Re: [Xen-devel] [PATCH v3 04/13] x86/time.c: Scale host TSC in pvclock properly

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 31.12.15 at 04:03, <haozhong.zhang@xxxxxxxxx> wrote:
> This patch makes the pvclock return the scaled host TSC and
> corresponding scaling parameters to HVM domains if guest TSC is not
> emulated and TSC scaling is enabled.
> 
> Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
> ---
> Changes in v3:
>  (addressing Boris Ostrovsky's comments)
>  * No changes in fact. tsc_set_info() does not set d->arch.vtsc to 0
>    if host_tsc_is_safe() is not satisfied, so it is safe to use
>    d->arch.vtsc_to_ns here.
> 
>  xen/arch/x86/time.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
> index d83f068..b31634a 100644
> --- a/xen/arch/x86/time.c
> +++ b/xen/arch/x86/time.c
> @@ -815,10 +815,18 @@ static void __update_vcpu_system_time(struct vcpu *v, 
> int force)
>      }
>      else
>      {
> -        tsc_stamp = t->local_tsc_stamp;
> -
> -        _u.tsc_to_system_mul = t->tsc_scale.mul_frac;
> -        _u.tsc_shift         = (s8)t->tsc_scale.shift;
> +        if ( has_hvm_container_domain(d) && cpu_has_tsc_ratio )

For symmetry with patches 1 and 2 I'd expect !d->arch.vtsc to be
added here too.

> +        {
> +            tsc_stamp            = hvm_funcs.scale_tsc(v, 
> t->local_tsc_stamp);
> +            _u.tsc_to_system_mul = d->arch.vtsc_to_ns.mul_frac;
> +            _u.tsc_shift         = d->arch.vtsc_to_ns.shift;
> +        }
> +        else
> +        {
> +            tsc_stamp            = t->local_tsc_stamp;
> +            _u.tsc_to_system_mul = t->tsc_scale.mul_frac;
> +            _u.tsc_shift         = (s8)t->tsc_scale.shift;

The case has been pointless anyway, and you don't add a similar
one in the if() branch - please delete it.

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel