On Mon, May 18, 2020 at 10:50:39AM +0800, Jason Wang wrote: > > On 2020/5/16 上午12:54, 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? > > > I think I agree with Michael, it's better to have a generic vhost-user > solution. But if it turns out to be not easy, we can start from fixing > vhost-user-blk. I also agree, but as i see it right now the connect/disconnect events are handled inside each vhost-user device implementation file. So it will need some global refactoring. So i suggest having this fix first and after it refactoring the code: - more devices will be involved - i see there is some difference in device handling
> > > >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 <ram_state>) > > at ./migration/ram.c:2323 > > #6 0x00005648ea2e6cc5 in ram_save_setup (f=0x5648ec609e00, > > opaque=0x5648eb1f0f20 <ram_state>) > > 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? > > > This requires more thought, I will reply in Feng's mail. Okay, let's continue discussion there. No other comments mixed in below. Thanks, Dima. > > Thanks > > > > > >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 > >>> >