QOM infrastructure fixes and device conversions

* Conversion of cadence_uart to QOM realize
* qom-tree QMP script
* qom-list and qom-set HMP commands to match their QMP counterparts
* Basic qom-tree HMP command
* Cleanups for /machine QOM composition tree

# gpg: Signature made Tue Mar 17 15:02:57 2015 GMT using RSA key ID 3E7E013F
# gpg: Good signature from "Andreas Färber <afaerber@suse.de>"
# gpg:                 aka "Andreas Färber <afaerber@suse.com>"

* remotes/afaerber/tags/qom-devices-for-peter:
  qdev: Move owner-less IRQs to /machine/unattached
  memory: Move owner-less MemoryRegions to /machine/unattached
  qom: Implement info qom-tree HMP command
  qom: Implement qom-set HMP command
  qom: Implement qom-list HMP command
  scripts: Add qom-tree script
  cadence_uart: Convert to QOM realize()
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

Move non-qdev-gpio[*] from /machine into /machine/unattached.
For the PC this moves 25 nodes from the stable namespace into the unstable.

Cc: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Tested-by: NAlistair Francis <alistair.francis@xilinx.com>
Signed-off-by: NAndreas Färber <afaerber@suse.de>

This cleans up the official /machine namespace. In particular
/machine/system[0] and /machine/io[0], as well as entries with
non-sanitized node names such as "/machine/qemu extended regs[0]".

The actual MemoryRegion names remain unchanged.
Acked-by: NPaolo Bonzini <pbonzini@redhat.com>
Tested-by: NAlistair Francis <alistair.francis@xilinx.com>
Signed-off-by: NAndreas Färber <afaerber@suse.de>

To complement qdev's bus-oriented info qtree, info qom-tree
prints a hierarchical view of the QOM composition tree.

By default, the machine composition tree is shown. This can be overriden
by supplying a path argument, such as "info qom-tree /".
Tested-by: NAlistair Francis <alistair.francis@xilinx.com>
Signed-off-by: NAndreas Färber <afaerber@suse.de>

Re-implemented based on qmp_qom_set() to facilitate argument parsing.

Warn about ambiguous path arguments.
Reviewed-by: NGonglei <arei.gonglei@huawei.com>
Tested-by: NAlistair Francis <alistair.francis@xilinx.com>
Signed-off-by: NAndreas Färber <afaerber@suse.de>

Implement it as a wrapper for QMP qom-list, but mimic the behavior of
scripts/qmp/qom-list in making the path argument optional and listing
the root if absent, to hint users what kind of path to pass.
Reviewed-by: NGonglei <arei.gonglei@huawei.com>
Tested-by: NAlistair Francis <alistair.francis@xilinx.com>
Signed-off-by: NAndreas Färber <afaerber@suse.de>

Functionally it is a recursive qom-list with qom-get per non-child<>
property. Some failures needed to be handled, such as trying to read a
pointer property, which is not representable in QMP. Those print a
literal "<EXCEPTION>".
Tested-by: NAlistair Francis <alistair.francis@xilinx.com>
Signed-off-by: NAndreas Färber <afaerber@suse.de>

Use DeviceClass::realize() and TypeInfo::instance_init() instead of
the deprecated SysBusDevice::init().
Signed-off-by: NAlistair Francis <alistair.francis@xilinx.com>
Reviewed-by: NPeter Crosthwaite <peter.crosthwaite@xilinx.com>
Signed-off-by: NAndreas Färber <afaerber@suse.de>

coverity: Fix g_malloc_n-like models

# gpg: Signature made Tue Mar 17 10:17:56 2015 GMT using RSA key ID EB918653
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>"
# gpg:                 aka "Markus Armbruster <armbru@pond.sub.org>"

* remotes/armbru/tags/pull-cov-model-2015-03-17:
  coverity: Fix g_malloc_n-like models
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

opengl: fix configure test

# gpg: Signature made Tue Mar 17 10:11:24 2015 GMT using RSA key ID D3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>"
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>"
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>"

* remotes/kraxel/tags/pull-gl-20150317-1:
  opengl: fix configure test
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

Re-add the glx compile test to configure.  We can't use pkg-config to
probe for glx, and as long as milkymist-tmu2 privately uses glx (due to
opengl infrastructure in qemu not being ready yet) we must continue to
test for glx to avoid build failures.
Reported-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>

Allocate the calculated overall size, not only the size of a single
element.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>

Block patches for 2.3-rc0

# gpg: Signature made Mon Mar 16 16:11:55 2015 GMT using RSA key ID C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>"

* remotes/kevin/tags/for-upstream:
  block/vpc: remove disabled code from get_sector_offset
  block/vpc: rename footer->size -> footer->current_size
  block/vpc: make calculate_geometry spec conform
  vpc: Ignore geometry for large images
  block/vpc: optimize vpc_co_get_block_status
  block: Drop bdrv_find
  blockdev: Convert bdrv_find to blk_by_name
  migration: Convert bdrv_find to blk_by_name
  monitor: Convert bdrv_find to blk_by_name
  iotests: Test non-self-referential qcow2 refblocks
  iotests: Add tests for refcount table growth
  qcow2: Respect new_block in alloc_refcount_block()
  qemu-img: Avoid qerror_report_err() outside QMP handlers, again
  block: Fix block-set-write-threshold not to use funky error class
  block: Deprecate QCOW/QCOW2 encryption
  qemu-img: Fix convert, amend error messages for unknown options
  iotests: Update 051's reference output
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

TriCore RRR1, RRRR, RRRW, and SYS instructions

# gpg: Signature made Mon Mar 16 15:55:24 2015 GMT using RSA key ID 6B69CA14
# gpg: Good signature from "Bastian Koppelmann <kbastian@mail.uni-paderborn.de>"

* remotes/bkoppelmann/tags/pull-tricore-20150316:
  target-tricore: Add instructions of SYS opcode format
  target-tricore: Add instructions of RRRW opcode format
  target-tricore: Add instructions of RRRR opcode format
  target-tricore: Add instructions of RRR1 opcode format, which have 0xe3 as first opcode
  target-tricore: Add instructions of RRR1 opcode format, which have 0x63 as first opcode
  target-tricore: Add instructions of RRR1 opcode format, which have 0xa3 as first opcode
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

tcg opt fix for or x,a,a

# gpg: Signature made Mon Mar 16 15:47:19 2015 GMT using RSA key ID 4DD0279B
# gpg: Good signature from "Richard Henderson <rth7680@gmail.com>"
# gpg:                 aka "Richard Henderson <rth@redhat.com>"
# gpg:                 aka "Richard Henderson <rth@twiddle.net>"

* remotes/rth/tags/tcg-pull-20150316:
  tcg/optimize: Handle or r,a,a with constant a
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

* mreitz/block:
  block/vpc: remove disabled code from get_sector_offset
  block/vpc: rename footer->size -> footer->current_size
  block/vpc: make calculate_geometry spec conform
  vpc: Ignore geometry for large images
  block/vpc: optimize vpc_co_get_block_status
  block: Drop bdrv_find
  blockdev: Convert bdrv_find to blk_by_name
  migration: Convert bdrv_find to blk_by_name
  monitor: Convert bdrv_find to blk_by_name
  iotests: Test non-self-referential qcow2 refblocks
  iotests: Add tests for refcount table growth
  qcow2: Respect new_block in alloc_refcount_block()

The code to check the bitmap for the allocation status of each sector
has been "disabled by reason" ever since the vpc driver existed.

The reason might be that we might end up reading sector by sector
in vpc_read if we really used it. This would be a performance desaster.

The current code would furthermore not work if the disabled parts get
reactivated since vpc_read and vpc_write only use get_sector_offset to
check the allocation status of the first sector of a read/write operation.
This might lead to sectors incorrectly treated as zero in vpc_read and
to sectors getting allocated twice in vpc_write.
Signed-off-by: NPeter Lieven <pl@kamp.de>
Message-id: 1425379316-19639-6-git-send-email-pl@kamp.de
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NMax Reitz <mreitz@redhat.com>

the field is named current size in the spec. Name it accordingly.
Signed-off-by: NPeter Lieven <pl@kamp.de>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Message-id: 1425379316-19639-5-git-send-email-pl@kamp.de
Signed-off-by: NMax Reitz <mreitz@redhat.com>

The VHD spec [1] allows for total_sectors of 65535 x 16 x 255 (~127GB)
represented by a CHS geometry. If total_sectors is greater
than 65535 x 16 x 255 this geometry is set as a maximum.

Qemu, Hyper-V and disk2vhd use this special geometry as an indicator
to use the image current size from the footer as disk size.

This patch changes vpc_create to effectively calculate a CxHxS geometry
for the given image size if possible while rounding up if necessary.
If the image size is too big to be represented in CHS we set the maximum
and write the exact requested image size into the footer.

This partly reverts commit 258d2edb, but leaves support for >127G disks
intact.

[1] http://download.microsoft.com/download/f/f/e/ffef50a5-07dd-4cf8-aaa3-442c0673a029/Virtual%20Hard%20Disk%20Format%20Spec_10_18_06.docSigned-off-by: NPeter Lieven <pl@kamp.de>
Message-id: 1425379316-19639-4-git-send-email-pl@kamp.de
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NMax Reitz <mreitz@redhat.com>

The CHS calculation as done per the VHD spec imposes a maximum image
size of ~127 GB. Real VHD images exist that are larger than that.

Apparently there are two separate non-standard ways to achieve this:
You could use more heads than the spec does - this is the option that
qemu-img create chooses.

However, other images exist where the geometry is set to the maximum
(65535/16/255), but the actual image size is larger. Until now, such
images are truncated at 127 GB when opening them with qemu.

This patch changes the vpc driver to ignore geometry in this case and
only trust the size field in the header.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
[PL: Fixed maximum geometry in the commit msg]
Signed-off-by: NPeter Lieven <pl@kamp.de>
Message-id: 1425379316-19639-3-git-send-email-pl@kamp.de
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NMax Reitz <mreitz@redhat.com>

*pnum can't be greater than s->block_size / BDRV_SECTOR_SIZE for allocated
sectors since there is always a bitmap in between.
Signed-off-by: NPeter Lieven <pl@kamp.de>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Message-id: 1425379316-19639-2-git-send-email-pl@kamp.de
Signed-off-by: NMax Reitz <mreitz@redhat.com>

All callers are converted, so drop it.
Signed-off-by: NFam Zheng <famz@redhat.com>
Message-id: 1425296209-1476-5-git-send-email-famz@redhat.com
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NMax Reitz <mreitz@redhat.com>

Signed-off-by: NFam Zheng <famz@redhat.com>
Message-id: 1425296209-1476-4-git-send-email-famz@redhat.com
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NMax Reitz <mreitz@redhat.com>

Signed-off-by: NFam Zheng <famz@redhat.com>
Message-id: 1425296209-1476-3-git-send-email-famz@redhat.com
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NMax Reitz <mreitz@redhat.com>

Signed-off-by: NFam Zheng <famz@redhat.com>
Message-id: 1425296209-1476-2-git-send-email-famz@redhat.com
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NMax Reitz <mreitz@redhat.com>

It is easy to create only self-referential refblocks, but there are
cases where that is impossible. This adds a test for two of those cases
(combined in a single test case).
Suggested-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Message-id: 1417798412-15330-1-git-send-email-mreitz@redhat.com
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NMax Reitz <mreitz@redhat.com>

Signed-off-by: NMax Reitz <mreitz@redhat.com>
Message-id: 1423598552-24301-3-git-send-email-mreitz@redhat.com
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Signed-off-by: NMax Reitz <mreitz@redhat.com>

When choosing a new place for the refcount table, alloc_refcount_block()
tries to infer the number of clusters used so far from its argument
cluster_index (which comes from the idea that if any cluster with an
index greater than cluster_index was in use, the refcount table would
have to be big enough already to describe cluster_index).

However, there is a cluster that may be at or after cluster_index, and
which is not covered by the refcount structures, and that is the new
refcount block new_block. Therefore, it should be taken into account for
the blocks_used calculation.

Also, because new_block already describes (or is intended to describe)
cluster_index, we may not put the new refcount structures there.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Message-id: 1423598552-24301-2-git-send-email-mreitz@redhat.com
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Signed-off-by: NMax Reitz <mreitz@redhat.com>

qerror_report_err() is a transitional interface to help with
converting existing monitor commands to QMP.  It should not be used
elsewhere.  Replace by error_report_err().

Commit 6936f299 cleaned that up in qemu-img.c, but two calls have crept
in since.  Take care of them the same way.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

Error classes are a leftover from the days of "rich" error objects.
New code should always use ERROR_CLASS_GENERIC_ERROR.  Commit e2462113
added a use of ERROR_CLASS_DEVICE_NOT_FOUND.  Replace it.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

We've steered users away from QCOW/QCOW2 encryption for a while,
because it's a flawed design (commit 136cd19d Describe flaws in
qcow/qcow2 encryption in the docs).

In addition to flawed crypto, we have comically bad usability, and
plain old bugs.  Let me show you.

= Example images =

I'm going to use a raw image as backing file, and two QCOW2 images,
one encrypted, and one not:

    $ qemu-img create -f raw backing.img 4m
    Formatting 'backing.img', fmt=raw size=4194304
    $ qemu-img create -f qcow2 -o encryption,backing_file=backing.img,backing_fmt=raw geheim.qcow2 4m
    Formatting 'geheim.qcow2', fmt=qcow2 size=4194304 backing_file='backing.img' backing_fmt='raw' encryption=on cluster_size=65536 lazy_refcounts=off
    $ qemu-img create -f qcow2 -o backing_file=backing.img,backing_fmt=raw normal.qcow2 4m
    Formatting 'normal.qcow2', fmt=qcow2 size=4194304 backing_file='backing.img' backing_fmt='raw' encryption=off cluster_size=65536 lazy_refcounts=off

= Usability issues =

== Confusing startup ==

When no image is encrypted, and you don't give -S, QEMU starts the
guest immediately:

    $ qemu-system-x86_64 -nodefaults -display none -monitor stdio normal.qcow2
    QEMU 2.2.50 monitor - type 'help' for more information
    (qemu) info status
    VM status: running

But as soon as there's an encrypted image in play, the guest is *not*
started, with no notification whatsoever:

    $ qemu-system-x86_64 -nodefaults -display none -monitor stdio geheim.qcow2
    QEMU 2.2.50 monitor - type 'help' for more information
    (qemu) info status
    VM status: paused (prelaunch)

If the user figured out that he needs to type "cont" to enter his
keys, the confusion enters the next level: "cont" asks for at most
*one* key.  If more are needed, it then silently does nothing.  The
user has to type "cont" once per encrypted image:

    $ qemu-system-x86_64 -nodefaults -display none -monitor stdio -drive if=none,file=geheim.qcow2 -drive if=none,file=geheim.qcow2
    QEMU 2.2.50 monitor - type 'help' for more information
    (qemu) info status
    VM status: paused (prelaunch)
    (qemu) c
    none0 (geheim.qcow2) is encrypted.
    Password: ******
    (qemu) info status
    VM status: paused (prelaunch)
    (qemu) c
    none1 (geheim.qcow2) is encrypted.
    Password: ******
    (qemu) info status
    VM status: running

== Incorrect passwords not caught ==

All existing encryption schemes give you the GIGO treatment: garbage
password in, garbage data out.  Guests usually refuse to mount
garbage, but other usage is prone to data loss.

== Need to stop the guest to add an encrypted image ==

    $ qemu-system-x86_64 -nodefaults -display none -monitor stdio
    QEMU 2.2.50 monitor - type 'help' for more information
    (qemu) info status
    VM status: running
    (qemu) drive_add "" if=none,file=geheim.qcow2
    Guest must be stopped for opening of encrypted image
    (qemu) stop
    (qemu) drive_add "" if=none,file=geheim.qcow2
    OK

Commit c3adb58f added this restriction.  Before, we could expose images
lacking an encryption key to guests, with potentially catastrophic
results.  See also "Use without key is not always caught".

= Bugs =

== Use without key is not always caught ==

Encrypted images can be in an intermediate state "opened, but no key".
The weird startup behavior and the need to stop the guest are there to
ensure the guest isn't exposed to that state.  But other things still
are!

* drive_backup

    $ qemu-system-x86_64 -nodefaults -display none -monitor stdio geheim.qcow2
    QEMU 2.2.50 monitor - type 'help' for more information
    (qemu) drive_backup -f ide0-hd0 out.img raw
    Formatting 'out.img', fmt=raw size=4194304

  I guess this writes encrypted data to raw image out.img.  Good luck
  with figuring out how to decrypt that again.

* commit

    $ qemu-system-x86_64 -nodefaults -display none -monitor stdio geheim.qcow2
    QEMU 2.2.50 monitor - type 'help' for more information
    (qemu) commit ide0-hd0

  I guess this writes encrypted data into the unencrypted raw backing
  image, effectively destroying it.

== QMP device_add of usb-storage fails when it shouldn't ==

When the image is encrypted, device_add creates the device, defers
actually attaching it to when the key becomes available, then fails.
This is wrong.  device_add must either create the device and succeed,
or do nothing and fail.

    $ qemu-system-x86_64 -nodefaults -display none -usb -qmp stdio -drive if=none,id=foo,file=geheim.qcow2
    {"QMP": {"version": {"qemu": {"micro": 50, "minor": 2, "major": 2}, "package": ""}, "capabilities": []}}
    { "execute": "qmp_capabilities" }
    {"return": {}}
    { "execute": "device_add", "arguments": { "driver": "usb-storage", "id": "bar", "drive": "foo" } }
    {"error": {"class": "DeviceEncrypted", "desc": "'foo' (geheim.qcow2) is encrypted"}}
    {"execute":"device_del","arguments": { "id": "bar" } }
    {"timestamp": {"seconds": 1426003440, "microseconds": 237181}, "event": "DEVICE_DELETED", "data": {"path": "/machine/peripheral/bar/bar.0/legacy[0]"}}
    {"timestamp": {"seconds": 1426003440, "microseconds": 238231}, "event": "DEVICE_DELETED", "data": {"device": "bar", "path": "/machine/peripheral/bar"}}
    {"return": {}}

This stuff is worse than useless, it's a trap for users.

If people become sufficiently interested in encrypted images to
contribute a cryptographically sane implementation for QCOW2 (or
whatever other format), then rewriting the necessary support around it
from scratch will likely be easier and yield better results than
fixing up the existing mess.

Let's deprecate the mess now, drop it after a grace period, and move
on.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

Message quality regressed in commit dc523cd3.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

Commit c4bacafb improved error reporting, but neglected to update
051.out.  Commit 2726958d tried to redress, but didn't get it quite
right (punctuation difference), and shortly after commit
ae071cc8..master improved error reporting some more, neglecting 051.out
some more.  Sorry!
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

This adds only the non trap instructions.
Signed-off-by: NBastian Koppelmann <kbastian@mail.uni-paderborn.de>

As seen with ubuntu-5.10-live-powerpc.iso.
Reported-by: NMark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Tested-by: NMark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: NBastian Koppelmann <kbastian@mail.uni-paderborn.de>
Signed-off-by: NRichard Henderson <rth@twiddle.net>

Reviewed-by: NRichard Henderson <rth@twiddle.net>
Signed-off-by: NBastian Koppelmann <kbastian@mail.uni-paderborn.de>

Reviewed-by: NRichard Henderson <rth@twiddle.net>
Signed-off-by: NBastian Koppelmann <kbastian@mail.uni-paderborn.de>

Add helpers helper_subadr_h/_ssov which subs one halfword and adds one
halfword, rounds / and saturates each half word independently.

Add microcode helper functions:
    * gen_msubad_h/ads_h: multiply two halfwords left justified and sub from the
                          first one word and add the second one word
                          / and saturate each resulting word independetly.
    * gen_msubadm_h/adms_h: multiply two halfwords in q-format left justified
                            and sub from the first one word and add to
                            the second one word / and saturate each resulting
                            word independetly.
    * gen_msubadr32_h/32s_h: multiply two halfwords in q-format left justified
                             and sub from the first one word and add to
                             the second one word, round both results / and
                             saturate each resulting word independetly.
Reviewed-by: NRichard Henderson <rth@twiddle.net>
Signed-off-by: NBastian Koppelmann <kbastian@mail.uni-paderborn.de>

Add helpers:
    * msub64_q_ssov: multiply two 32 bit q-format number, sub the result from a
                     64 bit q-format number and saturate.
    * msub32_q_sub_ssov: sub two 64 bit q-format numbers and return a 32 bit
                         result.
    * msubr_q_ssov: multiply two 32 bit q-format numbers, sub the result from a 32 bit
                    q-format number and saturate.
    * msubr_q: multiply two 32 bit q-format numbers and sub the result from a 32 bit
               q-format number.
Reviewed-by: NRichard Henderson <rth@twiddle.net>
Signed-off-by: NBastian Koppelmann <kbastian@mail.uni-paderborn.de>

Add helpers:
    * sub64_ssov: subs two 64 bit values and saturates the result.
    * subr_h/_ssov: subs two halfwords from two words in q-format with rounding
                    / and saturates each result independetly.

Add microcode generator:
    * gen_sub64_d: adds two 64 bit values.
    * gen_msub_h/s_h: multiply four halfwords, sub each result left justfied
                      from two word values / and saturate each result.
    * gen_msubm_h/s_h: multiply four halfwords, sub each result left justfied
                       from two words values in q-format / and saturate each
                       result.
    * gen_msubr32/64_h/s_h: multiply four halfwords, sub each result left
                            justfied from two halftwords/words values in q-format
                            / and saturate each result.
Reviewed-by: NRichard Henderson <rth@twiddle.net>
Signed-off-by: NBastian Koppelmann <kbastian@mail.uni-paderborn.de>