Re: [Xen-devel] [PATCHl] localtime basis for paravirtualized guests

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 21 Jun 2006, at 16:29, B Thomas wrote:

> Hi,
>
>  Two quick comments/questions come to mind upon seeing this patch:
>
>  - it appears possible to set/reset the time offset multiple times 
> even while the domain is running. Am I misreading the patch ?  Is this 
> desirable ?
Yes you can. No it probably isn't desirable, but the higher-level tools 
only call the lower-level command during domain initialisation. If they 
did call it at other times, it'd be up to them to sync with running 
guests somehow.
>  - this is a different mechanism than the one used to set time offsets 
> for fully virtualized guests. At the lowest levels, this is probably 
> difficult to avoid.  Higher up, though, it would be nice if this type 
> of capability didn't look/act and be controlled differently.  The 
> differences between fully and para virtualized systems should 
> disappear the higher into the control logic you go.  Were you able to 
> give any thought on how to merge the models ?
The 'support' for full-virt guests is *only* a qemu patch right now. No 
tools integration at all. Integration would have to be in xend, as it 
is xend which kicks off the qemu-dm process for HVM guests. Setting the 
'timeoffset' based on the localtime config option wouldn't be very 
hard, and would unify that new option across PV and HVM guests. Patches 
welcome (and moving the logic to work out what the time offset should 
be from xc.c into xend itself would be nice).
 -- Keir


>  -b
>
>
>
> On 6/20/06, Bruce Rogers <BROGERS@xxxxxxxxxx> wrote:
> > some localtime support for paravirtualized guests.  It is quite
> > minimal
> > in its approach, satisfying the purposes of the paravirtualized
> > NetWare operating system as well as any others that expect the time
> > base to be provided in localtime.
> >
> > I should point out however that this by itself does not allow a
> > localtime
> > time base to be used for xenolinux.  That support would require
> > additional
> > changes to Linux (eg a Xen aware implementation of /dev/rtc & etc.),
> > and
> > should probably be based on a more flexible and thorough 
> > implementation
> > of
> > non-UTC guest time bases than what this patch provides.  Nevertheless,
> > this patch is functionaly equivalent to what is being done SLES 10's
> > Xen
> > implementation (but with SLES10 being based on testing tree), so I 
> > felt
> > it
> > should be submitted as is, with a more comprehensive approach
> > submitted
> > separately.
> >
> > Signed-off-by: Bruce Rogers < brogers@xxxxxxxxxx>
> >
> > - Bruce
> >
> > >>> On 4/5/2006 at 8:03 AM, in message
> > <268cbf4ac7bb43efa0994df4a124a19d@xxxxxxxxxxxx >, Keir Fraser
> > <Keir.Fraser@xxxxxxxxxxxx> wrote:
> >
> > > On 31 Mar 2006, at 21:22, Bruce Rogers wrote:
> > >
> > >> This patch allows the localtime parameter to be used for
> > >> para-virtualized guests.
> > >> Some paravirtualized guests may need to start with a local time
> > basis
> > >> instead of UTC.
> > >> This patch provides for that need.  Please review and apply.
> > >
> > > I've just checked in a patch to provide a clean wallclock update
> > > interface from common Xen code. Please re-send based on that patch.
> > > Your dom0_op implementation should modify d->time_offset_seconds
> > > directly and then call update_domain_wallclock_time(d).
> > >
> > > Apart from that, the time_offset_seconds field in dom0_op.h should 
> > be
> > > type int32_t (we don't use s32 in public headers).
> > >
> > >   -- Keir
> > >
> > >
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> >
> >
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