> -----Original Message----- > From: kvm-ppc-owner@xxxxxxxxxxxxxxx [mailto:kvm-ppc- > owner@xxxxxxxxxxxxxxx] On Behalf Of Alexander Graf > Sent: Tuesday, September 27, 2011 1:45 PM > To: Wood Scott-B07421 > Cc: Liu Yu-B13201; Wood Scott-B07421; kvm-ppc@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 5/5] KVM: PPC: booke: Improve timer register > emulation > > > On 27.09.2011, at 02:44, Scott Wood wrote: > > > On 09/24/2011 02:27 AM, Alexander Graf wrote: > >> I think I'm getting your point. So what we want is: > >> > >> in timer handler: > >> > >> set_bit(TSR_DIS, vcpu->arch.tsr); > >> kvm_make_request(KVM_REQ_PPC_TSR_UPDATE, vcpu); > >> kvm_vcpu_kick(vcpu); Still there can be a case where first request not handled and another event happens? Or we would like to pause till first request is handled by vcpu? Thanks -Bharat > >> > >> in vcpu entry code: > >> > >> if (vcpu->requests) > >> if (kvm_check_request(KVM_REQ_PPC_TSR_UPDATE, vcpu)) > >> kvmppc_update_tsr(vcpu); > >> > >> void kvmppc_update_tsr(struct kvm_vcpu *vcpu) { > >> if (vcpu->arch.tsr & TSR_DIS && > >> vcpu->arch.tcr & TCR_DIE) { > >> kvmppc_core_queue_dec(vcpu); > >> } > >> // XXX also implement dequeue! > >> } > > > > OK, this avoids the possibility for the guest to clear DIS/DIE after > > enqueue but before delivery (which in the current patch is dealt with > > by an extra check at delivery), and we only have to check one thing in > > the common nothing-requested case (even if more things use this > > mechanism, as long as we don't run out of bits). > > > > If we convert external IRQs to using this as well, and expand the > > timer case to include non-booke (maybe just use > > KVM_REQ_PENDING_TIMER?), we should be able to de-atomicize > > pending_exceptions (which should be a bigger win than de-atomicizing > arch.tsr). > > > >> case SPR_TSR: > >> vcpu->arch.tsr &= ~TSR_DIS; > >> kvmppc_update_tsr(vcpu); > > > > Well, we should probably replace TSR_DIS here with the actual value > > that the guest wrote. :-) > > Yes, and use the atomic operation. This is all just pseudo-code. > > I like the idea of moving pending_exceptions off of atomic. This really > is a private field that no other vcpu should have access to. We only have > to think hard about how to implement SET_INTERRUPT for another vcpu then. > But I think this could just be another kvm_make_request() type. > > > Alex > > -- > To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the > body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at > http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
