The commit's purpose is laudable:
The only way for chardev drivers to communicate an error was to
return a NULL pointer, which resulted in an error message that
said _that_ something went wrong, but not _why_.
It attempts to achieve it by changing the interface to return 0/-errno
and update qemu_chr_open_opts() to use strerror() to display a more
helpful error message. Unfortunately, it has serious flaws:
1. Backends "socket" and "udp" return bogus error codes, because
qemu_chr_open_socket() and qemu_chr_open_udp() assume that
unix_listen_opts(), unix_connect_opts(), inet_listen_opts(),
inet_connect_opts() and inet_dgram_opts() fail with errno set
appropriately. That assumption is wrong, and the commit turns
unspecific error messages into misleading error messages. For
instance:
$ qemu-system-x86_64 -nodefaults -vnc :0 -chardev socket,id=bar,host=xxx
inet_connect: host and/or port not specified
chardev: opening backend "socket" failed: No such file or directory
ENOENT is what happens to be in my errno when the backend returns
-errno. Let's put ERANGE there just for giggles:
$ qemu-system-x86_64 -nodefaults -vnc :0 -chardev socket,id=bar,host=xxx -drive if=none,iops=99999999999999999999
inet_connect: host and/or port not specified
chardev: opening backend "socket" failed: Numerical result out of range
Worse: when errno happens to be zero, return -errno erroneously
signals success, and qemu_chr_new_from_opts() dies dereferencing
uninitialized chr. I observe this with "-serial unix:".
2. All qemu_chr_open_opts() knows about the error is an errno error
code. That's simply not enough for a decent message. For instance,
when inet_dgram() can't resolve the parameter host, which errno code
should it use? What if it can't resolve parameter localaddr?
Clue: many backends already report errors in their open methods.
Let's revert the flawed commit along with its dependencies, and fix up
the silent error paths instead.
This reverts commit 6e1db57b2a.
Conflicts:
console.c
hw/baum.c
qemu-char.c
This reverts commit aad04cd024.
The parts of commit db418a0a "Add stdio char device on windows" that
depend on the reverted change fixed up.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Define a state callback and make that generate chardev open/close events when
called by the spice-server.
Notes:
1) For all but the newest spice-server versions (which have a fix for this)
the code ignores these events for a spicevmc with a subtype of vdagent, this
subtype specific knowledge is undesirable, but unavoidable for now, see:
http://lists.freedesktop.org/archives/spice-devel/2011-July/004837.html
2) This code deliberately sends the events immediately rather then from a
bh. This is done this way because:
a) There is no need to do it from a bh; and
b) Doing it from a bh actually causes issues because the spice-server may send
data immediately after the open and when the open runs from a bh, then
qemu_chr_be_can_write will return 0 for the first write which the spice-server
does not expect, when this happens the spice-server will never retry the write
causing communication to stall.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Use the correct printf format string character (%z) for ssize_t.
This fixes a compile failure on 32 bit Linux with spice enabled.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
The only way for chardev drivers to communicate an error was to return a NULL
pointer, which resulted in an error message that said _that_ something went
wrong, but not _why_.
This patch changes the interface to return 0/-errno and updates
qemu_chr_open_opts to use strerror to display a more helpful error message.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
In the old spice-vmc device we used to have:
last_out = virtio_serial_write(&svc->port, p, MIN(len, VMC_MAX_HOST_WRITE));
if (last_out > 0)
...
Now in the chardev backend we have:
last_out = MIN(len, VMC_MAX_HOST_WRITE);
qemu_chr_read(scd->chr, p, last_out);
if (last_out > 0) {
...
Which causes us to no longer detect if the virtio port is not ready
to receive data from us. chardev actually has a mechanism to detect this,
but it requires a separate call to qemu_chr_can_read, before calling
qemu_chr_read (which return void).
This patch uses qemu_chr_can_read to fix the flow control from client to
guest.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Note the vmc_register_interface() in spice_chr_write is left in place
in case someone uses spice-chardev with a frontend which does not have
guest open / close notification.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Alon Levy <alevy@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Adding a chardev backend for spice, where spice determines what
to do with it based on the name attribute given during chardev creation.
For usage by spice vdagent in conjunction with a properly named
virtio-serial device, and future smartcard channel usage.
Example usage:
qemu -device virtio-serial -chardev spicevmc,name=vdagent,id=vdagent \
-device virtserialport,chardev=vdagent,name=com.redhat.spice.0
v4->v5:
* add tracing events
* fix missing comma
* fix help string to show debug is optional
v3->v4:
* updated commit message
v1->v3 changes: (v2 had a wrong commit message)
* removed spice-qemu-char.h, folded into ui/qemu-spice.h
* removed dead IOCTL code
* removed comment
* removed ifdef CONFIG_SPICE from qemu-config.c and qemu-options.hx help.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
