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qemu-options.hx: Fix minor issues in icount documentation 

The documentation for the icount documentation has some minor issues:
 * in a couple of places it says "sleep=on|off" when in the context of the
   sentence it means specifically "sleep=on"
 * the synopsis line for the documentation has drifted out of sync
   with the synopsis line in the DEF() macro (used for "-help" output)
 * the synopsis line in the DEF() macro is missing a "][" between
   the sleep= part and the rr= part
 * the synopsis line doesn't indicate that rrsnapshot is an optional
   part of the rr=mode,rrfile=filename subgrouping
 * we don't document that sleep=on can't be used with shift=auto
   or align=on
 * the rr option description had some minor grammar and formatting
   errors and was a bit terse
 * in commit f1f4b57e88 in 2015 the documentation of the sleep=
   suboption got added between the two paragraphs defining general
   behaviour of the icount option. This meant that the second
   paragraph talking about the behaviour of "this option" reads as
   if it's talking about sleep=on, when it's really describing -icount
   as a whole. The paragraph is better moved back up to above the
   sleep= section.
 * the summary text displayed in "-help" output didn't mention
   the record-and-replay part

Fix these errors.

Fixes: https://bugs.launchpad.net/qemu/+bug/1774412
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20201121213506.15599-1-peter.maydell@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
This commit is contained in:
Peter Maydell 2020-11-21 21:35:06 +00:00 committed by Laurent Vivier
parent 6f8ddc2a89
commit fa647905e6
1 changed files with 24 additions and 18 deletions
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42
qemu-options.hx
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@ -3958,30 +3958,34 @@ SRST
ERST
DEF("icount", HAS_ARG, QEMU_OPTION_icount, \
"-icount [shift=N|auto][,align=on|off][,sleep=on|off,rr=record|replay,rrfile=<filename>,rrsnapshot=<snapshot>]\n" \
"-icount [shift=N|auto][,align=on|off][,sleep=on|off][,rr=record|replay,rrfile=<filename>[,rrsnapshot=<snapshot>]]\n" \
" enable virtual instruction counter with 2^N clock ticks per\n" \
" instruction, enable aligning the host and virtual clocks\n" \
" or disable real time cpu sleeping\n", QEMU_ARCH_ALL)
" or disable real time cpu sleeping, and optionally enable\n" \
" record-and-replay mode\n", QEMU_ARCH_ALL)
SRST
``-icount [shift=N|auto][,rr=record|replay,rrfile=filename,rrsnapshot=snapshot]``
``-icount [shift=N|auto][,align=on|off][,sleep=on|off][,rr=record|replay,rrfile=filename[,rrsnapshot=snapshot]]``
Enable virtual instruction counter. The virtual cpu will execute one
instruction every 2^N ns of virtual time. If ``auto`` is specified
then the virtual cpu speed will be automatically adjusted to keep
virtual time within a few seconds of real time.
When the virtual cpu is sleeping, the virtual time will advance at
default speed unless ``sleep=on|off`` is specified. With
``sleep=on|off``, the virtual time will jump to the next timer
deadline instantly whenever the virtual cpu goes to sleep mode and
will not advance if no timer is enabled. This behavior give
deterministic execution times from the guest point of view.
Note that while this option can give deterministic behavior, it does
not provide cycle accurate emulation. Modern CPUs contain
superscalar out of order cores with complex cache hierarchies. The
number of instructions executed often has little or no correlation
with actual performance.
When the virtual cpu is sleeping, the virtual time will advance at
default speed unless ``sleep=on`` is specified. With
``sleep=on``, the virtual time will jump to the next timer
deadline instantly whenever the virtual cpu goes to sleep mode and
will not advance if no timer is enabled. This behavior gives
deterministic execution times from the guest point of view.
The default if icount is enabled is ``sleep=off``.
``sleep=on`` cannot be used together with either ``shift=auto``
or ``align=on``.
``align=on`` will activate the delay algorithm which will try to
synchronise the host clock and the virtual clock. The goal is to
have a guest running at the real frequency imposed by the shift
@ -3991,15 +3995,17 @@ SRST
``shift`` is ``auto``. Note: The sync algorithm will work for those
shift values for which the guest clock runs ahead of the host clock.
Typically this happens when the shift value is high (how high
depends on the host machine).
depends on the host machine). The default if icount is enabled
is ``align=off``.
When ``rr`` option is specified deterministic record/replay is
enabled. Replay log is written into filename file in record mode and
read from this file in replay mode.
Option rrsnapshot is used to create new vm snapshot named snapshot
at the start of execution recording. In replay mode this option is
used to load the initial VM state.
When the ``rr`` option is specified deterministic record/replay is
enabled. The ``rrfile=`` option must also be provided to
specify the path to the replay log. In record mode data is written
to this file, and in replay mode it is read back.
If the ``rrsnapshot`` option is given then it specifies a VM snapshot
name. In record mode, a new VM snapshot with the given name is created
at the start of execution recording. In replay mode this option
specifies the snapshot name used to load the initial VM state.
ERST
DEF("watchdog", HAS_ARG, QEMU_OPTION_watchdog, \