHIFT) We disable this path by not allowing NEED_PER_CPU_KM with deferred struct pages feature. The problems are discussed in these threads: http://lkml.kernel.org/r/20180418135300.inazvpxjxowogyge@wfg-t540p.sh.intel.com http://lkml.kernel.org/r/20180419013128.iurzouiqxvcnpbvz@wfg-t540p.sh.intel.com http://lkml.kernel.org/r/20180426202619.2768-1-pasha.tatashin@oracle.com Link: http://lkml.kernel.org/r/20180515175124.1770-1-pasha.tatashin@oracle.com Fixes: 3a80a7fa7989 ("mm: meminit: initialise a subset of struct pages if CONFIG_DEFERRED_STRUCT_PAGE_INIT is set") Signed-off-by: Pavel Tatashin Acked-by: Michal Hocko Reviewed-by: Andrew Morton Cc: Steven Sistare Cc: Daniel Jordan Cc: Mel Gorman Cc: Fengguang Wu Cc: Dennis Zhou Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/Kconfig | 1 + 1 file changed, 1 insertion(+) --- a/mm/Kconfig +++ b/mm/Kconfig @@ -649,6 +649,7 @@ config DEFERRED_STRUCT_PAGE_INIT depends on ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT depends on NO_BOOTMEM && MEMORY_HOTPLUG depends on !FLATMEM + depends on !NEED_PER_CPU_KM help Ordinarily all struct pages are initialised during early boot in a single thread. On very large machines this can take a considerable