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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DDE07C44516 for ; Thu, 16 Jul 2026 15:04:43 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8B5E26B0126; Thu, 16 Jul 2026 11:04:37 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 840566B0128; Thu, 16 Jul 2026 11:04:37 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 755D46B0129; Thu, 16 Jul 2026 11:04:37 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 3DFB76B0126 for ; Thu, 16 Jul 2026 11:04:37 -0400 (EDT) Received: from smtpin21.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay05.hostedemail.com (Postfix) with ESMTP id A5D5540203 for ; Thu, 16 Jul 2026 15:04:36 +0000 (UTC) X-FDA: 84994961352.21.332EE93 Received: from mail-yw1-f178.google.com (mail-yw1-f178.google.com [209.85.128.178]) by imf19.hostedemail.com (Postfix) with ESMTP id C4C091A0004 for ; Thu, 16 Jul 2026 15:04:34 +0000 (UTC) Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=soleen.com header.s=google header.b=KlPRBD5C; spf=pass (imf19.hostedemail.com: domain of pasha.tatashin@soleen.com designates 209.85.128.178 as permitted sender) smtp.mailfrom=pasha.tatashin@soleen.com; dmarc=pass (policy=reject) header.from=soleen.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1784214274; b=xzHArVwpOrOgQIc3lOf5yWollG+Eedmwdt6NIHUWgvTGlIa1Wg97plGsPGaE3C7Uf6xszO TZoG4iylpGIgn0DVQfi1Ooq+WwY+NJRbvYyF2jKkwpu38pDqNRTXcv/2j+WZV29Ocw4dUV FMttiOeBjeIxfdSOoJszGppAJyauCgw= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=soleen.com header.s=google header.b=KlPRBD5C; spf=pass (imf19.hostedemail.com: domain of pasha.tatashin@soleen.com designates 209.85.128.178 as permitted sender) smtp.mailfrom=pasha.tatashin@soleen.com; dmarc=pass (policy=reject) header.from=soleen.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1784214274; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=ESEHmQjCMBnGaENVOX4xB1tescWaluk9TL1CPIBeov4=; b=shfU4ikAxob80VNVdzO+RogmSA3rMRnGcLEeYaBYULZdR4W0i5Y3TyAfc5YA/S6BL0vgv0 Yhw5AE72PDRW/JFN59C8th6k4flfeLpwTZplcey0I/F6Oig8H9S36Q6RCZ0R+/DczNQhlX 5dyRlCCa5wVlssrda9pnUslbo9N1RCc= Received: by mail-yw1-f178.google.com with SMTP id 00721157ae682-81ec29f1d07so34966547b3.1 for ; Thu, 16 Jul 2026 08:04:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=soleen.com; s=google; t=1784214274; x=1784819074; darn=kvack.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=ESEHmQjCMBnGaENVOX4xB1tescWaluk9TL1CPIBeov4=; b=KlPRBD5CFc+U14Cq1AeOKm5yTMgh/cZT9sNS9OpBSpIod4+onZBQFTnFJlXTyZz1ZI NP+YP63f+mdLW3zU92WrmjfO7tQ+iXcJAgOxwC0DSnHEq1xum5/QbjKIQwm9jLO7nl4q 3/87+tIQoeAu2azkn8cjtjuTp142BnlxWqVhUhEOgyzJ1PcV1uc7zeDfREvvXyX/UXPR zo6x6MemgdBwsv3Bgk6/oDbXXvwDkbRnkQ/SM8QMpESdcHkl2X/DT1RrgEr579VDpUJ9 vpRtbwsNdxT8vS+YFlP+OO/w//17+yoKPVQ2ebuKEg447Bc9rzbI6UN4GNNj5K/E623F aHiQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1784214274; x=1784819074; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=ESEHmQjCMBnGaENVOX4xB1tescWaluk9TL1CPIBeov4=; b=KJjGufteciyCG3mECgXun4tVx7YR4pbMX42x7Z3uKaE61nmjj4ETakQsbSFAUGtHvh CDg2CuPG2/8S0rkNxSXLrYVJaTSjfOfHiyvPuc8vdnTmVwx9vSL9NOoTCFNkdTY/hvvN inxMBmH4g+aW895pytOIqFQePGjIPJ+9duvGNmURtUpQ012gShUs1RrSnTucgZzulBxN hDJHDqTXIgfo+oNKrYmovhEIs7Wj9VQlWYCjXgR+sRam/+C9xUX6UtGnYmo2P90nr5jP mJpubHtHSB00Bw6cYBQT46tUQe9Tsplfqm/CsM2qGq2AYB/k4072EIkqClei4WOIxNKU WNhw== X-Forwarded-Encrypted: i=1; AHgh+RrYeahHE3pIO4zA4vNUd2/N5wwhjdztRvgv1zFlU3BO6PPzAxJLVfPl6iKiyWxctfs62Cu3n3eonQ==@kvack.org X-Gm-Message-State: AOJu0YzAnch1JT9uCsymnsQyi02imujILkd4zjbBjTCEjrLuiY/srFZ3 MQpycv3z8V/7aBmFNG0uUtY3vMHOew2VB9hCVYEVcZQCErW+P4x3ix9aJIsFpRVjQmg= X-Gm-Gg: AfdE7cmowcyD576Ux3axNmiX5iqkGPshphC9gRff9lI/JGegankAKCfRlMnmcvCc9Xw DfyGMNhlkiM3XLKvhxfbLWccs5G2OFzR0G8WRv13m9VtmOImF9iGWLV8qqRHoWYHGAQCSqaJ2ah VChPgTBnHVA6Pg+yddqkYt5AxLOHKNyyLCDVv9fALbb652s4L3TYUAScC15Pmqp4jbs6n8oXgrf eoV+cG81Fa1b8NC99M/0nMMqYfH/LswJ/dReLpRD3V/L+oKADuSsd4uP65dF50PcmGtMjzL2qTT q3Ms8ww3iRuLmXJSt0U77GiPzV34YqsVZ263uyTcNV/2+FGcBIlazQ4WfEsiQsy1qGnVNXxcQiV 1lLxa/aloqdI6pw2sfzceqShGi0fVjitoiN6mU3CxwVSU2hV4rEaVL/U9ZsD93s2PWQCaCpPgqJ DDUhRimFigIgiSsccpXIaAFgBe9PmikZEkPANNoo2H/enRXsemcoyfvb2apCeCDhcxvmtNnS1ki gQVTw6P+fxf X-Received: by 2002:a05:690c:22c9:b0:7f8:7e50:6390 with SMTP id 00721157ae682-81ebb28d493mr96938907b3.50.1784214273078; Thu, 16 Jul 2026 08:04:33 -0700 (PDT) Received: from google.com (138.200.150.34.bc.googleusercontent.com. [34.150.200.138]) by smtp.gmail.com with ESMTPSA id 00721157ae682-81e6c23d1afsm198963407b3.47.2026.07.16.08.04.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Jul 2026 08:04:32 -0700 (PDT) Date: Thu, 16 Jul 2026 11:04:31 -0400 From: Pasha Tatashin To: Mike Rapoport Cc: Michal Clapinski , Pasha Tatashin , Pratyush Yadav , Alexander Graf , Evangelos Petrongonas , kexec@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] kho: align kho_scratch to MAX_ORDER_NR_PAGES pages Message-ID: References: <20260714205111.2497151-1-mclapinski@google.com> <178409777790.255896.16691338963510282908.b4-review@b4> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <178409777790.255896.16691338963510282908.b4-review@b4> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: C4C091A0004 X-Stat-Signature: qz5jzc4hz9bx8m65i7whph13cbeob8cn X-HE-Tag: 1784214274-662739 X-HE-Meta: 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 MqGGv+2U LkxHSVP9dau7a0c+FmKp6+BjRaOLIJ9+Pq2BMYo+v0Lloq2WbD7J9+QHecbSfsaJP1BPuJs8UORBQ0JvVQS0KxfnCUo/tTvFIEdefSEtAKo+VBqz6KMirG6IQPnlqnAUvSLwcSAYy8e43bb9yXCRWGUo3rGk98XPNIaySVJetPfizzG8C5LqcRBrpiCZ0UQg4fBDX/b+69Pp1D+9nKr5wvuMKSjG2kMHYPB3NQTu1CglAFXVTtHZP2RRxBbgp7SZG6sHavL6rPZRysA6WyVgSnBxpE0DCKdMG43xq3ge1mhLs0hkqyg6O9FlioQ9ehcWhZxX/YNZd24IsFSXDxRHkIjuw3UyA2YCg4k4BopbbJy05CCxhY2T2N3k4SA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 07-15 09:42, Mike Rapoport wrote: > Hi Michal, > > > I caught this crash: > > BUG: unable to handle page fault for address: ff19164fffff8328 > > RIP: 0010:__free_one_page+0x1a1/0x6b0 > > Call Trace: > > > > [] free_one_page+0xaf/0x240 > > [] deferred_free_pages+0xa8/0xd0 > > [] deferred_init_memmap_chunk+0x10f/0x1b0 > > [] padata_mt_helper+0x65/0xa0 > > [] process_scheduled_works+0x202/0x410 > > [] worker_thread+0x1f9/0x2d0 > > [] kthread+0x27d/0x2f0 > > [] ? __pfx_worker_thread+0x10/0x10 > > [] ? __pfx_kthread+0x10/0x10 > > [] ret_from_fork+0x145/0x280 > > [] ? __pfx_kthread+0x10/0x10 > > [] ret_from_fork_asm+0x1a/0x30 > > > > > > deferred_init_memmap_chunk() works fine without KHO because free > > regions will never be neighbors. However, with KHO, free memory > > will be split into (free && scratch) and (free && !scratch). > > KHO scratch is aligned to CMA_MIN_ALIGNMENT_BYTES (which on my setup > > is equal to 1 << 9 pages) but buddy can look at the neighborhood of > > MAX_ORDER_NR_PAGES pages (which is equal to 1 << 10 pages). > > This sometimes crashes when one half of the neighborhood is being > > initialized but the other part is yet to be initialized. > > > > To fix this, let's just align KHO scratch to MAX_ORDER_NR_PAGES pages. > > > > Fixes: c6073743d0c7 ("kho: make preserved pages compatible with deferred struct page init") > > Signed-off-by: Michal Clapinski > > > > diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c > > index 4834a809985ab..50928aaa33710 100644 > > --- a/kernel/liveupdate/kexec_handover.c > > +++ b/kernel/liveupdate/kexec_handover.c > > @@ -38,6 +38,16 @@ > > #include "../kexec_internal.h" > > #include "kexec_handover_internal.h" > > > > +/* > > + * This is the minimal alignment required by deferred struct page init. > > + * deferred_init_memmap_chunk frees memory to the buddy allocator, which looks > > + * at the neighboring pages (up to MAX_PAGE_ORDER) to merge them. > > + * If KHO scratch is not aligned to that value, buddy can access uninitialized > > + * struct pages, which can cause a crash. > > + */ > > +#define SCRATCH_ALIGNMENT_BYTES (1 << (PAGE_SHIFT + MAX_PAGE_ORDER)) > > +static_assert(SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES); > > Maybe make it a variable and set it at runtime? > We won't need to worry about different confugurations that override > MAX_ORDER and potentail divergence of pageblock size from MAX_ORDER in Do those architectures reduce MAX_ORDER when they override it? I would hope we could set the alignment once and make it large enough to work everywhere, rather than depending on dynamic changes even during boot... > the future. > > -- > Sincerely yours, > Mike. >