The 'Print' key is special in the AT set 1 / set 2 scancode definitions.
An unmodified 'Print' key is supposed to send
AT Set 1: e0 2a e0 37 (Down) e0 b7 e0 aa (Up)
AT Set 2: e0 12 e0 7c (Down) e0 f0 7c e0 f0 12 (Up)
which QEMU gets right. When pressed in combination with the 'Alt_L' or 'Alt_R'
keys (which signify SysRq), the scancodes are required to follow a different
scheme. With Alt_L, the expected sequences are
AT set 1: 38, 54 (Down) d4, b8 (Up)
AT set 2: 11, 84 (Down) f0 84, f0 11 (Up)
And with Alt_R
AT set 1: e0 38, 54 (Down) d4, e0 b8 (Up)
AT set 2: e0 11, 84 (Down) f0 84, f0 e0 11 (Up)
It is actually slightly more complicated than that, because (according results
of 'showkey -s', keyboards will in fact first release the currently pressed
modifier before sending the sequence above (which effectively re-presses &
then releases the modifier) and finally re-press the original modifier
afterwards. IOW, with Alt_L we need to send
AT set 1: b8, 38, 54 (Down) d4, b8, 38 (Up)
AT set 2: f0 11, 11, 84 (Down) f0 84, f0 11, 11 (Up)
And with Alt_R
AT set 1: e0 b8, e0 38, 54 (Down) d4, e0 b8, e0 38 (Up)
AT set 2: e0 f0 11, e0 11, 84 (Down) f0 84, e0 f0 11, e0 11 (Up)
The AT set 3 scancodes have no special handling for Alt-Print.
Rather than fixing the handling of the 'print' key in the ps2 driver to consider
the Alt modifiers, way back, a patch was commited that defined an extra 'sysrq'
key name:
commit f2289cb692
Author: balrog <balrog@c046a42c-6fe2-441c-8c8c-71466251a162>
Date: Wed Jun 4 10:14:16 2008 +0000
Add sysrq to key names known by "sendkey".
Adding sysrq keycode to the table enabling running sysrq debugging in
the guest via the monitor sendkey command, like:
(qemu) sendkey alt-sysrq-t
Tested on x86-64 target and Linux guest.
Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
With this patch QEMU would send
AT set 1: 38, 54 (Down) d4, b8 (Up)
AT set 2: 11, 84 (Down) f0 84, f0 11 (Up)
but this doesn't match what actual real keyboards send, as it is not releasing
the original modifier & pressing it again afterwards. In addition the original
problem remains, and a new problem was added:
- The sequence 'alt-print-t' is still broken, acting as if 'print-t' was
requested
- The sequence 'sysrq-t' is broken, injecting an undefine scancode sequence
tot he guest os (bare 0x54)
To deal with this mess we make these changes to the ps2 code, so that we track
the state of modifier keys (Alt, Shift, Ctrl - both left & right). Then we can
vary what scancodes are sent for Q_KEY_CODE_PRINT according to the Alt key
modifier state
Interestingly, it appears that of operating systems I've checked (Linux, FreeBSD
and OpenSolaris), none of them actually bother to validate the full sequences
for a unmodified 'Print' key. They all just ignore the leading "e0 2a" and
trigger based off "e0 37" alone. The latter two byte sequence is what keyboards
send with 'Print' is combined with 'Shift' or 'Ctrl' modifiers.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-id: 20171019142848.572-5-berrange@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
QEMU README
===========
QEMU is a generic and open source machine & userspace emulator and
virtualizer.
QEMU is capable of emulating a complete machine in software without any
need for hardware virtualization support. By using dynamic translation,
it achieves very good performance. QEMU can also integrate with the Xen
and KVM hypervisors to provide emulated hardware while allowing the
hypervisor to manage the CPU. With hypervisor support, QEMU can achieve
near native performance for CPUs. When QEMU emulates CPUs directly it is
capable of running operating systems made for one machine (e.g. an ARMv7
board) on a different machine (e.g. an x86_64 PC board).
QEMU is also capable of providing userspace API virtualization for Linux
and BSD kernel interfaces. This allows binaries compiled against one
architecture ABI (e.g. the Linux PPC64 ABI) to be run on a host using a
different architecture ABI (e.g. the Linux x86_64 ABI). This does not
involve any hardware emulation, simply CPU and syscall emulation.
QEMU aims to fit into a variety of use cases. It can be invoked directly
by users wishing to have full control over its behaviour and settings.
It also aims to facilitate integration into higher level management
layers, by providing a stable command line interface and monitor API.
It is commonly invoked indirectly via the libvirt library when using
open source applications such as oVirt, OpenStack and virt-manager.
QEMU as a whole is released under the GNU General Public License,
version 2. For full licensing details, consult the LICENSE file.
Building
========
QEMU is multi-platform software intended to be buildable on all modern
Linux platforms, OS-X, Win32 (via the Mingw64 toolchain) and a variety
of other UNIX targets. The simple steps to build QEMU are:
mkdir build
cd build
../configure
make
Additional information can also be found online via the QEMU website:
http://qemu-project.org/Hosts/Linux
http://qemu-project.org/Hosts/Mac
http://qemu-project.org/Hosts/W32
Submitting patches
==================
The QEMU source code is maintained under the GIT version control system.
git clone git://git.qemu-project.org/qemu.git
When submitting patches, the preferred approach is to use 'git
format-patch' and/or 'git send-email' to format & send the mail to the
qemu-devel@nongnu.org mailing list. All patches submitted must contain
a 'Signed-off-by' line from the author. Patches should follow the
guidelines set out in the HACKING and CODING_STYLE files.
Additional information on submitting patches can be found online via
the QEMU website
http://qemu-project.org/Contribute/SubmitAPatch
http://qemu-project.org/Contribute/TrivialPatches
Bug reporting
=============
The QEMU project uses Launchpad as its primary upstream bug tracker. Bugs
found when running code built from QEMU git or upstream released sources
should be reported via:
https://bugs.launchpad.net/qemu/
If using QEMU via an operating system vendor pre-built binary package, it
is preferable to report bugs to the vendor's own bug tracker first. If
the bug is also known to affect latest upstream code, it can also be
reported via launchpad.
For additional information on bug reporting consult:
http://qemu-project.org/Contribute/ReportABug
Contact
=======
The QEMU community can be contacted in a number of ways, with the two
main methods being email and IRC
- qemu-devel@nongnu.org
http://lists.nongnu.org/mailman/listinfo/qemu-devel
- #qemu on irc.oftc.net
Information on additional methods of contacting the community can be
found online via the QEMU website:
http://qemu-project.org/Contribute/StartHere
-- End