From patchwork Sat Jan 4 07:33:36 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Akihiko Odaki X-Patchwork-Id: 13926117 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 5F836E77188 for ; Sat, 4 Jan 2025 07:35:01 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tTyfj-0000oF-9H; Sat, 04 Jan 2025 02:34:11 -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 1tTyfY-0000jo-7L for qemu-devel@nongnu.org; Sat, 04 Jan 2025 02:34:03 -0500 Received: from mail-pj1-x1033.google.com ([2607:f8b0:4864:20::1033]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1tTyfW-0004YA-Qb for qemu-devel@nongnu.org; Sat, 04 Jan 2025 02:34:00 -0500 Received: by mail-pj1-x1033.google.com with SMTP id 98e67ed59e1d1-2f13acbe29bso16280143a91.1 for ; Fri, 03 Jan 2025 23:33:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=daynix-com.20230601.gappssmtp.com; s=20230601; t=1735976036; x=1736580836; 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=FmQmqRoZoVpBuUWMsWoA3ZXBC95hvdxu9mQlkpJR1U4=; b=UqnDMiIohno1vbBDtn2K4bU3aLasCoWSBAnNZEnQfsEYmN1qyJUftti7gJt57gDGry aL5CsIeOPJMVHcE9w2nHsKPqbe0hct3kAmYIYIj0N2X+W5qFnM8gmkKPOkOSUyflOig8 Svz5RU69UQ6NYfdCzbh/ucUakJX0gbyYgki/zUZOlkePn/Vd86+27c+r4l1NA8iJoTMz 4RDgnBVMwb0MJSQb9ROnUyo/oswwLMJolJk8hygqyI9OyYvIXCEmaCLuIrDaeWYgZ7iE IBr+aqouXlC0s8uKdILleMXR2IlO0x5Ah9LLEE2Mge/i+KBPFULEy1QjzDePL1Mxz3kL RFEg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1735976036; x=1736580836; 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=FmQmqRoZoVpBuUWMsWoA3ZXBC95hvdxu9mQlkpJR1U4=; b=C7Q6SbDUwnz7JbHa3GOUqKnL3MZ5JAnypq4uNLo9SZaKayMe16nP5ug84kW3+AffOO vcr5ZU2MPhgg1zkBFlPIRro4E8IXCHFUWR9PPAKBXON1ZLYx3I/6xQE076POmCmU1ihU Ek1GQvB66Y5C81d/8UiTcOUVPsoRHiuWJ4DoRLaQWL35ycUvRVwpO0upAinOOLQengZ/ i3ZFv+JFlovc8wUfvR7ybg2v2Y68D8PCA3L4RYueeFKFLLLYqO0Tmqznf0hHIuvBc0Fn FPTcpH7OK3Cr1K4WdhwEB06Uu6DoAyTdvuKur/8YImTcWAIrkgwTkDiki6pxXs5hCSZg kfoQ== X-Gm-Message-State: AOJu0YwygHatRLkUMMBIsfmTVptuDRLKBny4P+GsmR9JK1iGExk/6Dqu UixxyMcNVXoDZSaO2Q/moOSplXKIdMOHXSnG2dJjNSxvciLm2peH7SskfThBzQY= X-Gm-Gg: ASbGncsJJLJAJoFNm+WhAMm3aEwf8qBACp5ym7HfKdw/36zrOzQ9TqPY3eMF6iejnCy JiqAvMvDno3yTCqPKQ+CkYuo9helZiRytz4cx1pPWy9EdexCK9VHO0vwv3UW24iKl13TJ11+AqN Dws5efzDvo3RlHO3ONi2nhu94c1z8xjJeqnbP6GqFe7ZNW2zUUPsB19GHIG36fJdl/jIafVl3IS 8rgH80XLSdYakSOeCIqHH3XZoOhy6sigttn5B0IiOlJExQDqCOrYeA4oAdn X-Google-Smtp-Source: AGHT+IEZIbBS4o9zJftEjQUEomOOL4cxjelKHf6/Eg4YfsOwWE0OCG+7iDptMIpHY76zX+g64HZapg== X-Received: by 2002:a17:90a:c2c4:b0:2ee:463d:8e8d with SMTP id 98e67ed59e1d1-2f4437bf735mr84231699a91.14.1735976036291; Fri, 03 Jan 2025 23:33:56 -0800 (PST) Received: from localhost ([157.82.207.107]) by smtp.gmail.com with UTF8SMTPSA id 98e67ed59e1d1-2f454f58087sm30691132a91.11.2025.01.03.23.33.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 03 Jan 2025 23:33:56 -0800 (PST) From: Akihiko Odaki Date: Sat, 04 Jan 2025 16:33:36 +0900 Subject: [PATCH v5 2/2] memory: Do not create circular reference with subregion MIME-Version: 1.0 Message-Id: <20250104-san-v5-2-8b430457b09d@daynix.com> References: <20250104-san-v5-0-8b430457b09d@daynix.com> In-Reply-To: <20250104-san-v5-0-8b430457b09d@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::1033; envelope-from=akihiko.odaki@daynix.com; helo=mail-pj1-x1033.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 --- system/memory.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/system/memory.c b/system/memory.c index 78e17e0efa83..16b051249c5f 100644 --- a/system/memory.c +++ b/system/memory.c @@ -2644,7 +2644,9 @@ static void memory_region_update_container_subregions(MemoryRegion *subregion) memory_region_transaction_begin(); - memory_region_ref(subregion); + object_ref(mr->owner == subregion->owner ? + OBJECT(subregion) : subregion->owner); + QTAILQ_FOREACH(other, &mr->subregions, subregions_link) { if (subregion->priority >= other->priority) { QTAILQ_INSERT_BEFORE(other, subregion, subregions_link); @@ -2702,7 +2704,9 @@ void memory_region_del_subregion(MemoryRegion *mr, assert(alias->mapped_via_alias >= 0); } QTAILQ_REMOVE(&mr->subregions, subregion, subregions_link); - memory_region_unref(subregion); + object_unref(mr->owner == subregion->owner ? + OBJECT(subregion) : subregion->owner); + memory_region_update_pending |= mr->enabled && subregion->enabled; memory_region_transaction_commit(); }