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Revert some patches from recent [PATCH v6] "Fixing record/replay and adding reverse debugging"

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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>
This commit is contained in:
Artem Pisarenko 2018-10-17 14:24:18 +06:00 • committed by Paolo Bonzini
parent 24f7973b67
commit 05ff8dc32f
4 changed files with 7 additions and 19 deletions
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2
util/qemu-timer.c
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@ -496,7 +496,6 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
switch (timer_list->clock->type) {
case QEMU_CLOCK_REALTIME:
case QEMU_CLOCK_VIRTUAL_EXT:
break;
default:
case QEMU_CLOCK_VIRTUAL:
@ -598,7 +597,6 @@ int64_t qemu_clock_get_ns(QEMUClockType type)
return get_clock();
default:
case QEMU_CLOCK_VIRTUAL:
case QEMU_CLOCK_VIRTUAL_EXT:
if (use_icount) {
return cpu_get_icount();
} else {