Pavel Dovgalyuk <dovga...@ispras.ru> writes: > Guest Windows XP doesn't boot with these patches.
I'm guessing there is hardware attached to that machine? Did the asserts catch double locking? As I said there are still changes to be made to the hardware emulation that saves async events with the device data. But the real question is do you think that re-purposing replay_lock to give the sequential guarantees that the BQL used to is the right approach? > > Pavel Dovgalyuk > > >> -----Original Message----- >> From: Alex Bennée [mailto:alex.ben...@linaro.org] >> Sent: Friday, May 05, 2017 1:38 PM >> To: pbonz...@redhat.com; boost.li...@gmail.com; pavel.dovga...@ispras.ru >> Cc: c...@braap.org; qemu-devel@nongnu.org; Alex Bennée >> Subject: [RFC PATCH v1 0/9] BQL and Replay Lock changes >> >> Hi, >> >> This RFC does two principle things. It continues the push to reduce >> the BQL lock contention to a minimum by dropping the BQL for most of >> the run loop - eventually only holding it for timer processing and >> sleeping. The second part is an attempt to fix the breakage caused to >> record/replay by the previous work reducing the BQL in 2.9. >> >> The patch breakdown is as follows: >> >> - target/arm/arm-powertctl: drop BQL assertions >> >> This just fixes a bogus assert. The async work doesn't need BQL >> protection as it is all done in the context of the vCPU (meaning >> nothing else should be messing with it). However going forward we will >> need to audit all the async work calls to make sure they are fine to >> run outside of the BQL. >> >> - cpus: push BQL lock to qemu_*_wait_io_event >> - cpus: only take BQL for sleeping threads >> >> The BQL reduction is done in two stages, mainly to make bisection >> easier. >> >> - replay/replay-internal.c: track holding of replay_lock >> - replay: make locking visible outside replay code >> - replay: push replay_mutex_lock up the call tree >> >> There is still more work to do here but essentially replay_lock now >> replaces the BQL in keeping synchronisation between main-loop and the >> TCG thread - it is no longer a fine lock for the replay log but a >> gross lock that keeps batches of updates together. So far I have been >> testing with the simple testcase: >> >> ./arm-softmmu/qemu-system-arm -machine type=vexpress-a9 -m 1024 \ >> -display none -smp 1 -kernel ../images/vexpress-kernel.img \ >> -dtb ../images/vexpress-v2p-ca9.dtb \ >> -append "console=ttyAMA0" -serial mon:stdio \ >> -icount shift=7,rr=record,rrfile=replay.bin >> >> ..and that works fine. However more complex testing with more devices >> to exercise the async events code is needed here. One change that >> needs some careful care is we are now not dropping the replay_mutex >> lock between events. >> >> And finally: >> >> - scripts/qemu-gdb: add simple tcg lock status helper >> - util/qemu-thread-*: add qemu_lock, locked and unlock trace events >> - scripts/analyse-locks-simpletrace.py: script to analyse lock times >> >> These are helpers I wrote while debugging the locking. The GDB helper >> is fairly dump but does attempt to show where locks are held. The >> qemu-lock tracing is a little hacky but could prove useful in doing >> more detailed lock analysis. >> >> Any thoughts/comments? Does this seem like a reasonable direction to >> go? >> >> Alex Bennée (9): >> target/arm/arm-powertctl: drop BQL assertions >> cpus: push BQL lock to qemu_*_wait_io_event >> cpus: only take BQL for sleeping threads >> replay/replay-internal.c: track holding of replay_lock >> replay: make locking visible outside replay code >> replay: push replay_mutex_lock up the call tree >> scripts/qemu-gdb: add simple tcg lock status helper >> util/qemu-thread-*: add qemu_lock, locked and unlock trace events >> scripts/analyse-locks-simpletrace.py: script to analyse lock times >> >> cpus-common.c | 13 ++--- >> cpus.c | 57 ++++++++++++++++++--- >> docs/replay.txt | 19 +++++++ >> include/qemu/thread.h | 7 ++- >> include/sysemu/replay.h | 16 ++++++ >> kvm-all.c | 4 -- >> replay/replay-char.c | 21 +++----- >> replay/replay-events.c | 18 ++----- >> replay/replay-internal.c | 22 +++++++- >> replay/replay-internal.h | 5 +- >> replay/replay-time.c | 10 ++-- >> replay/replay.c | 40 +++++++-------- >> scripts/analyse-locks-simpletrace.py | 99 >> ++++++++++++++++++++++++++++++++++++ >> scripts/qemu-gdb.py | 3 +- >> scripts/qemugdb/tcg.py | 46 +++++++++++++++++ >> stubs/replay.c | 15 ++++++ >> target/arm/arm-powerctl.c | 8 --- >> target/i386/hax-all.c | 2 - >> util/main-loop.c | 23 +++++++-- >> util/qemu-thread-posix.c | 11 +++- >> util/trace-events | 5 ++ >> vl.c | 2 + >> 22 files changed, 353 insertions(+), 93 deletions(-) >> create mode 100755 scripts/analyse-locks-simpletrace.py >> create mode 100644 scripts/qemugdb/tcg.py >> >> -- >> 2.11.0 -- Alex Bennée
