lkml.org 
[lkml]   [2007]   [Nov]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRE: [kvm-devel] [PATCH 2/3] kvmclock - the host part.
Date
From
>> 
>> + kvm_get_msr(vcpu, MSR_IA32_TIME_STAMP_COUNTER,
>> + &vcpu->hv_clock.last_tsc);
>> +
>> + ktime_get_ts(&ts);
>> + vcpu->hv_clock.now_ns = ts.tv_nsec + (NSEC_PER_SEC *
>> (u64)ts.tv_sec); + vcpu->hv_clock.wc_sec = get_seconds();
>>
>> I am even thinking we have to disable interrupt between these lines,
>> otherwise guest wall clock may see backward time source when
>> calculating the delta TSC since last vcpu->hv_clock.now_ns update.
>>
>
> That's true. While we do need to handle vcpu migration and
> descheduling, the code sequence you note needs to be as atomic as
> possible.
>

Yes VCPU migration is another issue. Since the physical platform TSC is
totally different across migration, so we can't expose host TSC to
guest.
For KVM, it should be simple to just use guest_TSC (=HOST_TSC + offset).

thanks, eddie
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-11-14 01:45    [W:0.074 / U:1.668 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site