The Big QEMU Lock (BQL) has many names and they are confusing. The
actual QemuMutex variable is called qemu_global_mutex but it's commonly
referred to as the BQL in discussions and some code comments. The
locking APIs, however, are called qemu_mutex_lock_iothread() and
qemu_mutex_unlock_iothread().
The "iothread" name is historic and comes from when the main thread was
split into into KVM vcpu threads and the "iothread" (now called the main
loop thread). I have contributed to the confusion myself by introducing
a separate --object iothread, a separate concept unrelated to the BQL.
The "iothread" name is no longer appropriate for the BQL. Rename the
locking APIs to:
- void bql_lock(void)
- void bql_unlock(void)
- bool bql_locked(void)
There are more APIs with "iothread" in their names. Subsequent patches
will rename them. There are also comments and documentation that will be
updated in later patches.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paul Durrant <paul@xen.org>
Acked-by: Fabiano Rosas <farosas@suse.de>
Acked-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Acked-by: Peter Xu <peterx@redhat.com>
Acked-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Acked-by: Hyman Huang <yong.huang@smartx.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Message-id: 20240102153529.486531-2-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Figuring out why replay has failed is tricky at the best of times.
Lets centralise the reporting of a replay sync error and add a little
bit of extra information to help with debugging.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20231211091346.14616-10-alex.bennee@linaro.org>
For clarity given it only has two states.
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20231211091346.14616-9-alex.bennee@linaro.org>
Record/replay provides REPLAY_CLOCK_LOCKED macro to access
the clock when vm_clock_seqlock is locked. This macro is
needed because replay internals operate icount. In locked case
replay use icount_get_raw_locked for icount request, which prevents
excess locking which leads to deadlock. But previously only
record code used *_locked function and replay did not.
Therefore sometimes clock access lead to deadlocks.
This patch fixes clock access for replay too and uses *_locked
icount access function.
Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
Message-Id: <161347990483.1313189.8371838968343494161.stgit@pasha-ThinkPad-X280>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In record/replay icount mode main loop thread and vCPU thread
do not perform simultaneously. They take replay mutex to synchronize
the actions. Sometimes vCPU thread waits for locking the mutex for
very long time, because main loop releases the mutex and takes it
back again. Standard qemu mutex do not provide the ordering
capabilities.
This patch adds a "queue" for replay mutex. Therefore thread ordering
becomes more "fair". Threads are executed in the same order as
they are trying to take the mutex.
Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
Message-Id: <158823802979.28101.9340462887738957616.stgit@pasha-ThinkPad-X280>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This patch renames replay_get_current_step() and related variables
to make these names consistent with existing 'icount' command line
option and future record/replay hmp/qmp commands.
Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
Message-Id: <156404428377.18669.15476429889039912070.stgit@pasha-Precision-3630-Tower>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This is a fix which was missed by patch
74c0b816ad, which added current_step
parameter to the replay_advance_current_step function.
Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
Message-Id: <156404425561.18669.13015037579222450241.stgit@pasha-Precision-3630-Tower>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
sysemu/sysemu.h is a rather unfocused dumping ground for stuff related
to the system-emulator. Evidence:
* It's included widely: in my "build everything" tree, changing
sysemu/sysemu.h still triggers a recompile of some 1100 out of 6600
objects (not counting tests and objects that don't depend on
qemu/osdep.h, down from 5400 due to the previous two commits).
* It pulls in more than a dozen additional headers.
Split stuff related to run state management into its own header
sysemu/runstate.h.
Touching sysemu/sysemu.h now recompiles some 850 objects. qemu/uuid.h
also drops from 1100 to 850, and qapi/qapi-types-run-state.h from 4400
to 4200. Touching new sysemu/runstate.h recompiles some 500 objects.
Since I'm touching MAINTAINERS to add sysemu/runstate.h anyway, also
add qemu/main-loop.h.
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20190812052359.30071-30-armbru@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
[Unbreak OS-X build]
In my "build everything" tree, changing qemu/main-loop.h triggers a
recompile of some 5600 out of 6600 objects (not counting tests and
objects that don't depend on qemu/osdep.h). It includes block/aio.h,
which in turn includes qemu/event_notifier.h, qemu/notify.h,
qemu/processor.h, qemu/qsp.h, qemu/queue.h, qemu/thread-posix.h,
qemu/thread.h, qemu/timer.h, and a few more.
Include qemu/main-loop.h only where it's needed. Touching it now
recompiles only some 1700 objects. For block/aio.h and
qemu/event_notifier.h, these numbers drop from 5600 to 2800. For the
others, they shrink only slightly.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20190812052359.30071-21-armbru@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
No header includes qemu-common.h after this commit, as prescribed by
qemu-common.h's file comment.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20190523143508.25387-5-armbru@redhat.com>
[Rebased with conflicts resolved automatically, except for
include/hw/arm/xlnx-zynqmp.h hw/arm/nrf51_soc.c hw/arm/msf2-soc.c
block/qcow2-refcount.c block/qcow2-cluster.c block/qcow2-cache.c
target/arm/cpu.h target/lm32/cpu.h target/m68k/cpu.h target/mips/cpu.h
target/moxie/cpu.h target/nios2/cpu.h target/openrisc/cpu.h
target/riscv/cpu.h target/tilegx/cpu.h target/tricore/cpu.h
target/unicore32/cpu.h target/xtensa/cpu.h; bsd-user/main.c and
net/tap-bsd.c fixed up]
Currently replay_get_byte() does not check for an error
from getc(). Coverity points out (CID 1390622) that this
could result in unexpected behaviour (such as looping
forever, if we use the replay_get_dword() return value
for a loop count). We don't expect reads from the replay
log to fail, and if they do there is no way we can
continue. So make them fatal errors.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-id: 20181106153330.5139-1-peter.maydell@linaro.org
This patch adds error reporting when fwrite cannot completely
save the buffer to the file.
Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20180227095259.1060.86410.stgit@pasha-VirtualBox>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
Replay mutex is held by vCPU thread and destroy function is called
from atexit of the main thread. Therefore we cannot destroy it safely.
Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20180227095254.1060.96971.stgit@pasha-VirtualBox>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
The replay_mutex_lock/unlock/locked functions are now going to be used
for ensuring lock-step behaviour between the two threads. Make them
public API functions and also provide stubs for non-QEMU builds on
common paths.
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20180227095242.1060.16601.stgit@pasha-VirtualBox>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This is modelled after the iothread mutex lock. We keep a TLS flag to
indicate when that thread has acquired the lock and assert we don't
double-lock or release when we shouldn't have.
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20180227095237.1060.44661.stgit@pasha-VirtualBox>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
If we find ourselves trying to add an event to the log where time has
gone backwards it is because a vCPU event has occurred and the
main-loop is not yet aware of time moving forward. This should not
happen and if it does its better to fail early than generate a log
that will have weird behaviour.
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
This patch moves replay static variables into the structure
to allow saving and loading them with savevm/loadvm.
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20160926080804.6992.87687.stgit@PASHA-ISP>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Clean up includes so that osdep.h is included first and headers
which it implies are not included manually.
This commit was created with scripts/clean-includes.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1454089805-5470-16-git-send-email-peter.maydell@linaro.org
This patch adds icount event to the replay subsystem. This event corresponds
to execution of several instructions and used to synchronize input events
in the replay phase.
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20150917162354.8676.31351.stgit@PASHA-ISP.def.inno>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This mutex will protect read/write operations for replay log.
Using mutex is necessary because most of the events consist of
several fields stored in the log. The mutex will help to avoid races.
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20150917162348.8676.8628.stgit@PASHA-ISP.def.inno>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This patch adds functions to perform read and write operations
with replay log.
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20150917162342.8676.29445.stgit@PASHA-ISP.def.inno>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
