Re: xen-4.1: PV domain hanging at startup, jiffies stopped

[Keir Fraser <keir.xen@gmail.com>]

On 31/08/2011 22:13, "Marek Marczykowski" <marmarek@mimuw.edu.pl> wrote:

>> They really ought to work out to the same thing. This will trivially be the
>> case with tsc_mode=2 because both guest and hypervisor will see the same
>> (real) values from RDTSC, and use the same offsets and sacle factors to turn
>> that into a current system time. When using emulated TSC in the guest
>> (tsc_mode=0,1) then the TSC values it sees, and the offsets and scale
>> factors it applies, are different. It is intended that it should result in
>> the same values being computed for NOW(), but I suppose something could be
>> going wrong there.
> 
> NOW() calls get_s_time() which doesn't look to be depended on tsc_mode
> setting. Have I missed something?

I mean the result of xen_clocksource_read() in the guest kernel, which we
expect to match the result of executing NOW() in the hypervisor. The former
does depend on tsc_mode because xen_clocksource_read() uses RDTSC.

 -- Keir