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.
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.
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
