On Tue, May 09, 2017 at 07:17:06PM +0200, Andrew Jones wrote: > On Sat, May 06, 2017 at 08:12:56PM +0200, Christoffer Dall wrote: > > On Wed, May 03, 2017 at 06:06:30PM +0200, Andrew Jones wrote: > > > VCPU requests that the receiver should handle should only be cleared > > > by the receiver. > > > > I cannot parse this sentence. > > I'll try again: > > VCPU requests should only be cleared by the receiving VCPUs. The only > exception is when a request is set as a side-effect. In these cases > the "requester" threads may clear the requests when it is sure the > receiving VCPUs do not need to see them. >
I can parse this, and I mostly understand this, except for the part about side-effects. > > > > > Not only does this properly implement the protocol, > > > but also avoids bugs where one VCPU clears another VCPU's request, > > > before the receiving VCPU has had a chance to see it. > > > > Is this an actual race we have currently or just something thay may > > happen later. Im' not sure. > > Since ARM is just learning to handle VCPU requests, then it's not a bug > now. Actually, I think I should state this protocol (what I wrote above) > in the document, and then I can just reference that here in this commit > message as the justification for change. That might solve the missing piece for me above, yes. > > > > > ARM VCPUs > > > currently only handle one request, EXIT, and handling it is achieved > > > by checking pause to see if the VCPU should sleep. > > > > This makes sense. So forget my comment on the previous patch about > > getting rid of the pause flag. > > Forgotten > > > > > > > > > Signed-off-by: Andrew Jones <[email protected]> > > > --- > > > arch/arm/kvm/arm.c | 10 ++++++++-- > > > 1 file changed, 8 insertions(+), 2 deletions(-) > > > > > > diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c > > > index 9174ed13135a..7be0d9b0c63a 100644 > > > --- a/arch/arm/kvm/arm.c > > > +++ b/arch/arm/kvm/arm.c > > > @@ -553,7 +553,6 @@ void kvm_arm_resume_vcpu(struct kvm_vcpu *vcpu) > > > { > > > struct swait_queue_head *wq = kvm_arch_vcpu_wq(vcpu); > > > > > > - kvm_clear_request(KVM_REQ_VCPU_EXIT, vcpu); > > > vcpu->arch.pause = false; > > > swake_up(wq); > > > } > > > @@ -625,7 +624,14 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, > > > struct kvm_run *run) > > > > > > update_vttbr(vcpu->kvm); > > > > > > - if (vcpu->arch.power_off || vcpu->arch.pause) > > > + if (kvm_request_pending(vcpu)) { > > > + if (kvm_check_request(KVM_REQ_VCPU_EXIT, vcpu)) { > > > + if (vcpu->arch.pause) > > > + vcpu_sleep(vcpu); > > > + } > > > > Can we factor out this bit to a separate function, > > kvm_handle_vcpu_requests() or something like that? > > Later patches make this look a bit better, but a function to bundle all > the request handling up sounds good too. Will do. > Thanks, -Christoffer _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
