Re: [Xen-devel] [PATCH] public/xen.h: update the comment explaining 'Wallclock time'

[Juergen Gross <jgross@xxxxxxxx>]

On 12.09.19 16:05, Paul Durrant wrote:
> Since commit 0629adfd80e "Actually set a HVM domain's time offset when it
> sets the RTC", the comment in the public header has been misleading, since
> it claims that wallclock time is only updated by control software.
> Moreover, the comments stating that wc_sec and wc_nsec are seconds and
> nanoseconds (respectively) in UTC since the Unix epoch are bogus. Their
> values are adjusted by the domain's time_offset_seconds value, which is
> updated by a guest write to the emulated RTC and hence the wallclock
> timezone is under guest control.
>
> This patch attempts to bring the comment in line with reality whilst
> keeping it reasonably short.
>
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> ---
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Julien Grall <julien.grall@xxxxxxx>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Cc: Tim Deegan <tim@xxxxxxx>
> Cc: Wei Liu <wl@xxxxxxx>
> ---
>   xen/include/public/xen.h | 13 +++++++++----
>   1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
> index cef65c38e7..2755c5ad54 100644
> --- a/xen/include/public/xen.h
> +++ b/xen/include/public/xen.h
> @@ -775,12 +775,17 @@ struct shared_info {
>       xen_ulong_t evtchn_mask[sizeof(xen_ulong_t) * 8];
>   
>       /*
> -     * Wallclock time: updated only by control software. Guests should base
> -     * their gettimeofday() syscall on this wallclock-base value.
> +     * Wallclock time: updated by control software or RTC emulation.
> +     * Guests should base their gettimeofday() syscall on this
> +     * wallclock-base value.
> +     * The valus of wc_sec and wc_nsec are offsets from the Unix epoch
s/valus/values/


Juergen

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