Factor out the implementation of SYS_READ via the
new function tables.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20190916141544.17540-10-peter.maydell@linaro.org

Factor out the implementation of SYS_WRITE via the
new function tables.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20190916141544.17540-9-peter.maydell@linaro.org

Currently for the semihosting calls which take a file descriptor
(SYS_CLOSE, SYS_WRITE, SYS_READ, SYS_ISTTY, SYS_SEEK, SYS_FLEN)
we have effectively two implementations, one for real host files
and one for when we indirect via the gdbstub. We want to add a
third one to deal with the magic :semihosting-features file.

Instead of having a three-way if statement in each of these
cases, factor out the implementation of the calls to separate
functions which we dispatch to via function pointers selected
via the GuestFDType for the guest fd.

In this commit, we set up the framework for the dispatch,
and convert the SYS_CLOSE call to use it.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20190916141544.17540-8-peter.maydell@linaro.org

When we are routing semihosting operations through the gdbstub, the
work of sorting out the return value and setting errno if necessary
is done by callback functions which are invoked by the gdbstub code.
Clean up some ifdeffery in those functions by having them call
set_swi_errno() to set the semihosting errno.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20190916141544.17540-7-peter.maydell@linaro.org

The semihosting code needs accuss to the linux-user only
TaskState pointer so it can set the semihosting errno per-thread
for linux-user mode. At the moment we do this by having some
ifdefs so that we define a 'ts' local in do_arm_semihosting()
which is either a real TaskState * or just a CPUARMState *,
depending on which mode we're compiling for.

This is awkward if we want to refactor do_arm_semihosting()
into other functions which might need to be passed the TaskState.
Restrict usage of the TaskState local by:
 * making set_swi_errno() always take the CPUARMState pointer
   and (for the linux-user version) get TaskState from that
 * creating a new get_swi_errno() which reads the errno
 * having the two semihosting calls which need the TaskState
   for other purposes (SYS_GET_CMDLINE and SYS_HEAPINFO)
   define a variable with scope restricted to just that code
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20190916141544.17540-6-peter.maydell@linaro.org

Currently the Arm semihosting code returns the guest file descriptors
(handles) which are simply the fd values from the host OS or the
remote gdbstub. Part of the semihosting 2.0 specification requires
that we implement special handling of opening a ":semihosting-features"
filename. Guest fds which result from opening the special file
won't correspond to host fds, so to ensure that we don't end up
with duplicate fds we need to have QEMU code control the allocation
of the fd values we give the guest.

Add in an abstraction layer which lets us allocate new guest FD
values, and translate from a guest FD value back to the host one.
This also fixes an odd hole where a semihosting guest could
use the semihosting API to read, write or close file descriptors
that it had never allocated but which were being used by QEMU itself.
(This isn't a security hole, because enabling semihosting permits
the guest to do arbitrary file access to the whole host filesystem,
and so should only be done if the guest is completely trusted.)

Currently the only kind of guest fd is one which maps to a
host fd, but in a following commit we will add one which maps
to the :semihosting-features magic data.

If the guest is migrated with an open semihosting file descriptor
then subsequent attempts to use the fd will all fail; this is
not a change from the previous situation (where the host fd
being used on the source end would not be re-opened on the
destination end).
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20190916141544.17540-5-peter.maydell@linaro.org

In arm_gdb_syscall() we have a comment suggesting a race
because the syscall completion callback might not happen
before the gdb_do_syscallv() call returns. The comment is
correct that the callback may not happen but incorrect about
the effects. Correct it and note the important caveat that
callers must never do any work of any kind after return from
arm_gdb_syscall() that depends on its return value.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20190916141544.17540-4-peter.maydell@linaro.org

If we fail a semihosting call we should always set the
semihosting errno to something; we were failing to do
this for some of the "check inputs for sanity" cases.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NAlex Bennée <alex.bennee@linaro.org>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20190916141544.17540-3-peter.maydell@linaro.org

The set_swi_errno() function is called to capture the errno
from a host system call, so that we can return -1 from the
semihosting function and later allow the guest to get a more
specific error code with the SYS_ERRNO function. It comes in
two versions, one for user-only and one for softmmu. We forgot
to capture the errno in the softmmu version; fix the error.

(Semihosting calls directed to gdb are unaffected because
they go through a different code path that captures the
error return from the gdbstub call in arm_semi_cb() or
arm_semi_flen_cb().)
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20190916141544.17540-2-peter.maydell@linaro.org

Switch the cmsdk-apb-watchdog code away from bottom-half based
ptimers to the new transaction-based ptimer API.  This just requires
adding begin/commit calls around the various places that modify the
ptimer state, and using the new ptimer_init() function to create the
timer.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-22-peter.maydell@linaro.org

Switch the cmsdk-apb-watchdog code away from bottom-half based
ptimers to the new transaction-based ptimer API.  This just requires
adding begin/commit calls around the various places that modify the
ptimer state, and using the new ptimer_init() function to create the
timer.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-21-peter.maydell@linaro.org

Switch the mss-timer code away from bottom-half based ptimers to
the new transaction-based ptimer API.  This just requires adding
begin/commit calls around the various places that modify the ptimer
state, and using the new ptimer_init() function to create the timer.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-20-peter.maydell@linaro.org

Switch the imx_epit.c code away from bottom-half based ptimers to
the new transaction-based ptimer API.  This just requires adding
begin/commit calls around the various places that modify the ptimer
state, and using the new ptimer_init() function to create the timer.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-19-peter.maydell@linaro.org

Switch the imx_epit.c code away from bottom-half based ptimers to
the new transaction-based ptimer API.  This just requires adding
begin/commit calls around the various places that modify the ptimer
state, and using the new ptimer_init() function to create the timer.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-18-peter.maydell@linaro.org

Switch the exynos41210_rtc main ptimer over to the transaction-based
API, completing the transition for this device.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-17-peter.maydell@linaro.org

Switch the exynos41210_rtc 1Hz ptimer over to the transaction-based
API. (We will switch the other ptimer used by this device in a
separate commit.)
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-16-peter.maydell@linaro.org

Switch the exynos4210_pwm code away from bottom-half based ptimers to
the new transaction-based ptimer API.  This just requires adding
begin/commit calls around the various places that modify the ptimer
state, and using the new ptimer_init() function to create the timer.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-15-peter.maydell@linaro.org

Switch the ltick ptimer over to the ptimer transaction API.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-14-peter.maydell@linaro.org

Switch the exynos MCT LFRC timers over to the ptimer transaction API.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-13-peter.maydell@linaro.org

We want to switch the exynos MCT code away from bottom-half based ptimers to
the new transaction-based ptimer API. The MCT is complicated
and uses multiple different ptimers, so it's clearer to switch
it a piece at a time. Here we change over only the GFRC.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-12-peter.maydell@linaro.org

Switch the digic-timer.c code away from bottom-half based ptimers to
the new transaction-based ptimer API.  This just requires adding
begin/commit calls around the various places that modify the ptimer
state, and using the new ptimer_init() function to create the timer.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-11-peter.maydell@linaro.org

Switch the cmsdk-apb-timer code away from bottom-half based ptimers
to the new transaction-based ptimer API.  This just requires adding
begin/commit calls around the various places that modify the ptimer
state, and using the new ptimer_init() function to create the timer.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-10-peter.maydell@linaro.org

Switch the cmsdk-apb-dualtimer code away from bottom-half based
ptimers to the new transaction-based ptimer API.  This just requires
adding begin/commit calls around the various places that modify the
ptimer state, and using the new ptimer_init() function to create the
timer.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-9-peter.maydell@linaro.org

Switch the arm_mptimer.c code away from bottom-half based ptimers to
the new transaction-based ptimer API.  This just requires adding
begin/commit calls around the various places that modify the ptimer
state, and using the new ptimer_init() function to create the timer.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-8-peter.maydell@linaro.org

Switch the allwinner-a10-pit code away from bottom-half based ptimers to
the new transaction-based ptimer API.  This just requires adding
begin/commit calls around the various places that modify the ptimer
state, and using the new ptimer_init() function to create the timer.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-7-peter.maydell@linaro.org

Switch the musicpal code away from bottom-half based ptimers to
the new transaction-based ptimer API.  This just requires adding
begin/commit calls around the various places that modify the ptimer
state, and using the new ptimer_init() function to create the timer.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-6-peter.maydell@linaro.org

Switch the arm_timer.c code away from bottom-half based ptimers
to the new transaction-based ptimer API. This just requires
adding begin/commit calls around the various arms of
arm_timer_write() that modify the ptimer state, and using the
new ptimer_init() function to create the timer.

Fixes: https://bugs.launchpad.net/qemu/+bug/1777777Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-5-peter.maydell@linaro.org

Convert the ptimer test cases to the transaction-based ptimer API,
by changing to ptimer_init(), dropping the now-unused QEMUBH
variables, and surrounding each set of changes to the ptimer
state in ptimer_transaction_begin/commit calls.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-4-peter.maydell@linaro.org

Provide the new transaction-based API. If a ptimer is created
using ptimer_init() rather than ptimer_init_with_bh(), then
instead of providing a QEMUBH, it provides a pointer to the
callback function directly, and has opted into the transaction
API. All calls to functions which modify ptimer state:
 - ptimer_set_period()
 - ptimer_set_freq()
 - ptimer_set_limit()
 - ptimer_set_count()
 - ptimer_run()
 - ptimer_stop()
must be between matched calls to ptimer_transaction_begin()
and ptimer_transaction_commit(). When ptimer_transaction_commit()
is called it will evaluate the state of the timer after all the
changes in the transaction, and call the callback if necessary.

In the old API the individual update functions generally would
call ptimer_trigger() immediately, which would schedule the QEMUBH.
In the new API the update functions will instead defer the
"set s->next_event and call ptimer_reload()" work to
ptimer_transaction_commit().

Because ptimer_trigger() can now immediately call into the
device code which may then call other ptimer functions that
update ptimer_state fields, we must be more careful in
ptimer_reload() not to cache fields from ptimer_state across
the ptimer_trigger() call. (This was harmless with the QEMUBH
mechanism as the BH would not be invoked until much later.)

We use assertions to check that:
 * the functions modifying ptimer state are not called outside
   a transaction block
 * ptimer_transaction_begin() and _commit() calls are paired
 * the transaction API is not used with a QEMUBH ptimer

There is some slight repetition of code:
 * most of the set functions have similar looking "if s->bh
   call ptimer_reload, otherwise set s->need_reload" code
 * ptimer_init() and ptimer_init_with_bh() have similar code
We deliberately don't try to avoid this repetition, because
it will all be deleted when the QEMUBH version of the API
is removed.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-3-peter.maydell@linaro.org

Currently the ptimer design uses a QEMU bottom-half as its
mechanism for calling back into the device model using the
ptimer when the timer has expired. Unfortunately this design
is fatally flawed, because it means that there is a lag
between the ptimer updating its own state and the device
callback function updating device state, and guest accesses
to device registers between the two can return inconsistent
device state.

We want to replace the bottom-half design with one where
the guest device's callback is called either immediately
(when the ptimer triggers by timeout) or when the device
model code closes a transaction-begin/end section (when the
ptimer triggers because the device model changed the
ptimer's count value or other state). As the first step,
rename ptimer_init() to ptimer_init_with_bh(), to free up
the ptimer_init() name for the new API. We can then convert
all the ptimer users away from ptimer_init_with_bh() before
removing it entirely.

(Commit created with
 git grep -l ptimer_init | xargs sed -i -e 's/ptimer_init/ptimer_init_with_bh/'
and three overlong lines folded by hand.)
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20191008171740.9679-2-peter.maydell@linaro.org

Host kernel within [4.18, 5.3] report an erroneous KVM_MAX_VCPUS=512
for ARM. The actual capability to instantiate more than 256 vcpus
was fixed in 5.4 with the upgrade of the KVM_IRQ_LINE ABI to support
vcpu id encoded on 12 bits instead of 8 and a redistributor consuming
a single KVM IO device instead of 2.

So let's check this capability when attempting to use more than 256
vcpus within any ARM kvm accelerated machine.
Signed-off-by: NEric Auger <eric.auger@redhat.com>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Reviewed-by: NAndrew Jones <drjones@redhat.com>
Acked-by: NMarc Zyngier <maz@kernel.org>
Message-id: 20191003154640.22451-4-eric.auger@redhat.com
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

Host kernels that expose the KVM_CAP_ARM_IRQ_LINE_LAYOUT_2 capability
allow injection of interrupts along with vcpu ids larger than 255.
Let's encode the vpcu id on 12 bits according to the upgraded KVM_IRQ_LINE
ABI when needed.

Given that we have two callsites that need to assemble
the value for kvm_set_irq(), a new helper routine, kvm_arm_set_irq
is introduced.

Without that patch qemu exits with "kvm_set_irq: Invalid argument"
message.
Signed-off-by: NEric Auger <eric.auger@redhat.com>
Reported-by: NZenghui Yu <yuzenghui@huawei.com>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Reviewed-by: NAndrew Jones <drjones@redhat.com>
Acked-by: NMarc Zyngier <maz@kernel.org>
Message-id: 20191003154640.22451-3-eric.auger@redhat.com
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

Update the headers against commit:
0f1a7b3fac05 ("timer-of: don't use conditional expression
with mixed 'void' types")
Signed-off-by: NEric Auger <eric.auger@redhat.com>
Acked-by: NMarc Zyngier <maz@kernel.org>
Message-id: 20191003154640.22451-2-eric.auger@redhat.com
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

Block layer patches:

- block: Fix crash with qcow2 partial cluster COW with small cluster
  sizes (misaligned write requests with BDRV_REQ_NO_FALLBACK)
- qcow2: Fix integer overflow potentially causing corruption with huge
  requests
- vhdx: Detect truncated image files
- tools: Support help options for --object
- Various block-related replay improvements
- iotests/028: Fix for long $TEST_DIRs

# gpg: Signature made Mon 14 Oct 2019 17:02:54 BST
# gpg:                using RSA key 7F09B272C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>" [full]
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream:
  iotests: Test large write request to qcow2 file
  qcow2: Limit total allocation range to INT_MAX
  qemu-nbd: Support help options for --object
  qemu-img: Support help options for --object
  qemu-io: Support help options for --object
  vl: Split off user_creatable_print_help()
  iotests/028: Fix for long $TEST_DIRs
  block: Reject misaligned write requests with BDRV_REQ_NO_FALLBACK
  replay: add BH oneshot event for block layer
  replay: finish record/replay before closing the disks
  replay: don't drain/flush bdrv queue while RR is working
  replay: update docs for record/replay with block devices
  replay: disable default snapshot for record/replay
  block: implement bdrv_snapshot_goto for blkreplay
  block/vhdx: add check for truncated image files
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

Pull request

v2:
 * Replaced "Launchpad:" tag with "Buglink:" as documented on the SubmitAPatch wiki page [Philippe]

# gpg: Signature made Tue 15 Oct 2019 09:49:05 BST
# gpg:                using RSA key 8695A8BFD3F97CDAAC35775A9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/tracing-pull-request:
  trace: avoid "is" with a literal Python 3.8 warnings
  trace: add --group=all to tracing.txt
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

Pull request

# gpg: Signature made Mon 14 Oct 2019 09:52:03 BST
# gpg:                using RSA key 8695A8BFD3F97CDAAC35775A9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/block-pull-request:
  test-bdrv-drain: fix iothread_join() hang
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

The following statement produces a SyntaxWarning with Python 3.8:

  if len(format) is 0:
  scripts/tracetool/__init__.py:459: SyntaxWarning: "is" with a literal. Did you mean "=="?

Use the conventional len(x) == 0 syntax instead.
Reported-by: NDaniel P. Berrangé <berrange@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20191010122154.10553-1-stefanha@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

tracetool needs to know the group name ("all", "root", or a specific
subdirectory).  Also remove the stdin redirection because tracetool.py
needs the path to the trace-events file.  Update the documentation.

Fixes: 2098c56a
       ("trace: move setting of group name into Makefiles")
Buglink: https://bugs.launchpad.net/bugs/1844814Reported-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20191009135154.10970-1-stefanha@redhat.com>

qemu-openbios queue

# gpg: Signature made Sat 12 Oct 2019 10:47:55 BST
# gpg:                using RSA key CC621AB98E82200D915CC9C45BC2C56FAE0F321F
# gpg:                issuer "mark.cave-ayland@ilande.co.uk"
# gpg: Good signature from "Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>" [full]
# Primary key fingerprint: CC62 1AB9 8E82 200D 915C  C9C4 5BC2 C56F AE0F 321F

* remotes/mcayland/tags/qemu-openbios-20191012:
  Update OpenBIOS images to f28e16f9 built from submodule.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

Without HEAD^, the following happens when you attempt a large write
request to a qcow2 file such that the number of bytes covered by all
clusters involved in a single allocation will exceed INT_MAX:

(A) handle_alloc_space() decides to fill the whole area with zeroes and
    fails because bdrv_co_pwrite_zeroes() fails (the request is too
    large).

(B) If handle_alloc_space() does not do anything, but merge_cow()
    decides that the requests can be merged, it will create a too long
    IOV that later cannot be written.

(C) Otherwise, all parts will be written separately, so those requests
    will work.

In either B or C, though, qcow2_alloc_cluster_link_l2() will have an
overflow: We use an int (i) to iterate over nb_clusters, and then
calculate the L2 entry based on "i << s->cluster_bits" -- which will
overflow if the range covers more than INT_MAX bytes.  This then leads
to image corruption because the L2 entry will be wrong (it will be
recognized as a compressed cluster).

Even if that were not the case, the .cow_end area would be empty
(because handle_alloc() will cap avail_bytes and nb_bytes at INT_MAX, so
their difference (which is the .cow_end size) will be 0).

So this test checks that on such large requests, the image will not be
corrupted.  Unfortunately, we cannot check whether COW will be handled
correctly, because that data is discarded when it is written to null-co
(but we have to use null-co, because writing 2 GB of data in a test is
not quite reasonable).
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>