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[62.83.194.64]) by smtp.gmail.com with ESMTPSA id a9sm20699251wrv.37.2021.06.30.02.13.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Jun 2021 02:13:56 -0700 (PDT) From: Juan Quintela To: Laurent Vivier Subject: Re: [PATCH 2/2] migration: failover: continue to wait card unplug on error In-Reply-To: (Laurent Vivier's message of "Wed, 30 Jun 2021 11:04:38 +0200") References: <20210629155007.629086-1-lvivier@redhat.com> <20210629155007.629086-3-lvivier@redhat.com> <87im1wk1ap.fsf@secure.mitica> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) Date: Wed, 30 Jun 2021 11:13:55 +0200 Message-ID: <871r8jzpd8.fsf@secure.mitica> MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=quintela@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=216.205.24.124; envelope-from=quintela@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.435, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: quintela@redhat.com Cc: Jens Freimann , qemu-devel@nongnu.org, "Dr. David Alan Gilbert" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Laurent Vivier wrote: > On 29/06/2021 19:50, Juan Quintela wrote: >> Laurent Vivier wrote: >>> If the user cancels the migration in the unplug-wait state, >>> QEMU will try to plug back the card and this fails because the card >>> is partially unplugged. >>> To avoid the problem, continue to wait the card unplug, but to >>> allow the migration to be canceled if the card never finishes to unplug >>> use a timeout. >>> >>> Bug: https://bugzilla.redhat.com/show_bug.cgi?id=1976852 >>> Signed-off-by: Laurent Vivier >>> --- >>> migration/migration.c | 11 +++++++++++ >>> 1 file changed, 11 insertions(+) >>> >>> diff --git a/migration/migration.c b/migration/migration.c >>> index 3e92c405a2b6..3b06d43a7f42 100644 >>> --- a/migration/migration.c >>> +++ b/migration/migration.c >>> @@ -3679,6 +3679,17 @@ static void qemu_savevm_wait_unplug(MigrationState *s, int old_state, >>> qemu_savevm_state_guest_unplug_pending()) { >>> qemu_sem_timedwait(&s->wait_unplug_sem, 250); >>> } >>> + if (s->state != MIGRATION_STATUS_WAIT_UNPLUG) { >>> + int timeout = 120; /* 30 seconds */ >>> + /* >>> + * migration has been canceled >>> + * but as we have started an unplug we must wait the end >>> + * to be able to plug back the card >>> + */ >>> + while (timeout-- && qemu_savevm_state_guest_unplug_pending()) { >>> + qemu_sem_timedwait(&s->wait_unplug_sem, 250); >>> + } >>> + } >>> >>> migrate_set_state(&s->state, MIGRATION_STATUS_WAIT_UNPLUG, new_state); >>> } else { >> I agree with the idea. But if we are getting out due to timeout == 0, >> shouldn't we return some error, warning, whatever? > > In that case, we keep the current behaviour: guest kernel will report > an error when it > will try to plug back the card that has not been unplugged. This is a > corner case: if it > happens we have something really wrong with the machine. Perhaps we can remove the > timeout, but I don't like to block the user, or increase it to be sure. Oh, I whole agree that it is a corner case, and that it shouldn't happen. But if it happens, we don't log it anywhere. That was my complaint. Later, Juan.