Commit Graph

31 Commits

Author SHA1 Message Date
Idan Horowitz
3f42906c9a qemu-timer: Skip empty timer lists before locking in qemu_clock_deadline_ns_all
This decreases qemu_clock_deadline_ns_all's share from 23.2% to 13% in a
profile of icount-enabled aarch64-softmmu.

Signed-off-by: Idan Horowitz <idan.horowitz@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220114004358.299534-2-idan.horowitz@gmail.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2022-06-21 09:24:34 -07:00
Markus Armbruster
b21e238037 Use g_new() & friends where that makes obvious sense
g_new(T, n) is neater than g_malloc(sizeof(T) * n).  It's also safer,
for two reasons.  One, it catches multiplication overflowing size_t.
Two, it returns T * rather than void *, which lets the compiler catch
more type errors.

This commit only touches allocations with size arguments of the form
sizeof(T).

Patch created mechanically with:

    $ spatch --in-place --sp-file scripts/coccinelle/use-g_new-etc.cocci \
	     --macro-file scripts/cocci-macro-file.h FILES...

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20220315144156.1595462-4-armbru@redhat.com>
Reviewed-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
2022-03-21 15:44:44 +01:00
Daniel Henrique Barboza
d522cb52e6 spapr: rollback 'unplug timeout' for CPU hotunplugs
The pseries machines introduced the concept of 'unplug timeout' for CPU
hotunplugs. The idea was to circunvent a deficiency in the pSeries
specification (PAPR), that currently does not define a proper way for
the hotunplug to fail. If the guest refuses to release the CPU (see [1]
for an example) there is no way for QEMU to detect the failure.

Further discussions about how to send a QAPI event to inform about the
hotunplug timeout [2] exposed problems that weren't predicted back when
the idea was developed. Other QEMU machines don't have any type of
hotunplug timeout mechanism for any device, e.g. ACPI based machines
have a way to make hotunplug errors visible to the hypervisor. This
would make this timeout mechanism exclusive to pSeries, which is not
ideal.

The real problem is that a QAPI event that reports hotunplug timeouts
puts the management layer (namely Libvirt) in a weird spot. We're not
telling that the hotunplug failed, because we can't be 100% sure of
that, and yet we're resetting the unplug state back, preventing any
DEVICE_DEL events to reach out in case the guest decides to release the
device. Libvirt would need to inspect the guest itself to see if the
device was released or not, otherwise the internal domain states will be
inconsistent.  Moreover, Libvirt already has an 'unplug timeout'
concept, and a QEMU side timeout would need to be juggled together with
the existing Libvirt timeout.

All this considered, this solution ended up creating more trouble than
it solved. This patch reverts the 3 commits that introduced the timeout
mechanism for CPU hotplugs in pSeries machines.

This reverts commit 4515a5f786
"qemu_timer.c: add timer_deadline_ms() helper"

This reverts commit d1c2e3ce3d
"spapr_drc.c: add hotunplug timeout for CPUs"

This reverts commit 51254ffb32
"spapr_drc.c: introduce unplug_timeout_timer"

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1911414
[2] https://lists.gnu.org/archive/html/qemu-devel/2021-03/msg04682.html

CC: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <20210401000437.131140-2-danielhb413@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
2021-04-12 12:27:14 +10:00
Peter Maydell
1941858448 ppc patch queue for 2021-03-10
Next batch of patches for the ppc target and machine types.  Includes:
  * Several cleanups for sm501 from Peter Maydell
  * An update to the SLOF guest firmware
  * Improved handling of hotplug failures in spapr, associated cleanups
    to the hotplug handling code
  * Several etsec fixes and cleanups from Bin Meng
  * Assorted other fixes and cleanups
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Merge remote-tracking branch 'remotes/dg-gitlab/tags/ppc-for-6.0-20210310' into staging

ppc patch queue for 2021-03-10

Next batch of patches for the ppc target and machine types.  Includes:
 * Several cleanups for sm501 from Peter Maydell
 * An update to the SLOF guest firmware
 * Improved handling of hotplug failures in spapr, associated cleanups
   to the hotplug handling code
 * Several etsec fixes and cleanups from Bin Meng
 * Assorted other fixes and cleanups

# gpg: Signature made Wed 10 Mar 2021 04:08:53 GMT
# gpg:                using RSA key 75F46586AE61A66CC44E87DC6C38CACA20D9B392
# gpg: Good signature from "David Gibson <david@gibson.dropbear.id.au>" [full]
# gpg:                 aka "David Gibson (Red Hat) <dgibson@redhat.com>" [full]
# gpg:                 aka "David Gibson (ozlabs.org) <dgibson@ozlabs.org>" [full]
# gpg:                 aka "David Gibson (kernel.org) <dwg@kernel.org>" [unknown]
# Primary key fingerprint: 75F4 6586 AE61 A66C C44E  87DC 6C38 CACA 20D9 B392

* remotes/dg-gitlab/tags/ppc-for-6.0-20210310:
  spapr.c: send QAPI event when memory hotunplug fails
  spapr.c: remove duplicated assert in spapr_memory_unplug_request()
  target/ppc: fix icount support on Book-e vms accessing SPRs
  qemu_timer.c: add timer_deadline_ms() helper
  spapr_pci.c: add 'unplug already in progress' message for PCI unplug
  spapr.c: add 'unplug already in progress' message for PHB unplug
  hw/ppc: e500: Add missing <ranges> in the eTSEC node
  hw/net: fsl_etsec: Fix build error when HEX_DUMP is on
  spapr_drc.c: use DRC reconfiguration to cleanup DIMM unplug state
  spapr_drc.c: add hotunplug timeout for CPUs
  spapr_drc.c: introduce unplug_timeout_timer
  target/ppc: Fix bcdsub. emulation when result overflows
  docs/system: Extend PPC section
  spapr: rename spapr_drc_detach() to spapr_drc_unplug_request()
  spapr_drc.c: use spapr_drc_release() in isolate_physical/set_unusable
  pseries: Update SLOF firmware image
  spapr_drc.c: do not call spapr_drc_detach() in drc_isolate_logical()
  hw/display/sm501: Inline template header into C file
  hw/display/sm501: Expand out macros in template header
  hw/display/sm501: Remove dead code for non-32-bit RGB surfaces

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2021-03-12 11:30:55 +00:00
Daniel Henrique Barboza
4515a5f786 qemu_timer.c: add timer_deadline_ms() helper
The pSeries machine is using QEMUTimer internals to return the timeout
in seconds for a timer object, in hw/ppc/spapr.c, function
spapr_drc_unplug_timeout_remaining_sec().

Create a helper in qemu-timer.c to retrieve the deadline for a QEMUTimer
object, in ms, to avoid exposing timer internals to the PPC code.

CC: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <20210301124133.23800-2-danielhb413@gmail.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
2021-03-10 09:07:09 +11:00
Chen Qun
d6eb39b554 qtest: delete superfluous inclusions of qtest.h
There are 23 files that include the "sysemu/qtest.h",
but they do not use any qtest functions.

Signed-off-by: Chen Qun <kuhn.chenqun@huawei.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20210226081414.205946-1-kuhn.chenqun@huawei.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
2021-03-09 06:03:53 +01:00
Claudio Fontana
430065dab0 cpus: prepare new CpusAccel cpu accelerator interface
The new interface starts unused, will start being used by the
next patches.

It provides methods for each accelerator to start a vcpu, kick a vcpu,
synchronize state, get cpu virtual clock and elapsed ticks.

In qemu_wait_io_event, make it clear that APC is used only for HAX
on Windows.

Signed-off-by: Claudio Fontana <cfontana@suse.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-10-05 16:41:22 +02:00
Claudio Fontana
8191d36841 icount: rename functions to be consistent with the module name
Signed-off-by: Claudio Fontana <cfontana@suse.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-10-05 16:41:22 +02:00
Claudio Fontana
740b175973 cpu-timers, icount: new modules
refactoring of cpus.c continues with cpu timer state extraction.

cpu-timers: responsible for the softmmu cpu timers state,
            including cpu clocks and ticks.

icount: counts the TCG instructions executed. As such it is specific to
the TCG accelerator. Therefore, it is built only under CONFIG_TCG.

One complication is due to qtest, which uses an icount field to warp time
as part of qtest (qtest_clock_warp).

In order to solve this problem, provide a separate counter for qtest.

This requires fixing assumptions scattered in the code that
qtest_enabled() implies icount_enabled(), checking each specific case.

Signed-off-by: Claudio Fontana <cfontana@suse.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
[remove redundant initialization with qemu_spice_init]
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
[fix lingering calls to icount_get]
Signed-off-by: Claudio Fontana <cfontana@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-10-05 16:41:22 +02:00
Stefan Hajnoczi
d73415a315 qemu/atomic.h: rename atomic_ to qatomic_
clang's C11 atomic_fetch_*() functions only take a C11 atomic type
pointer argument. QEMU uses direct types (int, etc) and this causes a
compiler error when a QEMU code calls these functions in a source file
that also included <stdatomic.h> via a system header file:

  $ CC=clang CXX=clang++ ./configure ... && make
  ../util/async.c:79:17: error: address argument to atomic operation must be a pointer to _Atomic type ('unsigned int *' invalid)

Avoid using atomic_*() names in QEMU's atomic.h since that namespace is
used by <stdatomic.h>. Prefix QEMU's APIs with 'q' so that atomic.h
and <stdatomic.h> can co-exist. I checked /usr/include on my machine and
searched GitHub for existing "qatomic_" users but there seem to be none.

This patch was generated using:

  $ git grep -h -o '\<atomic\(64\)\?_[a-z0-9_]\+' include/qemu/atomic.h | \
    sort -u >/tmp/changed_identifiers
  $ for identifier in $(</tmp/changed_identifiers); do
        sed -i "s%\<$identifier\>%q$identifier%g" \
            $(git grep -I -l "\<$identifier\>")
    done

I manually fixed line-wrap issues and misaligned rST tables.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20200923105646.47864-1-stefanha@redhat.com>
2020-09-23 16:07:44 +01:00
Philippe Mathieu-Daudé
3cf10b2946 util/qemu-timer: Fix typo in description
Remove the second 'and' introduced in commit e81f86790f ("qemu-timer:
avoid checkpoints for virtual clock timers in external subsystems").

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Li Qiang <liq3ea@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20200811151643.21293-3-philmd@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
2020-09-01 11:08:57 +02:00
Pavel Dovgalyuk
677a3baba4 replay: synchronize on every virtual timer callback
Sometimes virtual timer callbacks depend on order
of virtual timer processing and warping of virtual clock.
Therefore every callback should be logged to make replay deterministic.
This patch creates a checkpoint before every virtual timer callback.
With these checkpoints virtual timers processing and clock warping
events order is completely deterministic.

Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
Acked-by: Alex Bennée <alex.bennee@linaro.org>

--

v2:
  - remove mutex lock/unlock for virtual clock checkpoint since it is
    not process any asynchronous events (commit ca9759c2a9)
  - bump record/replay log file version
Message-Id: <159012932716.27256.8854065545365559921.stgit@pasha-ThinkPad-X280>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-06-26 06:45:30 -04:00
Daniel Brodsky
6e8a355de6 lockable: replaced locks with lock guard macros where appropriate
- ran regexp "qemu_mutex_lock\(.*\).*\n.*if" to find targets
- replaced result with QEMU_LOCK_GUARD if all unlocks at function end
- replaced result with WITH_QEMU_LOCK_GUARD if unlock not at end

Signed-off-by: Daniel Brodsky <dnbrdsky@gmail.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Message-id: 20200404042108.389635-3-dnbrdsky@gmail.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2020-05-04 16:07:43 +01:00
Stefan Hajnoczi
3284c3ddc4 lockable: add lock guards
This patch introduces two lock guard macros that automatically unlock a
lock object (QemuMutex and others):

  void f(void) {
      QEMU_LOCK_GUARD(&mutex);
      if (!may_fail()) {
          return; /* automatically unlocks mutex */
      }
      ...
  }

and:

  WITH_QEMU_LOCK_GUARD(&mutex) {
      if (!may_fail()) {
          return; /* automatically unlocks mutex */
      }
  }
  /* automatically unlocks mutex here */
  ...

Convert qemu-timer.c functions that benefit from these macros as an
example.  Manual qemu_mutex_lock/unlock() callers are left unmodified in
cases where clarity would not improve by switching to the macros.

Many other QemuMutex users remain in the codebase that might benefit
from lock guards.  Over time they can be converted, if that is
desirable.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
[Use QEMU_MAKE_LOCKABLE_NONNULL. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2020-03-17 15:18:45 +01:00
Frediano Ziglio
5bd3435442 qemu-timer: reuse MIN macro in qemu_timeout_ns_to_ms
Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20191023122652.2999-3-fziglio@redhat.com>
[lv: removed the two useless casts]
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
2019-10-24 20:10:18 +02:00
Pavel Dovgalyuk
dcb1578069 util/qemu-timer: refactor deadline calculation for external timers
icount-based record/replay uses qemu_clock_deadline_ns_all to measure
the period until vCPU may be interrupted.
This function takes in account the virtual timers, because they belong
to the virtual devices that may generate interrupt request or affect
the virtual machine state.
However, there are a subset of virtual timers, that are marked with
'external' flag. These do not change the virtual machine state and
only based on virtual clock. Calculating the deadling using the external
timers breaks the determinism, because they do not belong to the replayed
part of the virtual machine.
This patch fixes the deadline calculation for this case by adding
new parameter for skipping the external timers when it is needed.

Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>

--

v2 changes:
 - added new parameter for timer attribute mask
Message-Id: <156404426682.18669.17014100602930969222.stgit@pasha-Precision-3630-Tower>

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2019-08-20 17:26:21 +02:00
Dr. David Alan Gilbert
3c2d4c8aa6 timer: last, remove last bits of last
The reset notifiers kept a 'last' counter to notice jumps;
now that we've remove the notifier we don't need to keep 'last'.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20190724115823.4199-5-dgilbert@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2019-08-20 17:26:21 +02:00
Dr. David Alan Gilbert
4ea9a0e3db timer: Remove reset notifiers
Remove the reset notifer from the core qemu-timer code.
The only user was mc146818 and we've just remove it's use.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20190724115823.4199-3-dgilbert@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2019-08-20 17:26:20 +02:00
Markus Armbruster
d5938f29fe Clean up inclusion of sysemu/sysemu.h
In my "build everything" tree, changing sysemu/sysemu.h triggers a
recompile of some 5400 out of 6600 objects (not counting tests and
objects that don't depend on qemu/osdep.h).

Almost a third of its inclusions are actually superfluous.  Delete
them.  Downgrade two more to qapi/qapi-types-run-state.h, and move one
from char/serial.h to char/serial.c.

hw/semihosting/config.c, monitor/monitor.c, qdev-monitor.c, and
stubs/semihost.c define variables declared in sysemu/sysemu.h without
including it.  The compiler is cool with that, but include it anyway.

This doesn't reduce actual use much, as it's still included into
widely included headers.  The next commit will tackle that.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20190812052359.30071-27-armbru@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
2019-08-16 13:31:53 +02:00
Artem Pisarenko
e81f86790f qemu-timer: avoid checkpoints for virtual clock timers in external subsystems
Adds EXTERNAL attribute definition to qemu timers subsystem and assigns
it to virtual clock timers, used in slirp (ICMP IPv6) and ui (key queue).
Virtual clock processing in rr mode can use this attribute instead of a
separate clock type.

Fixes: 87f4fe7653
Fixes: 775a412bf8
Fixes: 9888091404
Signed-off-by: Artem Pisarenko <artem.k.pisarenko@gmail.com>
Message-Id: <e771f96ab94e86b54b9a783c974f2af3009fe5d1.1539764043.git.artem.k.pisarenko@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-10-19 13:44:03 +02:00
Artem Pisarenko
89a603a0c8 qemu-timer: introduce timer attributes
Attributes are simple flags, associated with individual timers for their
whole lifetime.  They intended to be used to mark individual timers for
special handling when they fire.

New/init functions family in timer interface updated and refactored (new
'attribute' argument added, timer_list replaced with timer_list_group+type
combinations, comments improved to avoid info duplication).  Also existing
aio interface extended with attribute-enabled variants of functions,
which create/initialize timers.

Signed-off-by: Artem Pisarenko <artem.k.pisarenko@gmail.com>
Message-Id: <f47b81dbce734e9806f9516eba8ca588e6321c2f.1539764043.git.artem.k.pisarenko@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-10-19 13:44:03 +02:00
Artem Pisarenko
05ff8dc32f Revert some patches from recent [PATCH v6] "Fixing record/replay and adding reverse debugging"
That patch series introduced new virtual clock type for use in external
subsystems. It breaks desired behavior in non-record/replay usage
scenarios due to a small change to existing behavior.  Processing of
virtual timers belonging to new clock type is kicked off to the main
loop, which makes these timers asynchronous with vCPU thread and,
in icount mode, with whole guest execution. This breaks expected
determinism in non-record/replay icount mode of emulation where these
"external subsystems" are isolated from the host (i.e. they are
external only to guest core, not to the entire emulation environment).

Example for slirp ("user" backend for network device):
User runs qemu in icount mode with rtc clock=vm without any external
communication interfaces but with "-netdev user,restrict=on". It expects
deterministic execution, because network services are emulated inside
qemu and isolated from host. There are no reasons to get reply from DHCP
server with different delay or something like that.

The next patches revert reimplements the same changes in a better way.
This reverts commit 87f4fe7653.
This reverts commit 775a412bf8.
This reverts commit 9888091404.

Signed-off-by: Artem Pisarenko <artem.k.pisarenko@gmail.com>
Message-Id: <18b1e7c8f155fe26976f91be06bde98eef6f8751.1539764043.git.artem.k.pisarenko@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-10-19 13:44:03 +02:00
Pavel Dovgalyuk
87f4fe7653 timer: introduce new virtual clock
Slirp and VNC modules use virtual clock for processing some events that
are related to the guest execution speed.
But virtual clock-related events are consideres to be deterministic and
are recorded/replayed by icount mechanism. But slirp and VNC lie outside
the recorded guest core (which includes CPU and peripherals).
Therefore slirp and VNC are external for the guest, but should work at
guest speed.
This patch introduces new virtual clock which can be used for external
subsystems for running timers that are synchronized with the guest.

Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
Message-Id: <20180912082002.3228.82417.stgit@pasha-VirtualBox>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-10-02 19:08:58 +02:00
Pavel Dovgalyuk
e4dab9449a timer: remove replay clock probe in deadline calculation
Ciro Santilli reported that commit a5ed352596
breaks the execution replay. It happens due to the probing the clock
for the new instances of iothread.
However, this probing was made in replay mode for the timer lists that
are empty.
This patch removes clock probing in replay mode.
It is an artifact of the old version with another thread model.

Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
Message-Id: <20180725121526.12867.17866.stgit@pasha-VirtualBox>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2018-07-30 14:00:11 +02:00
Pavel Dovgalyuk
4b930d264c replay: save prior value of the host clock
This patch adds saving/restoring of the host clock field 'last'.
It is used in host clock calculation and therefore clock may
become incorrect when using restored vmstate.

Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20180227095226.1060.50975.stgit@pasha-VirtualBox>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
2018-03-12 16:12:50 +01:00
Paolo Bonzini
6b8f0187a4 icount: process QEMU_CLOCK_VIRTUAL timers in vCPU thread
icount has become much slower after tcg_cpu_exec has stopped
using the BQL.  There is also a latent bug that is masked by
the slowness.

The slowness happens because every occurrence of a QEMU_CLOCK_VIRTUAL
timer now has to wake up the I/O thread and wait for it.  The rendez-vous
is mediated by the BQL QemuMutex:

- handle_icount_deadline wakes up the I/O thread with BQL taken
- the I/O thread wakes up and waits on the BQL
- the VCPU thread releases the BQL a little later
- the I/O thread raises an interrupt, which calls qemu_cpu_kick
- the VCPU thread notices the interrupt, takes the BQL to
  process it and waits on it

All this back and forth is extremely expensive, causing a 6 to 8-fold
slowdown when icount is turned on.

One may think that the issue is that the VCPU thread is too dependent
on the BQL, but then the latent bug comes in.  I first tried removing
the BQL completely from the x86 cpu_exec, only to see everything break.
The only way to fix it (and make everything slow again) was to add a dummy
BQL lock/unlock pair.

This is because in -icount mode you really have to process the events
before the CPU restarts executing the next instruction.  Therefore, this
series moves the processing of QEMU_CLOCK_VIRTUAL timers straight in
the vCPU thread when running in icount mode.

The required changes include:

- make the timer notification callback wake up TCG's single vCPU thread
  when run from another thread.  By using async_run_on_cpu, the callback
  can override all_cpu_threads_idle() when the CPU is halted.

- move handle_icount_deadline after qemu_tcg_wait_io_event, so that
  the timer notification callback is invoked after the dummy work item
  wakes up the vCPU thread

- make handle_icount_deadline run the timers instead of just waking the
  I/O thread.

- stop processing the timers in the main loop

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-03-14 13:51:34 +01:00
Paolo Bonzini
3f53bc61a4 cpus: define QEMUTimerListNotifyCB for QEMU system emulation
There is no change for now, because the callback just invokes
qemu_notify_event.

Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-03-14 13:28:29 +01:00
Paolo Bonzini
d2528bdc19 qemu-timer: do not include sysemu/cpus.h from util/qemu-timer.h
This dependency is the wrong way, and we will need util/qemu-timer.h from
sysemu/cpus.h in the next patch.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-03-14 13:28:18 +01:00
Paolo Bonzini
33bef0b994 qemu-timer: fix off-by-one
If the first timer is exactly at the current value of the clock, the
deadline is met and the timer should fire.  This fixes itself on the next
iteration of the loop without icount; with icount, however, execution
of instructions will stop exactly at the deadline and won't proceed.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-03-14 13:26:42 +01:00
Marc-André Lureau
e703dcbaee timer: use an inline function for free
Similarly to allocation, do it from an inline function. This allows
tests to only use the headers for allocation/free of timer.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
2017-03-01 00:09:28 +04:00
Paolo Bonzini
c2b38b277a block: move AioContext, QEMUTimer, main-loop to libqemuutil
AioContext is fairly self contained, the only dependency is QEMUTimer but
that in turn doesn't need anything else.  So move them out of block-obj-y
to avoid introducing a dependency from io/ to block-obj-y.

main-loop and its dependency iohandler also need to be moved, because
later in this series io/ will call iohandler_get_aio_context.

[Changed copyright "the QEMU team" to "other QEMU contributors" as
suggested by Daniel Berrange and agreed by Paolo.
--Stefan]

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 20170213135235.12274-2-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-02-21 11:14:07 +00:00