On Thu, Jan 25, 2018 at 03:39:55PM +0300, Klim Kireev wrote: > The following behavior was observed for QEMU configured by libvirt > to use guest agent as usual for the guests without virtio-serial > driver (Windows or the guest remaining in BIOS stage). > > In QEMU on first connect to listen character device socket > the listen socket is removed from poll just after the accept(). > virtio_serial_guest_ready() returns 0 and the descriptor > of the connected Unix socket is removed from poll and it will > not be present in poll() until the guest will initialize the driver > and change the state of the serial to "guest connected". > > In libvirt connect() to guest agent is performed on restart and > is run under VM state lock. Connect() is blocking and can > wait forever. > In this case libvirt can not perform ANY operation on that VM. > > The bug can be easily reproduced this way: > > Terminal 1: > qemu-system-x86_64 -m 512 -device pci-serial,chardev=serial1 -chardev > socket,id=serial1,path=/tmp/console.sock,server,nowait > (virtio-serial and isa-serial also fit) > > Terminal 2: > minicom -D unix\#/tmp/console.sock > (type something and press enter) > C-a x (to exit) > > Do 3 times: > minicom -D unix\#/tmp/console.sock > C-a x > > It needs 4 connections, because the first one is accepted by QEMU, then two > are queued by > the kernel, and the 4th blocks. > > The problem is that QEMU doesn't add a read watcher after succesful read > until the guest device wants to acquire recieved data, so > I propose to install a separate pullhup watcher regardless of > whether the device waits for data or not. > > Signed-off-by: Klim Kireev <klim.kir...@virtuozzo.com> > --- > Changelog: > v2: Remove timer as a redundant feature > > v3: Remove read call and return G_SOURCE_REMOVE > > v4: Move to GSource API > > chardev/char-socket.c | 22 ++++++++++++++++++++++ > dtc | 2 +- > 2 files changed, 23 insertions(+), 1 deletion(-)
> diff --git a/dtc b/dtc > index e54388015a..558cd81bdd 160000 > --- a/dtc > +++ b/dtc > @@ -1 +1 @@ > -Subproject commit e54388015af1fb4bf04d0bca99caba1074d9cc42 > +Subproject commit 558cd81bdd432769b59bff01240c44f82cfb1a9d Presumably accidental. You can fix this by doing cd dtc git checkout e54388015af1fb4bf04d0bca99caba1074d9cc42 cd .. git add dtc git commit --amend Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
