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X-Received-From: 2a00:1450:4864:20::32c Subject: [Qemu-devel] [PULL 16/48] vl: improve/fix documentation related to RTC function X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Artem Pisarenko Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZohoMail: RDMRC_1 RDKM_2 RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" From: Artem Pisarenko Documentation describing -rtc option updated to better match current implementation and highlight some important specifics. Signed-off-by: Artem Pisarenko Message-Id: <1b245c6c0803d4bf11dcbf9eb32f34af8c2bd0b4.1539846575.git.artem.= k.pisarenko@gmail.com> Signed-off-by: Paolo Bonzini --- 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) =20 DEF("rtc", HAS_ARG, QEMU_OPTION_rtc, \ - "-rtc [base=3Dutc|localtime|date][,clock=3Dhost|rt|vm][,driftfix=3Dnon= e|slew]\n" \ + "-rtc [base=3Dutc|localtime|][,clock=3Dhost|rt|vm][,driftfix= =3Dnone|slew]\n" \ " set the RTC base and clock, enable drift fix for cloc= k ticks (x86 only)\n", QEMU_ARCH_ALL) =20 STEXI =20 -@item -rtc [base=3Dutc|localtime|@var{date}][,clock=3Dhost|vm][,driftfix= =3Dnone|slew] +@item -rtc [base=3Dutc|localtime|@var{datetime}][,clock=3Dhost|rt|vm][,dri= ftfix=3Dnone|slew] @findex -rtc Specify @option{base} as @code{utc} or @code{localtime} to let the RTC sta= rt 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{date= time} in the format @code{2006-06-17T16:01:21} or @code{2006-06-17}. The default base i= s UTC. =20 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{c= lock} -to @code{rt} instead. To even prevent it from progressing during suspensi= on, -you can set it to @code{vm}. +to @code{rt} instead, which provides a host monotonic clock if host suppor= t it. +To even prevent the RTC from progressing during suspension, you can set @o= ption{clock} +to @code{vm} (virtual clock). @samp{clock=3Dvm} 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. =20 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 --=20 1.8.3.1