From patchwork Fri Jan 10 09:19:35 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Akihiko Odaki X-Patchwork-Id: 13934071 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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 1C80FE7719D for ; Fri, 10 Jan 2025 09:21:34 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tWBC8-0008Mw-83; Fri, 10 Jan 2025 04:20:44 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tWBBd-0007Yz-V3 for qemu-devel@nongnu.org; Fri, 10 Jan 2025 04:20:14 -0500 Received: from mail-pl1-x636.google.com ([2607:f8b0:4864:20::636]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1tWBBZ-0007aI-Ev for qemu-devel@nongnu.org; Fri, 10 Jan 2025 04:20:12 -0500 Received: by mail-pl1-x636.google.com with SMTP id d9443c01a7336-216728b1836so29702405ad.0 for ; Fri, 10 Jan 2025 01:20:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=daynix-com.20230601.gappssmtp.com; s=20230601; t=1736500807; x=1737105607; darn=nongnu.org; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:from:to:cc:subject:date:message-id :reply-to; bh=rab9AM6XE46IpCNkIWxpuZTQFO5WIkXW71J3f3qzs3Q=; b=PH01vXPt09J67q+eexH5dfJB3Ly2ASd+L+zvSnbYOlI0A/wPgYJ6YEwxrvI7Iaw8NR jUAtJVMATbxfHXx43HRS+S/f88KDxTbi7IsVty+Xg/m383vzFaaCOdvRlvlZw5X3++oz Oj6bTuc1NZ3t83JRtaPlzQNPx62wm39owyDBqyiIJde/69YQwVgiqlPK+BqBNqpYPKye tV7HthpD+ruc+vsG9/aepBjXWFQLo5t0C0n7l+UWZl9rtcrND7b7lU7BWtUQAak3NGlE oCChy0P82DoAiZxGZ0J3SveV6cApCJS3Nl2pxQ0Hn3b4DMtKQEyRwwqPIGUpYJj56g7q nnXw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1736500807; x=1737105607; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=rab9AM6XE46IpCNkIWxpuZTQFO5WIkXW71J3f3qzs3Q=; b=ptz6itbVDt+T8gu9oPhj45atbk1hv7SM2wMj+VNwMs4SSMthWX0M3nfyrWID0J8z2n EOvpHLeCpsTaxQkfwJ9/9Oq4K5TMdklzzdIckwdzjFCuN/nTY1EPnjD1AoOh4+JJxk2/ 7Z55iG+MVxEdPLFjg0CIk7F7vp+zRA+MXJc6rxFDJH4fAzy6xN0Qw7ECywVrnatb4wOk UG4PjbXI0qT39ZHaDgZ0cpf2+M1cr+5UlQAirsLjFQY7txy0MB5JV+3un4KqXKrgGVrm aWbzBAZC49gpZ1sVRtB2whVD+ZXgil+1Gk3E5Uj548dOnb0bEkBhFm1P+yAO4yaCsslu Jjew== X-Gm-Message-State: AOJu0YxrNHpmTeEXvpjehUU9rjm6zFwgh656itfz1ljDU48sKw97mUJX riDMI2x/nQ6OLl9d/sCTdfC4LTnwyV5GaF1vuYa1ZcFwlBBrD8yXwK7vyWwTuOs= X-Gm-Gg: ASbGncsfB9V+NYbGlbVZgy/5SsfRoXtv03GXXVrifdsdhNTWqivnGDig3rECtkhQSJS NbyzcXqRWXrGJwK4LTTkU2QSM8HBL4C6tolknlg3LBS3UJnQVFB0qo8witLHBRpIbBvYfMmQH9v RMTLyz5qU/n8WS4tmTT9rZ89YLxa+54BNU1XydFEsnzbSqsfLE9M3rte4JhZjSEPtXWxg3jvyZO TxisTKBKcKz8Dr3L5ZXUy6IcG2D4Q5sPx+vCeAfvd4MtCsjH5F51rv0cSw= X-Google-Smtp-Source: AGHT+IF7U9cLA0Vt6s08wzfiYTUJTv/5hvjEYLEUJlGUL2zH5dUT59pU+mFX+O3moJad/28l4Ok0vQ== X-Received: by 2002:a05:6a00:35c7:b0:725:f153:22d5 with SMTP id d2e1a72fcca58-72d21fd2f25mr14712760b3a.18.1736500806714; Fri, 10 Jan 2025 01:20:06 -0800 (PST) Received: from localhost ([157.82.203.37]) by smtp.gmail.com with UTF8SMTPSA id d2e1a72fcca58-72d406a77d5sm1164448b3a.171.2025.01.10.01.20.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 10 Jan 2025 01:20:06 -0800 (PST) From: Akihiko Odaki Date: Fri, 10 Jan 2025 18:19:35 +0900 Subject: [PATCH v8 2/2] memory: Do not create circular reference with subregion MIME-Version: 1.0 Message-Id: <20250110-san-v8-2-57a5a1be1bcf@daynix.com> References: <20250110-san-v8-0-57a5a1be1bcf@daynix.com> In-Reply-To: <20250110-san-v8-0-57a5a1be1bcf@daynix.com> To: Eduardo Habkost , Marcel Apfelbaum , =?utf-8?q?Philippe_Mathieu-?= =?utf-8?q?Daud=C3=A9?= , Yanan Wang , John Snow , BALATON Zoltan , Jiaxun Yang , Nicholas Piggin , Daniel Henrique Barboza , David Gibson , Harsh Prateek Bora , Alexey Kardashevskiy , "Michael S. Tsirkin" , =?utf-8?q?Alex_Benn=C3=A9e?= , Peter Xu , Fabiano Rosas , Paolo Bonzini , David Hildenbrand , Thomas Huth , Laurent Vivier , Peter Maydell Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, qemu-ppc@nongnu.org, devel@daynix.com, Akihiko Odaki X-Mailer: b4 0.14-dev-fd6e3 Received-SPF: pass client-ip=2607:f8b0:4864:20::636; envelope-from=akihiko.odaki@daynix.com; helo=mail-pl1-x636.google.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org memory_region_update_container_subregions() used to call memory_region_ref(), which creates a reference to the owner of the subregion, on behalf of the owner of the container. This results in a circular reference if the subregion and container have the same owner. memory_region_ref() creates a reference to the owner instead of the memory region to match the lifetime of the owner and memory region. We do not need such a hack if the subregion and container have the same owner because the owner will be alive as long as the container is. Therefore, create a reference to the subregion itself instead ot its owner in such a case; the reference to the subregion is still necessary to ensure that the subregion gets finalized after the container. Signed-off-by: Akihiko Odaki Reviewed-by: Peter Xu --- system/memory.c | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-) diff --git a/system/memory.c b/system/memory.c index 78e17e0efa83..972617b0192d 100644 --- a/system/memory.c +++ b/system/memory.c @@ -1855,6 +1855,24 @@ void memory_region_unref(MemoryRegion *mr) } } +static void memory_region_ref_subregion(MemoryRegion *subregion) +{ + if (subregion->container->owner == subregion->owner) { + object_ref(OBJECT(subregion)); + } else { + memory_region_ref(subregion); + } +} + +static void memory_region_unref_subregion(MemoryRegion *subregion) +{ + if (subregion->container->owner == subregion->owner) { + object_unref(OBJECT(subregion)); + } else { + memory_region_unref(subregion); + } +} + uint64_t memory_region_size(MemoryRegion *mr) { if (int128_eq(mr->size, int128_2_64())) { @@ -2644,7 +2662,8 @@ static void memory_region_update_container_subregions(MemoryRegion *subregion) memory_region_transaction_begin(); - memory_region_ref(subregion); + memory_region_ref_subregion(subregion); + QTAILQ_FOREACH(other, &mr->subregions, subregions_link) { if (subregion->priority >= other->priority) { QTAILQ_INSERT_BEFORE(other, subregion, subregions_link); @@ -2702,7 +2721,8 @@ void memory_region_del_subregion(MemoryRegion *mr, assert(alias->mapped_via_alias >= 0); } QTAILQ_REMOVE(&mr->subregions, subregion, subregions_link); - memory_region_unref(subregion); + memory_region_unref_subregion(subregion); + memory_region_update_pending |= mr->enabled && subregion->enabled; memory_region_transaction_commit(); }