From: Keir Fraser <keir@xen.org>
To: James Harper <james.harper@bendigoit.com.au>,
xen-devel@lists.xensource.com
Subject: Re: common time reference between domU and dom0
Date: Fri, 10 Dec 2010 10:45:08 +0000 [thread overview]
Message-ID: <C927B534.C5BA%keir@xen.org> (raw)
In-Reply-To: <AEC6C66638C05B468B556EA548C1A77D01BB8980@trantor>
On 10/12/2010 10:20, "James Harper" <james.harper@bendigoit.com.au> wrote:
>> On 10/12/2010 08:23, "James Harper" <james.harper@bendigoit.com.au>
> wrote:
>>
>>>>
>>>> System time, as exposed to guests by Xen, should be good enough.
>>>>
>>>
>>> How is this exposed for HVM systems?
>>
>> Given all HVM guest time sources are trapped to the hypervisor,
> including
>> TSC, you may as well just use the HVMOP_get_time hypercall.
>>
>
> Is that a new call? I don't see it mentioned in 4.0-testing anywhere.
Yeah I think it's in 4.1 only.
> Is there a fallback if HVMOP_get_time doesn't exist?
Switch on vtsc (might be default) and just use RDTSC? Might be good enough.
I'm not sure that computing system time yourself from fields in shared info
works well for HVM guests. HVMOP_get_time I think had been in XenServer
patch queue a while and has just been pulled across to upstream.
-- Keir
> James
>
next prev parent reply other threads:[~2010-12-10 10:45 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-10 5:23 common time reference between domU and dom0 James Harper
2010-12-10 7:19 ` Keir Fraser
2010-12-10 8:23 ` James Harper
2010-12-10 10:00 ` Keir Fraser
2010-12-10 10:20 ` James Harper
2010-12-10 10:22 ` Paolo Bonzini
2010-12-10 10:45 ` Keir Fraser
2010-12-10 20:27 ` Dan Magenheimer
2010-12-10 21:41 ` Paolo Bonzini
2010-12-10 10:45 ` Keir Fraser [this message]
2010-12-10 10:51 ` Tim Deegan
2010-12-10 20:24 ` Dan Magenheimer
2010-12-10 8:26 ` Henry Pepper
2010-12-10 10:03 ` Keir Fraser
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