Re: [Xen-devel] [PATCH v10 10/11] viridian: add implementation of synthetic timers

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 19.03.19 at 16:22, <paul.durrant@xxxxxxxxxx> wrote:
> This patch introduces an implementation of the STIMER0-15_CONFIG/COUNT MSRs
> and hence a the first SynIC message source.
> 
> The new (and documented) 'stimer' viridian enlightenment group may be
> specified to enable this feature.
> 
> While in the neighbourhood, this patch adds a missing check for an
> attempt to write the time reference count MSR, which should result in an
> exception (but not be reported as an unimplemented MSR).
> 
> NOTE: It is necessary for correct operation that timer expiration and
>       message delivery time-stamping use the same time source as the guest.
>       The specification is ambiguous but testing with a Windows 10 1803
>       guest has shown that using the partition reference counter as a
>       source whilst the guest is using RDTSC and the reference tsc page
>       does not work correctly. Therefore the time_now() function is used.
>       This implements the algorithm for acquiring partition reference time
>       that is documented in the specifiction.
> 
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>



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