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Re: [Xen-devel] [PATCH] Move RTC from Qemu to HV

To: "Yang, Xiaowei" <xiaowei.yang@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Move RTC from Qemu to HV
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Wed, 27 Sep 2006 09:56:55 +0100
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On 27/9/06 09:16, "Yang, Xiaowei" <xiaowei.yang@xxxxxxxxx> wrote:

> Lastly, as for CMOS ram initialization, we have an alternative: Only
> move the first 10 bytes of time/interrupt related CMOS ram out of 128
> from Qemu to HV while still leaving the left in Qemu. Unfortunately how
> to initialize time is still a little tricky: as we still need configure
> option (like localtime) to fill in the space, it may be passed by
> xc_set_hvm_param (like for option apic) at startup.
> What do you think of it?

Xen has a view of UTC, kept up to date by domain0. There is also facility
already to set a per-domain offset from UTC (XEN_DOMCTL_settimeoffset). So
Xen is quite capable of setting all time fields itself.

As for the rest of the CMOS fields, I believe that they only contain some
basic info like boot order? This is only derived by qemu from command-line
switches -- we could make xend push down initialiser values instead. Maybe
only pushing implementation of time-related CMOS bytes[*] to Xen in the
first instance does make sense though...

 -- Keir

[*] That's more than 10 bytes though, right? There are status and control
registers at indexes 0xa-0xd?

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