Messages in this thread | | | Date | Tue, 13 Nov 2007 16:47:50 +0200 | From | Avi Kivity <> | Subject | Re: [kvm-devel] [PATCH 2/3] kvmclock - the host part. |
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Glauber de Oliveira Costa wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Dong, Eddie escreveu: > >>> +static void kvm_write_guest_time(struct kvm_vcpu *vcpu) +{ >>> + struct timespec ts; >>> + int r; >>> + >>> + if (!vcpu->clock_gpa) >>> + return; >>> + >>> + /* Updates version to the next odd number, indicating >>> we're writing */ >>> + vcpu->hv_clock.version++; >>> + kvm_write_guest(vcpu->kvm, vcpu->clock_gpa, >>> &vcpu->hv_clock, PAGE_SIZE); >>> + >>> + kvm_get_msr(vcpu, MSR_IA32_TIME_STAMP_COUNTER, >>> + &vcpu->hv_clock.last_tsc); >>> + >>> + ktime_get_ts(&ts); >>> >> Do we need to disable preemption here? >> > 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.
-- error compiling committee.c: too many arguments to function
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