This patch implements the read/write state machine.  Operations are
fully asynchronous and multiple operations may be active at any time.

Allocating writes lock tables to ensure metadata updates do not
interfere with each other.  If two allocating writes need to update the
same L2 table they will run sequentially.  If two allocating writes need
to update different L2 tables they will run in parallel.
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

This patch adds code to look up data cluster offsets in the image via
the L1/L2 tables.  The L2 tables are writethrough cached in memory for
performance (each read/write requires a lookup so it is essential to
cache the tables).

With cluster lookup code in place it is possible to implement
bdrv_is_allocated() to query the number of contiguous
allocated/unallocated clusters.
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

VM state change notifications are invoked from vm_start()/vm_stop().
Trace these state changes so we can reason about the state of the VM
from trace output.
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

Replace debug printf statements with tracepoints.
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

Replace debug printf statements with tracepoints.
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

Observing block layer aio readv/writev operations is useful for
debugging image formats or understanding guest disk I/O patterns.
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

It is not portable to use "%ld" for int64_t because int64_t may have
type long on 64-bit platforms and long long on 32-bit platforms.  Use
the standard library PRId64 macros to keep format strings portable.
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

There is no qemu_valloc() but qemu_vmalloc().
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

Signed-off-by: NPrerna Saxena <prerna@linux.vnet.ibm.com>
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>

Signed-off-by: NPrerna Saxena <prerna@linux.vnet.ibm.com>
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>

This patch adds trace events for virtqueue operations including
adding/removing buffers, notifying the guest, and receiving a notify
from the guest.
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>

This patch adds trace events that make it possible to observe
virtio-blk.
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>

It is often useful to instrument memory management functions in order to
find leaks or performance problems.  This patch adds trace events for
the memory allocation primitives.
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>

Sometimes it is useful to disable a trace event.  Removing the event
from trace-events is not enough since source code will call the
trace_*() function for the event.

This patch makes it easy to build without specific trace events by
marking them disabled in trace-events:

disable multiwrite_cb(void *mcb, int ret) "mcb %p ret %d"

This builds without the multiwrite_cb trace event.
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>

trace: Allow bulk enabling/disabling of trace events at compile time

For 'simple' trace backend, allow bulk enabling/disabling of trace
events at compile time.  Trace events that are preceded by 'disable'
keyword are compiled in, but turned off by default. These can
individually be turned on using the monitor.  All other trace events are
enabled by default.

TODO :
This could be enhanced when the trace-event namespace is partitioned into a
group and an ID within that group. In such a case, marking a group as enabled
would automatically enable all trace-events listed under it.
Signed-off-by: NPrerna Saxena <prerna@linux.vnet.ibm.com>
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>

This patch introduces the trace-events file where trace events can be
declared like so:

qemu_malloc(size_t size) "size %zu"
qemu_free(void *ptr) "ptr %p"

These trace event declarations are processed by a new tool called
tracetool to generate code for the trace events.  Trace event
declarations are independent of the backend tracing system (LTTng User
Space Tracing, ftrace markers, DTrace).

The default "nop" backend generates empty trace event functions.
Therefore trace events are disabled by default.

The trace-events file serves two purposes:

1. Adding trace events is easy.  It is not necessary to understand the
   details of a backend tracing system.  The trace-events file is a
   single location where trace events can be declared without code
   duplication.

2. QEMU is not tightly coupled to one particular backend tracing system.
   In order to support tracing across QEMU host platforms and to
   anticipate new backend tracing systems that are currently maturing,
   it is important to be flexible and not tied to one system.

This commit includes fixes from Prerna Saxena
<prerna@linux.vnet.ibm.com> and Blue Swirl <blauwirbel@gmail.com>.
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>