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 D3DDFD5E136 for ; Tue, 16 Dec 2025 11:57:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=EO58j438GWnjkv3vbMcJ669DRDtPdBQzG5P7oj/6KS8=; b=Lu31x5oeY0pGQfJEJ79pzl6HdQ k9LmPEDwbwKYTgsIyECMVmpTCR/gRe+8bTtTsxWjB9s5eUOVGUU1XOr+q1HYcbje8JH9tCd9KRYY7 oFk7QajSG0/U7LzF0qCrGuTOKqSqkFzd962JSYcSAQx9Nik/xwDPAxSwA7RXKAQxHd1gW+lbsSvqU 8qGUfL0KmguPDqr70DUQjOKypd4Upr9/bVmP/rfk4oQlZCa2teeMlopxhGTlwQN1ifoONEBQjvQRT jiXgTP8QKpotVfrNwFEgSn8Kpz13OWfFTf3xoNqirFi1pBVGhyqtlF9GpP2FZ6O+/JaUtlWjZVWp2 yjCtLtsA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vVTgH-000000059hX-3rmn; Tue, 16 Dec 2025 11:57:29 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vVTgG-000000059hK-0od3 for kexec@lists.infradead.org; Tue, 16 Dec 2025 11:57:28 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 202A0602C8; Tue, 16 Dec 2025 11:57:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B6FCAC4CEF1; Tue, 16 Dec 2025 11:57:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1765886246; bh=7ZFdnmw31SZNpKwCbTn3VwLXjfFQMOPztHlF9Mj4Qrc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=levK1FBGpysdmLQOMdTo0qNcTtB0s7RX0y4zTPIEcUboIVYrPZOuGFhUa6bo1W/fU Pkek4dlakV/QjzQcJYVYOoV/eRv457Rq1NkDVdejTSJwEFwt+UxkCc1PWpnmJO80LY OL/lhVJqjN+0W60eOuJJgkdiDtXm+r/RhggI5M/bwpZsNd03GHw3XpSEsQwOWig4A3 gBVT33D3IxuFbVGr9FbnmTvRhBd1ELZKiTNHPGscDsPTuppGV24iZQyq64K8sk0rYj SIdtnuzpZ8U/M8KggrJqRCjAmPMIXZl7O824bvxFkO6Vj/GpuSPgGhJSrKDsxcmuzD JbumRAVzfWYHg== Date: Tue, 16 Dec 2025 13:57:19 +0200 From: Mike Rapoport To: Evangelos Petrongonas Cc: Pasha Tatashin , Pratyush Yadav , Alexander Graf , Andrew Morton , Jason Miu , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org, nh-open-source@amazon.com Subject: Re: [PATCH] kho: add support for deferred struct page init Message-ID: References: <20251216084913.86342-1-epetron@amazon.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251216084913.86342-1-epetron@amazon.de> 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: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org Hi Evangelos, On Tue, Dec 16, 2025 at 08:49:12AM +0000, Evangelos Petrongonas wrote: > When `CONFIG_DEFERRED_STRUCT_PAGE_INIT` is enabled, struct page No need for markup formatting in the changelog. > initialization is deferred to parallel kthreads that run later > in the boot process. > > During KHO restoration, `deserialize_bitmap()` writes metadata for > each preserved memory region. However, if the struct page has not been > initialized, this write targets uninitialized memory, potentially > leading to errors like: > ``` > BUG: unable to handle page fault for address: ... > ``` > > Fix this by introducing `kho_get_preserved_page()`, which ensures > all struct pages in a preserved region are initialized by calling > `init_deferred_page()` which is a no-op when deferred init is disabled > or when the struct page is already initialized. > > Fixes: 8b66ed2c3f42 ("kho: mm: don't allow deferred struct page with KHO") > Signed-off-by: Evangelos Petrongonas > --- ... > +static struct page *__init kho_get_preserved_page(phys_addr_t phys, > + unsigned int order) > +{ > + unsigned long pfn = PHYS_PFN(phys); > + int nid = early_pfn_to_nid(pfn); > + > + for (int i = 0; i < (1 << order); i++) > + init_deferred_page(pfn + i, nid); This will skip pages below node->first_deferred_pfn, we need to use __init_page_from_nid() here. > + > + return pfn_to_page(pfn); > +} > + > static void __init deserialize_bitmap(unsigned int order, > struct khoser_mem_bitmap_ptr *elm) > { > @@ -449,7 +466,7 @@ static void __init deserialize_bitmap(unsigned int order, > int sz = 1 << (order + PAGE_SHIFT); > phys_addr_t phys = > elm->phys_start + (bit << (order + PAGE_SHIFT)); > - struct page *page = phys_to_page(phys); > + struct page *page = kho_get_preserved_page(phys, order); I think it's better to initialize deferred struct pages later in kho_restore_page. deserialize_bitmap() runs before SMP and it already does heavy lifting of memblock_reserve()s. Delaying struct page initialization until restore makes it at least run in parallel with other initialization tasks. I started to work on this just before plumbers and I have something untested here: https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git/log/?h=kho/deferred-page/v0.1 > union kho_page_info info; > > memblock_reserve(phys, sz); > -- > 2.43.0 > > > > > Amazon Web Services Development Center Germany GmbH > Tamara-Danz-Str. 13 > 10243 Berlin > Geschaeftsfuehrung: Christof Hellmis, Andreas Stieger > Eingetragen am Amtsgericht Charlottenburg unter HRB 257764 B > Sitz: Berlin > Ust-ID: DE 365 538 597 > -- Sincerely yours, Mike.