Re: windows acpi time drift

[Avi Kivity <avi@qumranet.com>]

Anthony Liguori wrote:
> Avi Kivity wrote:
>>   The fourth is probably impossible from userspace (and very 
>> difficult in the kernel).
>
> What makes it impossible to do in userspace?  If you managed a 
> tsc_offset in userspace, you would of course need to adjust that 
> tsc_offset within the kernel for the particular PCPU that you were on.
>

In the kernel you can to tricks like local_irq_disable(); rdtsc(); 
ktime_get(); local_irq_enable() to get a sense where the tsc is.

Take a look at kvm_inject_pit_timer_irqs() and 
kvm_pit_timer_intr_post().  An attempt to have a accurate userspace pit 
needs to take into account what those functions do.  I believe it's 
doable, but will require careful design of the interface (which should 
be usable for rtc and hpet as well).

-- 
error compiling committee.c: too many arguments to function


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