[PATCH] ide: refuse WIN_READ_NATIVE_MAX on empty device

What is the highest addressable sector on an empty CD-ROM?  Nothing is
addressable so produce an error.

This patch prevents a divide-by-zero in ide_set_sector() since
s->sectors and s->heads would be 0.  Not to mention that a sector=-1
argument would be nonsense.

Note that WIN_READ_NATIVE_MAX can be triggered using hdparm -N 1024
/dev/cdrom.  The LBA bit will be set to 1 though, so the only easy way
to go down the ide_set_sector() CHS code path which divides by zero is
to comment out the s->select & 0x40 case for testing.

http://lists.gnu.org/archive/html/qemu-devel/2013-04/msg01076.html
usb-storage: Forward serial number to scsi-disk

usb-storage takes care to fetch the USB serial number from -drive
options, but it neglected to pass its own 'serial' property to the
scsi-disk it creates. With this patch, the 'serial' qdev property and
the 'serial' option in -drive behave the same and correctly apply the
serial number on both USB and SCSI level.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit 0c10d1fb724f1c65420310772d43c2e41f64a372)
block: fix I/O throttling accounting blind spot

I/O throttling relies on bdrv_acct_done() which is called when a request
completes.  This leaves a blind spot since we only charge for completed
requests, not submitted requests.

For example, if there is 1 operation remaining in this time slice the
guest could submit 3 operations and they will all be submitted
successfully since they don't actually get accounted for until they
complete.

Originally we probably thought this is okay since the requests will be
accounted when the time slice is extended.  In practice it causes
fluctuations since the guest can exceed its I/O limit and it will be
punished for this later on.

Account for I/O upon submission so that I/O limits are enforced
properly.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-By: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 2f343721f4a88fb462372967c9a46a5ab72e3294)
block: keep I/O throttling slice time constant

It is not necessary to adjust the slice time at runtime.  We already
extend the current slice in order to carry over accounting into the next
slice.  Changing the actual slice time value introduces oscillations.

The guest may experience large changes in throughput or IOPS from one
moment to the next when slice times are adjusted.

Reported-by: Benoît Canet <benoit@irqsave.net>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-By: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 51877705e98adc83a0271e84c28ee5ca8f6eed5f)
block: drop duplicated slice extension code

The current slice is extended when an I/O request exceeds the limit.
There is no need to extend the slice every time we check a request.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-By: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 52714c09d1b7858d1dd0e54d53c42ad6cf107726)
block: clean up I/O throttling wait_time code

The wait_time variable is in seconds.  Reflect this in a comment and use
NANOSECONDS_PER_SECOND instead of BLOCK_IO_SLICE_TIME * 10 (which
happens to have the right value).

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-By: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit b5c3d794c14ed1c63c426ada46c6a17143b98084)
qcow2: Return real error in qcow2_update_snapshot_refcount

This fixes the error message triggered by the following script:

    cat > /tmp/blkdebug.cfg <<EOF
    [inject-error]
    event = "cluster_free"
    errno = "28"
    immediately = "off"
    EOF

    $qemu_img create -f qcow2 test.qcow2 10G
    $qemu_img snapshot -c snap test.qcow2
    $qemu_img snapshot -d snap blkdebug:/tmp/blkdebug.cfg:test.qcow2

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit f4b8089ec3df1e46a92dffa4a96500b2e633be0b)
qcow2: Fix L1 write error handling in qcow2_update_snapshot_refcount

It ignored the error code, and at least the 'goto fail' is obvious
nonsense as it creates an endless loop (if the next attempt doesn't
magically succeed) and leaves the in-memory L1 table in big-endian
instead of converting it back.

In error cases, there's no point in writing an updated L1 table, so
skip this part for them.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 094e751448359417c712ed1395d151c79ccd2538)
[PATCH] main-loop: drop the BQL if the I/O appears to be spinning

The char-flow refactoring introduced a busy-wait that depended on
an action from the VCPU thread.  However, the VCPU thread could
never take that action because the busy-wait starved the VCPU thread
of the BQL because it never dropped the mutex while running select.

Paolo doesn't want to drop this optimization for fear that we will
stop detecting these busy waits.  I'm afraid to keep this optimization
even with the busy-wait fixed because I think a similar problem can
occur just with heavy I/O thread load manifesting itself as VCPU pauses.

As a compromise, introduce an artificial timeout after a thousand
iterations but print a rate limited warning when this happens.  This
let's us still detect when this condition occurs without it being
a fatal error.
Revert "[Patch] [Trivial] issuing help command under qemu monitor casues a crash"

This reverts commit 6a7cb341e99b108dc48988f6a159f8ce30ba6eea.

This issue has been fixed by qemu mainstream.
test-visitor-serialization: Fix some memory leaks

This patch fixes some of the memory leaks in test-visitor-serialization but not all of them.

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit 2bd01ac1e238c76e201ba21f314cec46437d2c5a)
linux-user: Don't omit comma for strace of rt_sigaction()

Pass the 'last' parameter of print_signal() through to
print_raw_param(); this fixes a problem where we weren't printing
the comma separator for strace of rt_sigaction() when the signal
was an unnamed (ie realtime) one:
  6856 rt_sigaction(230xf6fff870,0xf6fff8fc) = 0

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit abe20840166e6f04d3ab60f8d53a2ff5907bd942)
qstring: add qstring_get_length()

Long overdue.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit 54d49ac99227aff646ac940abfab3417f5cb1693)
Monitor: Make output buffer dynamic

Commit f628926bb423fa8a7e0b114511400ea9df38b76a changed monitor_flush()
to retry on qemu_chr_fe_write() errors. However, the Monitor's output
buffer can keep growing while the retry is not issued and this can
cause the buffer to overflow.

To reproduce this issue, just start qemu and type on the Monitor:

(qemu) ?

This will cause an assertion to trig.

To fix this problem this commit makes the Monitor buffer dynamic,
which means that it can grow as much as needed.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit e1f2641b5926d20f63d36f0de45206be774da8da)
hmp: human-monitor-command: stop using the Memory chardev driver

The Memory chardev driver was added because, as the Monitor's output
buffer was static, we needed a way to accumulate the output of an
HMP commmand when ran by human-monitor-command.

However, the Monitor's output buffer is now dynamic, so it's possible
for the human-monitor-command to use it instead of the Memory chardev
driver.

This commit does that change, but there are two important
observations about it:

 1. We need a way to signal to the Monitor that it shouldn't call
    chardev functions when flushing its output. This is done
    by adding a new flag to the Monitor object called skip_flush
	(which is set to true by qmp_human_monitor_command())

 2. The current code has buffered semantics: QMP clients will
    only see a command's output if it flushes its output with
	a new-line character. This commit changes this to unbuffered,
	which means that QMP clients will see a command's output
	whenever the command prints anything.

	I don't think this will matter in practice though, as I believe
	all HMP commands print the new-line character anyway.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit 48c043d0d1835c64b571c484a9f229fe6d220287)
chardev: drop the Memory chardev driver

It's not used anymore since the last commit.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit 4bf0bb8014ac2ac61b1004f5d92b2a4594d48017)
Merge branch 'qemu.dev.block.1' into qemu.dev

1. usb-storage: Forward serial number to scsi-disk
2. block: fix I/O throttling accounting blind spot
3. block: keep I/O throttling slice time constant
4. block: drop duplicated slice extension code
5. block: clean up I/O throttling wait_time code
6. qcow2: Return real error in qcow2_update_snapshot_refcount
7. qcow2: Return real error in qcow2_update_snapshot_refcount
qemu-char: eliminate busy waiting on can_read returning zero

The character backend refactoring introduced an undesirable busy wait.
The busy wait happens if can_read returns zero and there is data available
on the character device's file descriptor.  Then, the I/O watch will
fire continuously and, with TCG, the CPU thread will never run.

    1) Char backend asks front end if it can write
    2) Front end says no
    3) poll() finds the char backend's descriptor is available
    4) Goto (1)

What we really want is this (note that step 3 avoids the busy wait):

    1) Char backend asks front end if it can write
    2) Front end says no
    3) poll() goes on without char backend's descriptor
    4) Goto (1) until qemu_chr_accept_input() called

    5) Char backend asks front end if it can write
    6) Front end says yes
    7) poll() finds the char backend's descriptor is available
    8) Backend handler called

After this patch, the IOWatchPoll source and the watch source are
separated.  The IOWatchPoll is simply a hook that runs during the prepare
phase on each main loop iteration.  The hook adds/removes the actual
source depending on the return value from can_read.

A simple reproducer is

    qemu-system-i386 -serial mon:stdio

... followed by banging on the terminal as much as you can. :)  Without
this patch, emulation will hang.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1365177573-11817-1-git-send-email-pbonzini@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
(cherry picked from commit d185c094b404b4ff392b77d1244c0233da7d53bd)