Re: [Xen-devel] [PATCH] x86/time: update TSC stamp on restore from deep C-state

[Jan Beulich <jbeulich@xxxxxxxx>]

On 15.01.2020 14:44, Roger Pau Monné wrote:
> On Wed, Jan 15, 2020 at 01:49:22PM +0100, Jan Beulich wrote:
>> What I'm then worried about is too
>> little progress observable by guests. The PV time protocol
>> ought to be fine in this regard (and consumers of raw TSC values
>> are on their own anyway), but wouldn't you need to update TSC
>> offsets of HVM guests in order to compensate for the elapsed
>> time?
> 
> That will be done when the HVM vCPU gets scheduled in as part of the
> update_vcpu_system_time call AFAICT. cstate_restore_tsc will always be
> called with the idle vCPU context, and hence there's always going to
> be a vCPU switch before scheduling anything else.

Which step would this be? All I see is a call to hvm_scale_tsc().
In time.c only tsc_set_info() calls hvm_set_tsc_offset().

Jan

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