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[Qemu-devel] [PULL 16/48] vl: improve/fix documentation related to RTC f
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 16/48] vl: improve/fix documentation related to RTC function |
Date: |
Thu, 18 Oct 2018 22:31:43 +0200 |
From: Artem Pisarenko <address@hidden>
Documentation describing -rtc option updated to better match current
implementation and highlight some important specifics.
Signed-off-by: Artem Pisarenko <address@hidden>
Message-Id: <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
qemu-options.hx | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/qemu-options.hx b/qemu-options.hx
index f139459..829ed81 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3458,25 +3458,29 @@ HXCOMM Silently ignored for compatibility
DEF("clock", HAS_ARG, QEMU_OPTION_clock, "", QEMU_ARCH_ALL)
DEF("rtc", HAS_ARG, QEMU_OPTION_rtc, \
- "-rtc [base=utc|localtime|date][,clock=host|rt|vm][,driftfix=none|slew]\n"
\
+ "-rtc
[base=utc|localtime|<datetime>][,clock=host|rt|vm][,driftfix=none|slew]\n" \
" set the RTC base and clock, enable drift fix for clock
ticks (x86 only)\n",
QEMU_ARCH_ALL)
STEXI
address@hidden -rtc
[base=utc|localtime|@var{date}][,clock=host|vm][,driftfix=none|slew]
address@hidden -rtc
[base=utc|localtime|@var{datetime}][,clock=host|rt|vm][,driftfix=none|slew]
@findex -rtc
Specify @option{base} as @code{utc} or @code{localtime} to let the RTC start
at the current
UTC or local time, respectively. @code{localtime} is required for correct date
in
-MS-DOS or Windows. To start at a specific point in time, provide @var{date} in
the
+MS-DOS or Windows. To start at a specific point in time, provide
@var{datetime} in the
format @code{2006-06-17T16:01:21} or @code{2006-06-17}. The default base is
UTC.
By default the RTC is driven by the host system time. This allows using of the
RTC as accurate reference clock inside the guest, specifically if the host
time is smoothly following an accurate external reference clock, e.g. via NTP.
If you want to isolate the guest time from the host, you can set @option{clock}
-to @code{rt} instead. To even prevent it from progressing during suspension,
-you can set it to @code{vm}.
+to @code{rt} instead, which provides a host monotonic clock if host support it.
+To even prevent the RTC from progressing during suspension, you can set
@option{clock}
+to @code{vm} (virtual clock). @samp{clock=vm} is recommended especially in
+icount mode in order to preserve determinism; however, note that in icount mode
+the speed of the virtual clock is variable and can in general differ from the
+host clock.
Enable @option{driftfix} (i386 targets only) if you experience time drift
problems,
specifically with Windows' ACPI HAL. This option will try to figure out how
--
1.8.3.1
- [Qemu-devel] [PULL 04/48] qemu-timer: avoid checkpoints for virtual clock timers in external subsystems, (continued)
- [Qemu-devel] [PULL 04/48] qemu-timer: avoid checkpoints for virtual clock timers in external subsystems, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 03/48] qemu-timer: introduce timer attributes, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 09/48] target-i386: add rtc 0x70 port as coalesced_pio, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 01/48] es1370: more fixes for ADC_FRAMEADR and ADC_FRAMECNT, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 06/48] target-i386: kvm: do not initialize padding fields, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 12/48] replay: don't process events at virtual clock checkpoint, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 07/48] linux-headers: update to 4.20-rc1, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 08/48] target-i386 : add coalesced_pio API, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 11/48] target-i386: add q35 0xcf8 port as coalesced_pio, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 13/48] i386/kvm: add support for Hyper-V IPI send, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 16/48] vl: improve/fix documentation related to RTC function,
Paolo Bonzini <=
- [Qemu-devel] [PULL 18/48] Fixes RTC bug with base datetime shifts in clock=vm, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 19/48] vl, qapi: offset calculation in RTC_CHANGE event reverted, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 20/48] call HotplugHandler->plug() as the last step in device realization, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 21/48] hw: edu: drop DO_UPCAST, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 25/48] hyperv_testdev: drop unnecessary includes, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 10/48] target-i386: add i440fx 0xcf8 port as coalesced_pio, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 17/48] vl: refactor -rtc option references, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 15/48] i386: hvf: Remove hvf_disabled, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 14/48] i386: hvf: Fix register refs if REX is present, Paolo Bonzini, 2018/10/18
- [Qemu-devel] [PULL 24/48] hyperv_testdev: refactor for better maintainability, Paolo Bonzini, 2018/10/18