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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6c75e494a28sm30486d6.68.2024.09.18.11.32.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Sep 2024 11:32:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1726684328; 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=wcORaTdOlKE0GN8MprplNyrFUTHIsXM5RvJ3/UsElD0=; b=fVC5PCWMc7js8wj6Qhfpf7xCRSuNVotVrdJCd+fCl8/CXgagkLRiydnGU3c9l2G0B0VYQV gBUQb+W4PZkaqfCFY+zKHWH4VR7rRYkjijy7+uHeEudk64fHmRi/d1bN+Vukd4fPj+SBgH sP2ERPkfCDaLVO6buv+hjcFTaM35R2g= X-MC-Unique: SbdMavxVNFWNVKZRe1qzUQ-1 X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1726684326; x=1727289126; 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=wcORaTdOlKE0GN8MprplNyrFUTHIsXM5RvJ3/UsElD0=; b=no2rMXAP7Tmz9M1sSJe0ytiLLbA7HEpe+a0l6EsJ/2m+DahDZAGoymdWCRnRIBL0hT aOX3ju9dZrgRG6rGZoj0gME4goYyxFlKo/vAJPIe5V2M1MBQNyqmW4bJkSQMEo7KeGQn ltr39HonlDF4M/loqAx6xyMKPZfar5Tby0aAA8GsjvN4t64pd5lkkEzV4Mpg9MALUbD2 Jf3q7Tzi8FK18/3oTdefAnjSaUcd1lx93pD2utgfqubv9LlyAaVgIvkZDeuBnRNRCslF TegTnNyvIgHVQNykGn1gTT2IJctRs3GDIk915Gi/+vGC5cEljlp4Vs8R6wv2qqVyGBck PqKQ== X-Gm-Message-State: AOJu0YxSDNJxNpDzK7P+CabtgxpF/VudCUX3INrcjwR8YyyprXWUP6aM 4IxipK3p7zblelCzi8EkvjGJT9joG6ITIhIm9ZzClMXJH2o69PA9iGTJJ+ttijUF6ioMKr5l8U0 BrKbEAZdkHU+ShUIH3g0QKNm1sZWZGrOzN649wFVnfrhrk6zonH4wXWrvqHVj8WDaoRaxE5tX3/ CDPn0Hyy7ecbv1Q1rofRVd61BHTFTPeN2QnA== X-Received: by 2002:a05:6214:45a1:b0:6c3:5d09:cf8a with SMTP id 6a1803df08f44-6c5735685cemr388022686d6.26.1726684325727; Wed, 18 Sep 2024 11:32:05 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGXFYWKFgiIiQNDUCgj/GfFeJlifIaFPAalwWfksM3aEif90jC2SVvLMS0Lz9rbi/QuHgkd1Q== X-Received: by 2002:a05:6214:45a1:b0:6c3:5d09:cf8a with SMTP id 6a1803df08f44-6c5735685cemr388022266d6.26.1726684325316; Wed, 18 Sep 2024 11:32:05 -0700 (PDT) From: Peter Xu To: qemu-devel@nongnu.org Cc: Paolo Bonzini , David Hildenbrand , Peter Maydell , Fabiano Rosas , peterx@redhat.com, qemu-stable@nongnu.org Subject: [PULL v2 6/6] migration/multifd: Fix rb->receivedmap cleanup race Date: Wed, 18 Sep 2024 14:31:51 -0400 Message-ID: <20240918183151.6413-7-peterx@redhat.com> X-Mailer: git-send-email 2.45.0 In-Reply-To: <20240918183151.6413-1-peterx@redhat.com> References: <20240918183151.6413-1-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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=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: 1726684420905116600 Content-Type: text/plain; charset="utf-8" From: Fabiano Rosas Fix a segmentation fault in multifd when rb->receivedmap is cleared too early. After commit 5ef7e26bdb ("migration/multifd: solve zero page causing multiple page faults"), multifd started using the rb->receivedmap bitmap, which belongs to ram.c and is initialized and *freed* from the ram SaveVMHandlers. Multifd threads are live until migration_incoming_state_destroy(), which is called after qemu_loadvm_state_cleanup(), leading to a crash when accessing rb->receivedmap. process_incoming_migration_co() ... qemu_loadvm_state() multifd_nocomp_recv() qemu_loadvm_state_cleanup() ramblock_recv_bitmap_set_offset() rb->receivedmap =3D NULL set_bit_atomic(..., rb->receiv= edmap) ... migration_incoming_state_destroy() multifd_recv_cleanup() multifd_recv_terminate_threads(NULL) Move the loadvm cleanup into migration_incoming_state_destroy(), after multifd_recv_cleanup() to ensure multifd threads have already exited when rb->receivedmap is cleared. Adjust the postcopy listen thread comment to indicate that we still want to skip the cpu synchronization. CC: qemu-stable@nongnu.org Fixes: 5ef7e26bdb ("migration/multifd: solve zero page causing multiple pag= e faults") Signed-off-by: Fabiano Rosas Link: https://lore.kernel.org/r/20240917185802.15619-3-farosas@suse.de [peterx: added comment in migration_incoming_state_destroy()] Signed-off-by: Peter Xu --- migration/migration.c | 5 +++++ migration/savevm.c | 6 ++++-- 2 files changed, 9 insertions(+), 2 deletions(-) diff --git a/migration/migration.c b/migration/migration.c index 3dea06d577..ae2be31557 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -378,6 +378,11 @@ void migration_incoming_state_destroy(void) struct MigrationIncomingState *mis =3D migration_incoming_get_current(= ); =20 multifd_recv_cleanup(); + /* + * RAM state cleanup needs to happen after multifd cleanup, because + * multifd threads can use some of its states (receivedmap). + */ + qemu_loadvm_state_cleanup(); =20 if (mis->to_src_file) { /* Tell source that we are done */ diff --git a/migration/savevm.c b/migration/savevm.c index d0759694fd..7e1e27182a 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -2979,7 +2979,10 @@ int qemu_loadvm_state(QEMUFile *f) trace_qemu_loadvm_state_post_main(ret); =20 if (mis->have_listen_thread) { - /* Listen thread still going, can't clean up yet */ + /* + * Postcopy listen thread still going, don't synchronize the + * cpus yet. + */ return ret; } =20 @@ -3022,7 +3025,6 @@ int qemu_loadvm_state(QEMUFile *f) } } =20 - qemu_loadvm_state_cleanup(); cpu_synchronize_all_post_init(); =20 return ret; --=20 2.45.0