Dong, Eddie wrote:
After thinking for a little while, you are theoretically right.
In the current state, we could even be preempted between all
operations ;-) Maybe after avi's suggestion of moving the call to it
it will end up in a preempt safe region, but anyway, it's safer to
add the preempt markers here. I'll put it in next version, thanks
Well, you can't kvm_write_guest() with preemption enabled.
preempt notifiers to the rescue! We have a callout during preemption,
so you can just zero out a flag there, and when we're scheduled again
retry the whole thing.
The preemption issue is within following code which need to be done in a
short enough period.
+ 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.
--
error compiling committee.c: too many arguments to function
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