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[70.30.145.63]) by smtp.gmail.com with ESMTPSA id t8-20020ac85888000000b003bb8c60cdf1sm1558142qta.78.2023.02.25.08.31.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 25 Feb 2023 08:31:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1677342712; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ZVbXKBk+5YoJXuxsPRNLuFZCQaYMraNe+LiCnLIuD5I=; b=PAbAfw+zo6o64/h+EvsqlALLgeQcZktmPf+U2MJ3mwKqRGaMHwHqubYT9DUm85mgETkZ2D Zpk3QRL1FrUQbjYJzZHxm+XZsO0jhBj6IQkAJxRaCYjeSFqJ7jPvX2SWT+1ykvy8uigpUF OdmjhhLxMnZYbOW9Gc+lhHqEEoZ/1r8= X-MC-Unique: 0pzsIGMXOfSNCEuv-HPS3w-1 X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1677342707; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=ZVbXKBk+5YoJXuxsPRNLuFZCQaYMraNe+LiCnLIuD5I=; b=vxF0HeSCFtzZiRlZ93ffiWT0FlCAvA5rrhDKjlHTweSfRN18ehVid73jma0rTxv2O/ JtlPwhJxF2Pnv+xD0mjWaPfOLuHp9ZdXmuGcwOf8zBDJt0ut73vMVICaYCTdZAO2pnhM oO9TOZAFyds5GK33qih8PKMoziet8AKQ/aTyjMCLTnEKy/fj+pV5ojREkhNTLnbp63tH 3ff/7Vg9EcVzVz901cErxaDgpgOlHe0b3XU4npf7q2rrgD/aHV9G3yCwKy+yYxTOyi7N Sx5kTPmTYwYE2d3CQKbQ6x9HVqdfutwkKg0tc9wtsAd0Iw1T0f/d0FUlN/PPTdsomsM6 EPVw== X-Gm-Message-State: AO0yUKVyPstY+BntrOP72b37IbAuYwiKu+EcroCPLaknp31mNuVYfFjz kbFFlPs6pccb8u3rqPG2x3ddqG9YqXHEkzqqbeJDqOQJ3IXWTsKoICDVqz+0Ru9mwv8C48Byd0G Tj9AlqD+djMnrJRYqI+FpRV2KarJ19bLqfsBC+n8RQzV35/5q9IaKtPGuN5TqMCiMUmaprA== X-Received: by 2002:ac8:5995:0:b0:3bd:1c0f:74f3 with SMTP id e21-20020ac85995000000b003bd1c0f74f3mr37663025qte.2.1677342707412; Sat, 25 Feb 2023 08:31:47 -0800 (PST) X-Google-Smtp-Source: AK7set9hJZ6h0JepQGiVNijPwhwXgorVfOEVrqze3rqEYiDmpFG2Azp5t7kSO8f3fPFnKOEjDubc+g== X-Received: by 2002:ac8:5995:0:b0:3bd:1c0f:74f3 with SMTP id e21-20020ac85995000000b003bd1c0f74f3mr37662956qte.2.1677342706927; Sat, 25 Feb 2023 08:31:46 -0800 (PST) From: Peter Xu To: qemu-devel@nongnu.org Cc: Maxim Levitsky , Stefan Hajnoczi , Juan Quintela , Paolo Bonzini , David Hildenbrand , "Dr . David Alan Gilbert" , Chuang Xu , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , peterx@redhat.com Subject: [PATCH RFC 1/4] memory: Make memory_listeners RCU-safe for real Date: Sat, 25 Feb 2023 11:31:38 -0500 Message-Id: <20230225163141.1209368-2-peterx@redhat.com> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230225163141.1209368-1-peterx@redhat.com> References: <20230225163141.1209368-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1677342757199100009 Content-Type: text/plain; charset="utf-8" I think the plan was making memory_listeners rcu-safe, but maybe not really. This patch does it for real, by using RCU variances of qtailq helpers when modifying memory_listeners. The modification should be serialized by BQL, add assertions to register/unregister functions. Wait for a quiecent period before returning from unregister of memory listener to make sure any rcu reader is accessing valid listeners. AddressSpace.listeners are protected in the same way, so do the same. Signed-off-by: Peter Xu --- softmmu/memory.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/softmmu/memory.c b/softmmu/memory.c index 9d64efca26..a63e0bcbb7 100644 --- a/softmmu/memory.c +++ b/softmmu/memory.c @@ -3016,30 +3016,32 @@ void memory_listener_register(MemoryListener *liste= ner, AddressSpace *as) =20 /* Only one of them can be defined for a listener */ assert(!(listener->log_sync && listener->log_sync_global)); + /* Ownership of memory_listeners & as->listeners for modifications */ + assert(qemu_mutex_iothread_locked()); =20 listener->address_space =3D as; if (QTAILQ_EMPTY(&memory_listeners) || listener->priority >=3D QTAILQ_LAST(&memory_listeners)->priorit= y) { - QTAILQ_INSERT_TAIL(&memory_listeners, listener, link); + QTAILQ_INSERT_TAIL_RCU(&memory_listeners, listener, link); } else { QTAILQ_FOREACH(other, &memory_listeners, link) { if (listener->priority < other->priority) { break; } } - QTAILQ_INSERT_BEFORE(other, listener, link); + QTAILQ_INSERT_BEFORE_RCU(other, listener, link); } =20 if (QTAILQ_EMPTY(&as->listeners) || listener->priority >=3D QTAILQ_LAST(&as->listeners)->priority) { - QTAILQ_INSERT_TAIL(&as->listeners, listener, link_as); + QTAILQ_INSERT_TAIL_RCU(&as->listeners, listener, link_as); } else { QTAILQ_FOREACH(other, &as->listeners, link_as) { if (listener->priority < other->priority) { break; } } - QTAILQ_INSERT_BEFORE(other, listener, link_as); + QTAILQ_INSERT_BEFORE_RCU(other, listener, link_as); } =20 listener_add_address_space(listener, as); @@ -3051,9 +3053,14 @@ void memory_listener_unregister(MemoryListener *list= ener) return; } =20 + /* Ownership of memory_listeners & as->listeners for modifications */ + assert(qemu_mutex_iothread_locked()); + listener_del_address_space(listener, listener->address_space); - QTAILQ_REMOVE(&memory_listeners, listener, link); - QTAILQ_REMOVE(&listener->address_space->listeners, listener, link_as); + QTAILQ_REMOVE_RCU(&memory_listeners, listener, link); + QTAILQ_REMOVE_RCU(&listener->address_space->listeners, listener, link_= as); + /* Wait for RCU readers to finish. NOTE! this may release BQL */ + drain_call_rcu(); listener->address_space =3D NULL; } =20 --=20 2.39.1 From nobody Fri May 10 03:06:52 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1677342755; cv=none; d=zohomail.com; s=zohoarc; b=d+x1DDosbgFmW0l09DQSoXn8oXGmRO4p4OeWuwV74gvY7qQmfynooAh+I+oANa9b2KgLarkG+qMbYJ217cYsCLj3zUB63WdLX2rzSEgyI3EfcRz06FyASZcm03zxbtZi7TLw7Y5leVVVgl6GzR/vzdvR6rCPq2WrImJVtmB5cVo= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1677342755; h=Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=PXvHcGHMrV8Q2tJ9gSCW5uYa04vLjGWzQ6ZoHYh7V+c=; b=GzYMGG/AbEzQVtfVW+zgwBSqsxUiNJ+t7Qoh5FwLzybq76Lf9KvJTtJ5vviz7W1h6MdMZFftrXr8kjnmmHt55uf+YddAZFl78RvgXmPZEQ2VsYGU/g2elrgdTZZrhE+Mvh+Wdo94wRXHYhAYKVqrJgWW/PEC8MYq7W258U4GEQk= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=none dis=none) Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1677342755723361.08931515594566; Sat, 25 Feb 2023 08:32:35 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pVxSt-0006wV-0a; Sat, 25 Feb 2023 11:32:03 -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 1pVxSq-0006uG-ER for qemu-devel@nongnu.org; Sat, 25 Feb 2023 11:32:01 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pVxSo-0007mb-Fg for qemu-devel@nongnu.org; Sat, 25 Feb 2023 11:32:00 -0500 Received: from mail-qv1-f71.google.com (mail-qv1-f71.google.com [209.85.219.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-607-4nzEZmT8P1yykUF5FnqPyw-1; Sat, 25 Feb 2023 11:31:54 -0500 Received: by mail-qv1-f71.google.com with SMTP id pv11-20020ad4548b000000b0056e96f4fd64so1020711qvb.15 for ; Sat, 25 Feb 2023 08:31:54 -0800 (PST) Received: from x1n.redhat.com (bras-base-aurron9127w-grc-56-70-30-145-63.dsl.bell.ca. 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David Alan Gilbert" , Chuang Xu , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , peterx@redhat.com Subject: [PATCH RFC 2/4] memory: Use rcu list variance for address_spaces modifications Date: Sat, 25 Feb 2023 11:31:39 -0500 Message-Id: <20230225163141.1209368-3-peterx@redhat.com> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230225163141.1209368-1-peterx@redhat.com> References: <20230225163141.1209368-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1677342757197100007 Content-Type: text/plain; charset="utf-8" AddressSpace should be safe to RCU since it's released with call_rcu. Change the list insert/removal to use RCU variances. Signed-off-by: Peter Xu --- softmmu/memory.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/softmmu/memory.c b/softmmu/memory.c index a63e0bcbb7..c48e9cc6ed 100644 --- a/softmmu/memory.c +++ b/softmmu/memory.c @@ -3079,7 +3079,7 @@ void address_space_init(AddressSpace *as, MemoryRegio= n *root, const char *name) as->ioeventfd_nb =3D 0; as->ioeventfds =3D NULL; QTAILQ_INIT(&as->listeners); - QTAILQ_INSERT_TAIL(&address_spaces, as, address_spaces_link); + QTAILQ_INSERT_TAIL_RCU(&address_spaces, as, address_spaces_link); as->name =3D g_strdup(name ? name : "anonymous"); address_space_update_topology(as); address_space_update_ioeventfds(as); @@ -3103,7 +3103,7 @@ void address_space_destroy(AddressSpace *as) memory_region_transaction_begin(); as->root =3D NULL; memory_region_transaction_commit(); - QTAILQ_REMOVE(&address_spaces, as, address_spaces_link); + QTAILQ_REMOVE_RCU(&address_spaces, as, address_spaces_link); =20 /* At this point, as->dispatch and as->current_map are dummy * entries that the guest should never use. 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David Alan Gilbert" , Chuang Xu , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , peterx@redhat.com Subject: [PATCH RFC 3/4] memory: Protect memory_region_clear_dirty_bitmap with RCU Date: Sat, 25 Feb 2023 11:31:40 -0500 Message-Id: <20230225163141.1209368-4-peterx@redhat.com> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230225163141.1209368-1-peterx@redhat.com> References: <20230225163141.1209368-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1677342797051100001 Content-Type: text/plain; charset="utf-8" Clear dirty bitmap operation needs to walk memory_listeners but the context may not hold BQL. These callers hold BQL for it: cpu_physical_memory_sync_dirty_bitmap dirtyrate_manual_reset_protect These callers hold RCU for it: migration_clear_memory_region_dirty_bitmap [1] cpu_physical_memory_test_and_clear_dirty The above case [1] is extremely unobvious and probably still buggy, because: - Either the RCU read lock was taken very high from the stack in ram_save_iterate() or ram_save_queue_pages() where the RCU lock was probably taken for the sake of ramblock references (which is also protected by RCU), or, - I _think_ there's path that leaks taking any lock (e.g. the other path migration_clear_memory_region_dirty_bitmap_range which is used by virtio-mem or virtio-balloon that may or may not really take RCU at all, neither BQL). Add the RCU read lock in memory_region_clear_dirty_bitmap() to make sure it's not missed. The RCU is also needed for address_space_get_flatview(), so this will generally making the RCU section larger to cover the whole walking process when not taken, but wanted. This should be the only place that we referenced memory_listeners (or as->listeners) without guaranteed to hold BQL nor RCU. Signed-off-by: Peter Xu --- softmmu/memory.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/softmmu/memory.c b/softmmu/memory.c index c48e9cc6ed..95cdcaeccf 100644 --- a/softmmu/memory.c +++ b/softmmu/memory.c @@ -2270,7 +2270,8 @@ void memory_region_clear_dirty_bitmap(MemoryRegion *m= r, hwaddr start, FlatRange *fr; hwaddr sec_start, sec_end, sec_size; =20 - QTAILQ_FOREACH(listener, &memory_listeners, link) { + RCU_READ_LOCK_GUARD(); + QTAILQ_FOREACH_RCU(listener, &memory_listeners, link) { if (!listener->log_clear) { continue; } --=20 2.39.1 From nobody Fri May 10 03:06:52 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1677342754; cv=none; d=zohomail.com; s=zohoarc; b=nR4rKs9E78btCtvCKtBQqV9wT4AmK1M5o9e27ART/vjAfRyodnEygR/w6fon3+T7JkmgffMkwByQ3Guvh7JOYkE7PZW+kBYEbfcyiOZjvBgb1PiiRa3R34WwJziwp2fvzS/x8VfnjsSwwOQHv6XTTv1jioMBAm3SL+KHb2aHlQs= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1677342754; h=Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=3nMIHYNGqj7vLSxK7AMfLxIZi6naTf38R3aAeG349Ag=; b=IBPnIVArLFkCTEl/hKbAlTUYfV6CDR1icY1Q8Gn+W9shgo/0Kl5E98mpprGS0QN4ubyPQknGF5wsTBlZXDceHfYW2Wiif6PVwMuG/1eMtB3Kyzb9gIT6P+v6nWdsQD3AdQqDZF6UnTsDhngGDoN/iyCWQPMIjmtpbKR8xs6LBwQ= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=none dis=none) Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1677342754907905.7351793367037; Sat, 25 Feb 2023 08:32:34 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pVxT0-0006xx-3X; Sat, 25 Feb 2023 11:32:10 -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 1pVxSt-0006wq-K0 for qemu-devel@nongnu.org; Sat, 25 Feb 2023 11:32:03 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pVxSs-0007pL-3N for qemu-devel@nongnu.org; Sat, 25 Feb 2023 11:32:03 -0500 Received: from mail-qt1-f199.google.com (mail-qt1-f199.google.com [209.85.160.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-645-4QOT8huHP5urebqR2WVUMg-1; Sat, 25 Feb 2023 11:31:59 -0500 Received: by mail-qt1-f199.google.com with SMTP id k19-20020ac86053000000b003bd0d4e3a50so1297431qtm.9 for ; Sat, 25 Feb 2023 08:31:59 -0800 (PST) Received: from x1n.redhat.com (bras-base-aurron9127w-grc-56-70-30-145-63.dsl.bell.ca. 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David Alan Gilbert" , Chuang Xu , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , peterx@redhat.com Subject: [PATCH RFC 4/4] memory: Use rcu traversal in memory_region_to_address_space Date: Sat, 25 Feb 2023 11:31:41 -0500 Message-Id: <20230225163141.1209368-5-peterx@redhat.com> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230225163141.1209368-1-peterx@redhat.com> References: <20230225163141.1209368-1-peterx@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1677342757006100003 Content-Type: text/plain; charset="utf-8" memory_region_to_address_space() is the only function that walks the address_spaces list using RCU read lock only. Use the RCU walker to reflect that. Signed-off-by: Peter Xu --- softmmu/memory.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/softmmu/memory.c b/softmmu/memory.c index 95cdcaeccf..0b652d9597 100644 --- a/softmmu/memory.c +++ b/softmmu/memory.c @@ -566,7 +566,7 @@ static AddressSpace *memory_region_to_address_space(Mem= oryRegion *mr) while (mr->container) { mr =3D mr->container; } - QTAILQ_FOREACH(as, &address_spaces, address_spaces_link) { + QTAILQ_FOREACH_RCU(as, &address_spaces, address_spaces_link) { if (mr =3D=3D as->root) { return as; } --=20 2.39.1