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

  • To: "Bruce Rogers" <BROGERS@xxxxxxxxxx>
  • From: "B Thomas" <bjthomas3@xxxxxxxxx>
  • Date: Wed, 21 Jun 2006 11:29:15 -0400
  • Cc: Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Wed, 21 Jun 2006 08:30:12 -0700
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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 ?

- 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 ?


On 6/20/06, Bruce Rogers <BROGERS@xxxxxxxxxx> wrote:
Attached please find a patch (against unstable tree) which provides
some localtime support for paravirtualized guests.  It is quite
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
time base to be used for xenolinux.  That support would require
changes to Linux (eg a Xen aware implementation of /dev/rtc & etc.),
should probably be based on a more flexible and thorough implementation
non-UTC guest time bases than what this patch provides.  Nevertheless,
this patch is functionaly equivalent to what is being done SLES 10's
implementation (but with SLES10 being based on testing tree), so I felt
should be submitted as is, with a more comprehensive approach

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
>> 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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