On 15.12.22 06:22, Viresh Kumar wrote:
Hello Viresh
On 14-12-22, 17:01, Oleksandr Tyshchenko wrote:
Today I had a chance to check virtio-disk on my H/W using new Xen branch
which does include Juergen's series with commit 3a96013a3e17
("tools/xenstore: reduce number of watch events").
Very interesting, but I didn't manage to reproduce an issue the similar to
what you had already faced with the rust counterparts before (caused by the
lack of Xenstore watches?). Note that I didn't debug what exactly events I
had got during guest creation/destruction, I just made sure that backend
worked as before. I checked that by running the backend in Dom0 and DomD and
performed a couple of guest power cycles (reboot, destroy/create).
If you could provide the debug patch which you seem to use to print incoming
events which you described in previous email, I think I would be able to
re-check the situation at my side more deeper.
This should be enough to see the new changes I believe.
diff --git a/xs_dev.c b/xs_dev.c
index a6c8403cfe84..8525c6512299 100755
--- a/xs_dev.c
+++ b/xs_dev.c
@@ -421,6 +421,8 @@ static int xenstore_poll_be_watch(struct xs_dev *dev)
if (!vec)
return -1;
+ printf("%s: %s\n", vec[XS_WATCH_PATH], dev->path);
+
if (!strcmp(vec[XS_WATCH_PATH], dev->path))
rc = xenstore_get_fe_domid(dev);
Thanks. This print does not provide much information in my case
(virtio-disk). All what I see here in both cases (with old and new Xen)
during guest creation is the following:
"backend/virtio_disk: backend/virtio_disk"
But, if I modify the xenstore_get_fe_domid() to always return 0 and as
the result to get stuck here, I can see subsequent events for other
paths here.
I agree that with new Xen (after commit 3a96013a3e17 "tools/xenstore:
reduce number of watch events"), some events are missing now, but I
still don't see an issue with virtio-disk and can't see why it is going
to be an issue. The code doesn't wait for the last "finalizing" event
for the root directory "backend/virtio_disk", it goes ahead to find the
FE domid right after receiving the first event.
new Xen:
oot@generic-armv8-xt-dom0:~# xl console DomD
backend/virtio_disk/6/51713: backend/virtio_disk
backend/virtio_disk/6/51713/frontend: backend/virtio_disk
backend/virtio_disk/6/51713/params: backend/virtio_disk
backend/virtio_disk/6/51713/frontend-id: backend/virtio_disk
backend/virtio_disk/6/51713/online: backend/virtio_disk
backend/virtio_disk/6/51713/removable: backend/virtio_disk
backend/virtio_disk/6/51713/bootable: backend/virtio_disk
backend/virtio_disk/6/51713/state: backend/virtio_disk
backend/virtio_disk/6/51713/dev: backend/virtio_disk
backend/virtio_disk/6/51713/type: backend/virtio_disk
backend/virtio_disk/6/51713/mode: backend/virtio_disk
backend/virtio_disk/6/51713/device-type: backend/virtio_disk
backend/virtio_disk/6/51713/discard-enable: backend/virtio_disk
backend/virtio_disk/6/51713/specification: backend/virtio_disk
backend/virtio_disk/6/51713/transport: backend/virtio_disk
backend/virtio_disk/6/51713/base: backend/virtio_disk
backend/virtio_disk/6/51713/irq: backend/virtio_disk
old Xen:
root@generic-armv8-xt-dom0:~# xl console DomD
backend/virtio_disk/4/51713: backend/virtio_disk
backend/virtio_disk/4: backend/virtio_disk
backend/virtio_disk: backend/virtio_disk
backend/virtio_disk/4/51713/frontend: backend/virtio_disk
backend/virtio_disk/4/51713/params: backend/virtio_disk
backend/virtio_disk/4/51713/frontend-id: backend/virtio_disk
backend/virtio_disk/4/51713/online: backend/virtio_disk
backend/virtio_disk/4/51713/removable: backend/virtio_disk
backend/virtio_disk/4/51713/bootable: backend/virtio_disk
backend/virtio_disk/4/51713/state: backend/virtio_disk
backend/virtio_disk/4/51713/dev: backend/virtio_disk
backend/virtio_disk/4/51713/type: backend/virtio_disk
backend/virtio_disk/4/51713/mode: backend/virtio_disk
backend/virtio_disk/4/51713/device-type: backend/virtio_disk
backend/virtio_disk/4/51713/discard-enable: backend/virtio_disk
backend/virtio_disk/4/51713/specification: backend/virtio_disk
backend/virtio_disk/4/51713/transport: backend/virtio_disk
backend/virtio_disk/4/51713/base: backend/virtio_disk
backend/virtio_disk/4/51713/irq: backend/virtio_disk
At the same time the code to automatically determine the FE domid is not
ideal, for the instance, it is based on the assumption
that new FE domid should be always greater than old FE domid (which as I
understand *might* be wrong) and contains a delay, so wants to be improved.
