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[109.66.118.94]) by smtp.gmail.com with ESMTPSA id g24sm21220283wrb.35.2020.05.19.02.59.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 May 2020 02:59:10 -0700 (PDT) Date: Tue, 19 May 2020 05:59:07 -0400 From: "Michael S. Tsirkin" To: Dima Stepanov Subject: Re: [PATCH v2 5/5] vhost: add device started check in migration set log Message-ID: <20200517101303-mutt-send-email-mst@kernel.org> References: <20200511092541.GA27558@dimastep-nix> <20200512093521.GA5363@dimastep-nix> <20200512235934-mutt-send-email-mst@kernel.org> <20200513094703.GA15906@dimastep-nix> <722839b2-9412-b768-3ce6-d1b697d6d5dd@redhat.com> <20200515165449.GA1627@dimastep-nix> MIME-Version: 1.0 In-Reply-To: <20200515165449.GA1627@dimastep-nix> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Disposition: inline Received-SPF: pass client-ip=205.139.110.120; envelope-from=mst@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/18 23:56:10 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN 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: , Cc: fam@euphon.net, kwolf@redhat.com, yc-core@yandex-team.ru, qemu-block@nongnu.org, Jason Wang , qemu-devel@nongnu.org, dgilbert@redhat.com, arei.gonglei@huawei.com, fengli@smartx.com, stefanha@redhat.com, marcandre.lureau@redhat.com, pbonzini@redhat.com, raphael.norwitz@nutanix.com, mreitz@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, May 15, 2020 at 07:54:57PM +0300, Dima Stepanov wrote: > On Thu, May 14, 2020 at 03:34:24PM +0800, Jason Wang wrote: > > > > On 2020/5/13 下午5:47, Dima Stepanov wrote: > > >>> case CHR_EVENT_CLOSED: > > >>> /* a close event may happen during a read/write, but vhost > > >>> * code assumes the vhost_dev remains setup, so delay the > > >>> * stop & clear to idle. > > >>> * FIXME: better handle failure in vhost code, remove bh > > >>> */ > > >>> if (s->watch) { > > >>> AioContext *ctx = qemu_get_current_aio_context(); > > >>> > > >>> g_source_remove(s->watch); > > >>> s->watch = 0; > > >>> qemu_chr_fe_set_handlers(&s->chr, NULL, NULL, NULL, NULL, > > >>> NULL, NULL, false); > > >>> > > >>> aio_bh_schedule_oneshot(ctx, chr_closed_bh, opaque); > > >>> } > > >>> break; > > >>> > > >>>I think it's time we dropped the FIXME and moved the handling to common > > >>>code. Jason? Marc-André? > > >>I agree. Just to confirm, do you prefer bh or doing changes like what is > > >>done in this series? It looks to me bh can have more easier codes. > > >Could it be a good idea just to make disconnect in the char device but > > >postphone clean up in the vhost-user-blk (or any other vhost-user > > >device) itself? So we are moving the postphone logic and decision from > > >the char device to vhost-user device. One of the idea i have is as > > >follows: > > > - Put ourself in the INITIALIZATION state > > > - Start these vhost-user "handshake" commands > > > - If we got a disconnect error, perform disconnect, but don't clean up > > > device (it will be clean up on the roll back). I can be done by > > > checking the state in vhost_user_..._disconnect routine or smth like it > > > > > > Any issue you saw just using the aio bh as Michael posted above. > > > > Then we don't need to deal with the silent vhost_dev_stop() and we will have > > codes that is much more easier to understand. > I've implemented this solution inside > hw/block/vhost-user-blk.c:vhost_user_blk_event() in the similar way by > using the s->connected field. Looks good and more correct fix ). I have > two questions here before i'll rework the fixes: > 1. Is it okay to make the similar fix inside vhost_user_blk_event() or > we are looking for more generic vhost-user solution? What do you think? Either works I think. > 2. For migration we require an additional information that for the > vhost-user device it isn't an error, because i'm trigerring the > following assert error: > Core was generated by `x86_64-softmmu/qemu-system-x86_64 -nodefaults -no-user-config -M q35,sata=false'. > Program terminated with signal SIGABRT, Aborted. > #0 0x00007fb56e729428 in raise () from /lib/x86_64-linux-gnu/libc.so.6 > [Current thread is 1 (Thread 0x7fb486ef5700 (LWP 527734))] > > (gdb) bt > #0 0x00007fb56e729428 in raise () from /lib/x86_64-linux-gnu/libc.so.6 > #1 0x00007fb56e72b02a in abort () from /lib/x86_64-linux-gnu/libc.so.6 > #2 0x00005648ea376ee6 in vhost_log_global_start > (listener=0x5648ece4eb08) at ./hw/virtio/vhost.c:857 > #3 0x00005648ea2dde7e in memory_global_dirty_log_start () > at ./memory.c:2611 > #4 0x00005648ea2e68e7 in ram_init_bitmaps (rs=0x7fb4740008c0) > at ./migration/ram.c:2305 > #5 0x00005648ea2e698b in ram_init_all (rsp=0x5648eb1f0f20 ) > at ./migration/ram.c:2323 > #6 0x00005648ea2e6cc5 in ram_save_setup (f=0x5648ec609e00, > opaque=0x5648eb1f0f20 ) > at ./migration/ram.c:2436 > #7 0x00005648ea67b7d3 in qemu_savevm_state_setup (f=0x5648ec609e00) at > migration/savevm.c:1176 > #8 0x00005648ea674511 in migration_thread (opaque=0x5648ec031ff0) at > migration/migration.c:3416 > #9 0x00005648ea85d65d in qemu_thread_start (args=0x5648ec6057f0) at > util/qemu-thread-posix.c:519 > #10 0x00007fb56eac56ba in start_thread () from > /lib/x86_64-linux-gnu/libpthread.so.0 > #11 0x00007fb56e7fb41d in clone () from /lib/x86_64-linux-gnu/libc.so.6 > (gdb) frame 2 > #2 0x00005648ea376ee6 in vhost_log_global_start > (listener=0x5648ece4eb08) at ./hw/virtio/vhost.c:857 > 857 abort(); > (gdb) list > 852 { > 853 int r; > 854 > 855 r = vhost_migration_log(listener, true); > 856 if (r < 0) { > 857 abort(); > 858 } > 859 } > 860 > 861 static void vhost_log_global_stop(MemoryListener *listener) > Since bh postphone the clean up, we can't use the ->started field. > Do we have any mechanism to get the device type/state in the common > vhost_migration_log() routine? So for example for the vhost-user/disconnect > device we will be able to return 0. Or should we implement it and introduce > it in this patch set? > > Thanks, Dima. > > > > > Thank > > > > > > > - vhost-user command returns error back to the _start() routine > > > - Rollback in one place in the start() routine, by calling this > > > postphoned clean up for the disconnect > > > > >