Re: [Xen-devel] [PATCH 1/6] x86/pvh: fix TSC mode setup for PVH Dom0

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 09.10.18 at 11:42, <roger.pau@xxxxxxxxxx> wrote:
> A PVH Dom0 might use TSC scaling or other HVM specific TSC
> adjustments, so only short-circuit the TSC setup for a classic PV
> Dom0.

How that?

> --- a/xen/arch/x86/time.c
> +++ b/xen/arch/x86/time.c
> @@ -2125,7 +2125,7 @@ void tsc_set_info(struct domain *d,
>  {
>      ASSERT(!is_system_domain(d));
>  
> -    if ( is_hardware_domain(d) )
> +    if ( is_pv_domain(d) && is_hardware_domain(d) )

This code path is reachable only from arch_domain_create()
(setting defaults) and XEN_DOMCTL_settscinfo (which Dom0 can't
issue against itself). So either there's some important part missing
from the description, or I fail to see what use this change is. Hmm,
on a platform where host_tsc_is_safe() returns false the setting
of defaults would have an effect, but I think the description
should then say so, instead of giving the impression that the
functionality would become available in full.

Jan



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