hw/usb/bus.c: Handle "no speed matched" case in usb_mask_to_str()

In usb_mask_to_str() we convert a mask of USB speeds into
a human-readable string (like "full+high") for use in
tracing and error me

hw/usb/bus.c: Handle "no speed matched" case in usb_mask_to_str()

In usb_mask_to_str() we convert a mask of USB speeds into
a human-readable string (like "full+high") for use in
tracing and error messages. However the conversion code
doesn't do anything to the string buffer if the passed in
speedmask doesn't match any of the recognized speeds,
which means that the tracing and error messages will
end up with random garbage in them. This can happen if
we're doing USB device passthrough.

Handle the "unrecognized speed" case by using the
string "unknown".

Fixes: https://bugs.launchpad.net/qemu/+bug/1603785
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20190328133503.6490-1-peter.maydell@linaro.org
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

show more ...

usb: drop unnecessary usb_device_post_load checks

In usb_device_post_load, certain values of dev->setup_len or
dev->setup_index can cause -EINVAL to be returned. One example is when
setup_len exceed

usb: drop unnecessary usb_device_post_load checks

In usb_device_post_load, certain values of dev->setup_len or
dev->setup_index can cause -EINVAL to be returned. One example is when
setup_len exceeds 4096, the hard-coded value of sizeof(dev->data_buf).
This can happen through legitimate guest activity and will cause all
subsequent attempts to migrate the guest to fail in vmstate_load_state.

The values of these variables can be set by USB packets originating in
the guest. There are two ways in which they can be set: in
do_token_setup and in do_parameter in hw/usb/core.c.

It is easy to craft a USB packet in a guest that causes do_token_setup
to set setup_len to a value larger than 4096. When this has been done
once, all subsequent attempts to migrate the VM will fail in
usb_device_post_load until the VM is next power-cycled or a
smaller-sized USB packet is sent to the device.

Sample code for achieving this in a VM started with "-device usb-tablet"
running Linux with CONFIG_HIDRAW=y and HID_MAX_BUFFER_SIZE > 4096:

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

int main() {
char buf[4097];
int fd = open("/dev/hidraw0", O_RDWR|O_NONBLOCK);

buf[0] = 0x1;
write(fd, buf, 4097);

return 0;
}

When this code is run in the VM, qemu will output:

usb_generic_handle_packet: ctrl buffer too small (4097 > 4096)

A subsequent attempt to migrate the VM will fail and output the
following on the destination host:

qemu-kvm: error while loading state for instance 0x0 of device '0000:00:06.7/1/usb-ptr'
qemu-kvm: load of migration failed: Invalid argument

The idea behind checking the values of setup_len and setup_index before
they are used is correct, but doing it in usb_device_post_load feels
arbitrary, and will cause unnecessary migration failures. Indeed, none
of the commit messages for c60174e8, 9f8e9895 and 719ffe1f justify why
post_load is the right place to do these checks. They correctly point
out that the important thing to protect is the usb_packet_copy.

Instead, the right place to do the checks is in do_token_setup and
do_parameter. Indeed, there are already some checks here. We can examine
each of the disjuncts currently tested in usb_device_post_load to see
whether any need adding to do_token_setup or do_parameter to improve
safety there:

* dev->setup_index < 0
- This test is not needed because setup_index is explicitly set to
0 in do_token_setup and do_parameter.

* dev->setup_len < 0
- In both do_token_setup and do_parameter, the value of setup_len
is computed by (s->setup_buf[7] << 8) | s->setup_buf[6]. Since
s->setup_buf is a byte array and setup_len is an int32_t, it's
impossible for this arithmetic to set setup_len's top bit, so it can
never be negative.

* dev->setup_index > dev->setup_len
- Since setup_index is 0, this is equivalent to the previous test,
so is redundant.

* dev->setup_len > sizeof(dev->data_buf)
- This condition is already explicitly checked in both
do_token_setup and do_parameter.

Hence there is no need to bolster the existing checks in do_token_setup
or do_parameter, and we can safely remove these checks from
usb_device_post_load without reducing safety but allowing migrations to
proceed regardless of what USB packets have been generated by the guest.

Signed-off-by: Jonathan Davies <jonathan.davies@nutanix.com>
Message-Id: <20190107175117.23769-1-jonathan.davies@nutanix.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

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error: Fix use of error_prepend() with &error_fatal, &error_abort

From include/qapi/error.h:

* Pass an existing error to the caller with the message modified:
* error_propagate(errp, err);

error: Fix use of error_prepend() with &error_fatal, &error_abort

From include/qapi/error.h:

* Pass an existing error to the caller with the message modified:
* error_propagate(errp, err);
* error_prepend(errp, "Could not frobnicate '%s': ", name);

Fei Li pointed out that doing error_propagate() first doesn't work
well when @errp is &error_fatal or &error_abort: the error_prepend()
is never reached.

Since I doubt fixing the documentation will stop people from getting
it wrong, introduce error_propagate_prepend(), in the hope that it
lures people away from using its constituents in the wrong order.
Update the instructions in error.h accordingly.

Convert existing error_prepend() next to error_propagate to
error_propagate_prepend(). If any of these get reached with
&error_fatal or &error_abort, the error messages improve. I didn't
check whether that's the case anywhere.

Cc: Fei Li <fli@suse.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20181017082702.5581-2-armbru@redhat.com>

show more ...

hmp-commands: Remove the deprecated usb_add and usb_del

It's easy to use device_add and device_del as replacement instead.
The usb_add and usb_del commands are deprecated since QEMU 2.10,
and nobody

hmp-commands: Remove the deprecated usb_add and usb_del

It's easy to use device_add and device_del as replacement instead.
The usb_add and usb_del commands are deprecated since QEMU 2.10,
and nobody complained that they are still needed, so let's get rid
of them now to make the HMP interface a little bit less overloaded.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <1512073140-17672-1-git-send-email-thuth@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

show more ...

hw/usb/bus: Remove bad object_unparent() from usb_try_create_simple()

Valgrind detects an invalid read operation when hot-plugging of an
USB device fails:

$ valgrind x86_64-softmmu/qemu-system-x86_

hw/usb/bus: Remove bad object_unparent() from usb_try_create_simple()

Valgrind detects an invalid read operation when hot-plugging of an
USB device fails:

$ valgrind x86_64-softmmu/qemu-system-x86_64 -device usb-ehci -nographic -S
==30598== Memcheck, a memory error detector
==30598== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==30598== Using Valgrind-3.12.0 and LibVEX; rerun with -h for copyright info
==30598== Command: x86_64-softmmu/qemu-system-x86_64 -device usb-ehci -nographic -S
==30598==
QEMU 2.10.50 monitor - type 'help' for more information
(qemu) device_add usb-tablet
(qemu) device_add usb-tablet
(qemu) device_add usb-tablet
(qemu) device_add usb-tablet
(qemu) device_add usb-tablet
(qemu) device_add usb-tablet
==30598== Invalid read of size 8
==30598== at 0x60EF50: object_unparent (object.c:445)
==30598== by 0x580F0D: usb_try_create_simple (bus.c:346)
==30598== by 0x581BEB: usb_claim_port (bus.c:451)
==30598== by 0x582310: usb_qdev_realize (bus.c:257)
==30598== by 0x4CB399: device_set_realized (qdev.c:914)
==30598== by 0x60E26D: property_set_bool (object.c:1886)
==30598== by 0x61235E: object_property_set_qobject (qom-qobject.c:27)
==30598== by 0x61000F: object_property_set_bool (object.c:1162)
==30598== by 0x4567C3: qdev_device_add (qdev-monitor.c:630)
==30598== by 0x456D52: qmp_device_add (qdev-monitor.c:807)
==30598== by 0x470A99: hmp_device_add (hmp.c:1933)
==30598== by 0x3679C3: handle_hmp_command (monitor.c:3123)

The object_unparent() here is not necessary anymore since commit
69382d8b3e8600b3 ("qdev: Fix object reference leak in case device.realize()
fails"), so let's remove it now.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-id: 1506526106-30971-1-git-send-email-thuth@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

show more ...

usb: Fix build with newer gcc

gcc 7 is pickier about our sources:

hw/usb/bus.c: In function ‘usb_port_location’:
hw/usb/bus.c:410:66: error: ‘%d’ directive output may be truncated writing between 1

usb: Fix build with newer gcc

gcc 7 is pickier about our sources:

hw/usb/bus.c: In function ‘usb_port_location’:
hw/usb/bus.c:410:66: error: ‘%d’ directive output may be truncated writing between 1 and 11 bytes into a region of size between 0 and 15 [-Werror=format-truncation=]
snprintf(downstream->path, sizeof(downstream->path), "%s.%d",
^~
hw/usb/bus.c:410:9: note: ‘snprintf’ output between 3 and 28 bytes into a destination of size 16
snprintf(downstream->path, sizeof(downstream->path), "%s.%d",
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
upstream->path, portnr);
~~~~~~~~~~~~~~~~~~~~~~~

But we know that there are at most 5 levels of USB hubs, with at
most two digits per level; that plus the separating dots means we
use at most 15 bytes (including trailing NUL) of our 16-byte field.
Adding an assertion to show gcc that we checked for truncation is
enough to shut up the false-positive warning.

Inspired by an idea by Dr. David Alan Gilbert <dgilbert@redhat.com>.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20170717151334.17954-1-eblake@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

show more ...

error: Apply error_propagate_null.cocci again

Signed-off-by: Fam Zheng <famz@redhat.com>
Message-Id: <20170421122710.15373-15-famz@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Revi

error: Apply error_propagate_null.cocci again

Signed-off-by: Fam Zheng <famz@redhat.com>
Message-Id: <20170421122710.15373-15-famz@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

show more ...

migrate: Introduce a 'dc->vmsd' check to avoid segfault for --only-migratable

Commit a3a3d8c7 introduced a segfault bug while checking for
'dc->vmsd->unmigratable' which caused QEMU to crash when tr

migrate: Introduce a 'dc->vmsd' check to avoid segfault for --only-migratable

Commit a3a3d8c7 introduced a segfault bug while checking for
'dc->vmsd->unmigratable' which caused QEMU to crash when trying to add
devices which do no set their 'dc->vmsd' yet while initialization.
Place a 'dc->vmsd' check prior to it so that we do not segfault for
such devices.

NOTE: This doesn't compromise the functioning of --only-migratable
option as all the unmigratable devices do set their 'dc->vmsd'.

Introduce a new function check_migratable() and move the
only_migratable check inside it, also use stubs to avoid user-mode qemu
build failures.

Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com>
Message-Id: <1487009088-23891-1-git-send-email-ashijeetacharya@gmail.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

show more ...

usb: replace handle_destroy with unrealize

Curiously, unrealize() is not being used, but it seems more
appropriate than handle_destroy() together with realize(). It is more
ubiquitous destroy name i

usb: replace handle_destroy with unrealize

Curiously, unrealize() is not being used, but it seems more
appropriate than handle_destroy() together with realize(). It is more
ubiquitous destroy name in qemu code base and may throw errors.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 20170221141451.28305-25-marcandre.lureau@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

show more ...

migration: Allow "device add" options to only add migratable devices

Introduce checks for the unmigratable flag in the VMStateDescription
structs of respective devices when user attempts to add them

migration: Allow "device add" options to only add migratable devices

Introduce checks for the unmigratable flag in the VMStateDescription
structs of respective devices when user attempts to add them. If the
"--only-migratable" was specified, all unmigratable devices will
rightly fail to add. This feature is made compatible for both "-device"
and "-usbdevice" command line options and covers their hmp and qmp
counterparts as well.

Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com>
Message-Id: <1484566314-3987-4-git-send-email-ashijeetacharya@gmail.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

show more ...

usb: free USBDevice.strings

The list is created during instance init and further populated with
usb_desc_set_string(). Clear it when unrealizing the device.

Signed-off-by: Marc-André Lureau <marcan

usb: free USBDevice.strings

The list is created during instance init and further populated with
usb_desc_set_string(). Clear it when unrealizing the device.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>

show more ...

usb: Add QOM property "attached".

USB devices in attached state are visible to the guest. This patch adds
a QOM property for this. Write access is opt-in per device. Some
devices manage attached

usb: Add QOM property "attached".

USB devices in attached state are visible to the guest. This patch adds
a QOM property for this. Write access is opt-in per device. Some
devices manage attached state automatically (usb-host, usb-serial,
usb-redir), so we can't enable write access universally but have to do
it on a case by case base. So far, no device opts in.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-id: 1465984019-28963-4-git-send-email-kraxel@redhat.com

[ minor codestyle fix ]

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

show more ...

usb: make USBDevice->attached bool

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-id: 1465984019-28963-3-git-send-email-kraxel@redhat.com

util: move declarations out of qemu-common.h

Move declarations out of qemu-common.h for functions declared in
utils/ files: e.g. include/qemu/path.h for utils/path.c.
Move inline functions out of qe

util: move declarations out of qemu-common.h

Move declarations out of qemu-common.h for functions declared in
utils/ files: e.g. include/qemu/path.h for utils/path.c.
Move inline functions out of qemu-common.h and into new files (e.g.
include/qemu/bcd.h)

Signed-off-by: Veronia Bahaa <veroniabahaa@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

show more ...

include/qemu/osdep.h: Don't include qapi/error.h

Commit 57cb38b included qapi/error.h into qemu/osdep.h to get the
Error typedef. Since then, we've moved to include qemu/osdep.h
everywhere. Its fi

include/qemu/osdep.h: Don't include qapi/error.h

Commit 57cb38b included qapi/error.h into qemu/osdep.h to get the
Error typedef. Since then, we've moved to include qemu/osdep.h
everywhere. Its file comment explains: "To avoid getting into
possible circular include dependencies, this file should not include
any other QEMU headers, with the exceptions of config-host.h,
compiler.h, os-posix.h and os-win32.h, all of which are doing a
similar job to this file and are under similar constraints."
qapi/error.h doesn't do a similar job, and it doesn't adhere to
similar constraints: it includes qapi-types.h. That's in excess of
100KiB of crap most .c files don't actually need.

Add the typedef to qemu/typedefs.h, and include that instead of
qapi/error.h. Include qapi/error.h in .c files that need it and don't
get it now. Include qapi-types.h in qom/object.h for uint16List.

Update scripts/clean-includes accordingly. Update it further to match
reality: replace config.h by config-target.h, add sysemu/os-posix.h,
sysemu/os-win32.h. Update the list of includes in the qemu/osdep.h
comment quoted above similarly.

This reduces the number of objects depending on qapi/error.h from "all
of them" to less than a third. Unfortunately, the number depending on
qapi-types.h shrinks only a little. More work is needed for that one.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
[Fix compilation without the spice devel packages. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

show more ...

usb: Clean up includes

Clean up includes so that osdep.h is included first and headers
which it implies are not included manually.

This commit was created with scripts/clean-includes.

Signed-off-b

usb: Clean up includes

Clean up includes so that osdep.h is included first and headers
which it implies are not included manually.

This commit was created with scripts/clean-includes.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1453832250-766-20-git-send-email-peter.maydell@linaro.org

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error: Use error_prepend() where it makes obvious sense

Done with this Coccinelle semantic patch

@@
expression FMT, E1, E2;
expression list ARGS;
@@
- error_setg(E1, FMT, ARG

error: Use error_prepend() where it makes obvious sense

Done with this Coccinelle semantic patch

@@
expression FMT, E1, E2;
expression list ARGS;
@@
- error_setg(E1, FMT, ARGS, error_get_pretty(E2));
+ error_propagate(E1, E2);/*###*/
+ error_prepend(E1, FMT/*@@@*/, ARGS);

followed by manual cleanup, first because I can't figure out how to
make Coccinelle transform strings, and second to get rid of now
superfluous error_propagate().

We now use or propagate the original error whole instead of just its
message obtained with error_get_pretty(). This avoids suppressing its
hint (see commit 50b7b00), but I can't see how the errors touched in
this commit could come with hints. It also improves the message
printed with &error_abort when we screw up (see commit 1e9b65b).

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

show more ...

error: Use error_reportf_err() where it makes obvious sense

Done with this Coccinelle semantic patch

@@
expression FMT, E, S;
expression list ARGS;
@@
- error_report(FMT, ARG

error: Use error_reportf_err() where it makes obvious sense

Done with this Coccinelle semantic patch

@@
expression FMT, E, S;
expression list ARGS;
@@
- error_report(FMT, ARGS, error_get_pretty(E));
+ error_reportf_err(E, FMT/*@@@*/, ARGS);
(
- error_free(E);
|
exit(S);
|
abort();
)

followed by a replace of '%s"/*@@@*/' by '"' and some line rewrapping,
because I can't figure out how to make Coccinelle transform strings.

We now use the error whole instead of just its message obtained with
error_get_pretty(). This avoids suppressing its hint (see commit
50b7b00), but I can't see how the errors touched in this commit could
come with hints.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1450452927-8346-12-git-send-email-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

show more ...

usb: print device id in "info usb" monitor command

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

qerror: Move #include out of qerror.h

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by:

qerror: Move #include out of qerror.h

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>

show more ...

usb: Improve companion configuration error messages

The previous commit broke the additional messages explaining the error
messages. Improve the error messages, so they don't need explaining
so muc

usb: Improve companion configuration error messages

The previous commit broke the additional messages explaining the error
messages. Improve the error messages, so they don't need explaining
so much. Helps QMP users as well, unlike additional explanations.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

show more ...

usb: Propagate errors through usb_register_companion()

This loses the messages explaining the error printed with
error_printf_unless_qmp(). The next commit will make up for the loss.

Signed-off-by

usb: Propagate errors through usb_register_companion()

This loses the messages explaining the error printed with
error_printf_unless_qmp(). The next commit will make up for the loss.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

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hmp: Name HMP info handler functions hmp_info_SUBCOMMAND()

Some are called do_info_SUBCOMMAND() (old ones, usually), some
hmp_info_SUBCOMMAND(), some SUBCOMMAND_info(), sometimes SUBCOMMAND
pointles

hmp: Name HMP info handler functions hmp_info_SUBCOMMAND()

Some are called do_info_SUBCOMMAND() (old ones, usually), some
hmp_info_SUBCOMMAND(), some SUBCOMMAND_info(), sometimes SUBCOMMAND
pointlessly differs in spelling.

Normalize to hmp_info_SUBCOMMAND(), where SUBCOMMAND is exactly the
subcommand name with '-' replaced by '_'.

Exceptions:

* sun4m_irq_info(), sun4m_pic_info() renamed to sun4m_hmp_info_irq(),
sun4m_hmp_info_pic().

* lm32_irq_info(), lm32_pic_info() renamed to lm32_hmp_info_irq(),
lm32_hmp_info_pic().

Signed-off-by: Markus Armbruster <armbru@redhat.com>

show more ...

usb: Change usb_create_simple() to abort on failure

Instead of returning null pointer. Matches pci_create_simple(),
isa_create_simple(), sysbus_create_simple(). It's unused since the
previous comm

usb: Change usb_create_simple() to abort on failure

Instead of returning null pointer. Matches pci_create_simple(),
isa_create_simple(), sysbus_create_simple(). It's unused since the
previous commit, but I'll put it to use again shortly.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

show more ...

usb: Suppress bogus error when automatic usb-hub creation fails

USBDevice's realize method usb_qdev_realize() automatically creates a
usb-hub when only one port is left. Creating devices in realize

usb: Suppress bogus error when automatic usb-hub creation fails

USBDevice's realize method usb_qdev_realize() automatically creates a
usb-hub when only one port is left. Creating devices in realize
methods is questionable, but works.

If usb-hub creation fails, an error is reported to stderr, but the
failure is otherwise ignored. We then create the actual device using
the last port, which may well succeed.

Example:

$ qemu -nodefaults -S -display none -machine usb=on -monitor stdio
QEMU 2.2.50 monitor - type 'help' for more information
(qemu) device_add usb-mouse
[Repeat 36 times]
(qemu) info usb
Device 0.0, Port 1, Speed 12 Mb/s, Product QEMU USB Mouse
Device 0.0, Port 2, Speed 12 Mb/s, Product QEMU USB Hub
Device 0.0, Port 2.1, Speed 12 Mb/s, Product QEMU USB Mouse
[More mice and hubs omitted...]
Device 0.0, Port 2.8.8.8.8.7, Speed 12 Mb/s, Product QEMU USB Mouse
(qemu) device_add usb-mouse
usb hub chain too deep
Failed to initialize USB device 'usb-hub'
(qemu) info usb
[...]
Device 0.0, Port 2.8.8.8.8.7, Speed 12 Mb/s, Product QEMU USB Mouse
Device 0.0, Port 2.8.8.8.8.8, Speed 12 Mb/s, Product QEMU USB Mouse

Despite the "Failed" message, the command actually succeeded.

In QMP, it's worse. When adding the 37th mouse via QMP, the command
fails with

{"error": {"class": "GenericError", "desc": "usb hub chain too deep"}}

Additionally, "Failed to initialize USB device 'usb-hub'" is reported
on stderr. Despite the command failure, the device was created. This
is wrong.

Fix by avoiding qdev_init() for usb-hub creation, so we can ignore
errors cleanly.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

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