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Re: [Xen-devel] [PATCH] time-xen : Reset monotonic time when sync up tim

To: "Hang Du" <hdu@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] time-xen : Reset monotonic time when sync up time from dom0 to domU
From: "Jan Beulich" <JBeulich@xxxxxxxxxx>
Date: Tue, 12 Oct 2010 12:48:30 +0100
Cc: Saipu Liu <saliu@xxxxxxxxxxxx>, Shunli Yi <syi@xxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
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>>> On 12.10.10 at 12:19, "Du, Hang" <hdu@xxxxxxxxxxxx> wrote:
> Signed-off-by: Shunli Yi <shyi@xxxxxxxxxxxx>
> Signed-off-by: Hang Du <hdu@xxxxxxxxxxxx>
> When sync up time from dom0 to domU, the monotonic time should be reset or 
> domU cannot sync up backward time from dom0.

Without a better description of what you try to do and why there
is no is_initial_xendomain() check in this code despite talk being
about sync-ing into a single direction (admittedly the word "backward"
above is confusing me quite a bit), I would ask that this patch not be


> diff -urN a/arch/i386/kernel/time-xen.c   b/arch/i386/kernel/time-xen.c
> --- a/arch/i386/kernel/time-xen.c   2010-10-11 10:41:06.000000000 +0800
> +++ b/arch/i386/kernel/time-xen.c   2010-10-11 10:43:32.000000000 +0800
> @@ -715,6 +715,8 @@
>     }
>     if (shadow_tv_version != HYPERVISOR_shared_info->wc_version) {
> +        if (!independent_wallclock)
> +            monotonic_reset();
>         update_wallclock();
>         schedule_clock_was_set_work = 1;
>     }
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