Alexander Graf <agraf@xxxxxxx> writes: > On 05.06.14 17:50, Aneesh Kumar K.V wrote: >> Alexander Graf <agraf@xxxxxxx> writes: >> >>> On 05.06.14 14:08, Aneesh Kumar K.V wrote: >>>> virtual time base register is a per VM, per cpu register that needs >>>> to be saved and restored on vm exit and entry. Writing to VTB is not >>>> allowed in the privileged mode. >>>> >>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> ....... >>>> break; >>>> diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c >>>> index 3565e775b61b..1bb16a59dcbc 100644 >>>> --- a/arch/powerpc/kvm/book3s_emulate.c >>>> +++ b/arch/powerpc/kvm/book3s_emulate.c >>>> @@ -577,6 +577,9 @@ int kvmppc_core_emulate_mfspr_pr(struct kvm_vcpu *vcpu, int sprn, ulong *spr_val >>>> */ >>>> *spr_val = vcpu->arch.spurr; >>>> break; >>>> + case SPRN_VTB: >>>> + *spr_val = vcpu->arch.vtb; >>> Doesn't this mean that vtb can be the same 2 when the guest reads it 2 >>> times in a row without getting preempted? >> >> But a mfspr will result in VM exit and that would make sure we >> update vcpu->arch.vtb with the correct value. > > We only call kvmppc_core_vcpu_put_pr() when we context switch away from > KVM, so it won't be updated, no? > > kvmppc_copy_from_svcpu is also called from VM exit path (book3s_interrupt.S) -aneesh -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
