On Thu, 7 Oct 2021 16:28:56 +0200 Laurent Vivier <lvivier@xxxxxxxxxx> wrote: > Commit 112665286d08 moved guest_exit() in the interrupt protected > area to avoid wrong context warning (or worse), but the tick counter > cannot be updated and the guest time is accounted to the system time. > > To fix the problem port to POWER the x86 fix > 160457140187 ("Defer vtime accounting 'til after IRQ handling"): > > "Defer the call to account guest time until after servicing any IRQ(s) > that happened in the guest or immediately after VM-Exit. Tick-based > accounting of vCPU time relies on PF_VCPU being set when the tick IRQ > handler runs, and IRQs are blocked throughout the main sequence of > vcpu_enter_guest(), including the call into vendor code to actually > enter and exit the guest." > > Fixes: 112665286d08 ("KVM: PPC: Book3S HV: Context tracking exit guest context before enabling irqs") > Cc: npiggin@xxxxxxxxx > Cc: <stable@xxxxxxxxxxxxxxx> # 5.12 > Signed-off-by: Laurent Vivier <lvivier@xxxxxxxxxx> > --- > > Notes: > v2: remove reference to commit 61bd0f66ff92 > cc stable 5.12 > add the same comment in the code as for x86 > Works for me. As you stated in your answer, someone can polish the code later on. Reviewed-by: Greg Kurz <groug@xxxxxxxx> > arch/powerpc/kvm/book3s_hv.c | 24 ++++++++++++++++++++---- > 1 file changed, 20 insertions(+), 4 deletions(-) > > diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c > index 2acb1c96cfaf..a694d1a8f6ce 100644 > --- a/arch/powerpc/kvm/book3s_hv.c > +++ b/arch/powerpc/kvm/book3s_hv.c > @@ -3695,6 +3695,8 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc) > > srcu_read_unlock(&vc->kvm->srcu, srcu_idx); > > + context_tracking_guest_exit(); > + > set_irq_happened(trap); > > spin_lock(&vc->lock); > @@ -3726,9 +3728,15 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc) > > kvmppc_set_host_core(pcpu); > > - guest_exit_irqoff(); > - > local_irq_enable(); > + /* > + * Wait until after servicing IRQs to account guest time so that any > + * ticks that occurred while running the guest are properly accounted > + * to the guest. Waiting until IRQs are enabled degrades the accuracy > + * of accounting via context tracking, but the loss of accuracy is > + * acceptable for all known use cases. > + */ > + vtime_account_guest_exit(); > > /* Let secondaries go back to the offline loop */ > for (i = 0; i < controlled_threads; ++i) { > @@ -4506,13 +4514,21 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit, > > srcu_read_unlock(&kvm->srcu, srcu_idx); > > + context_tracking_guest_exit(); > + > set_irq_happened(trap); > > kvmppc_set_host_core(pcpu); > > - guest_exit_irqoff(); > - > local_irq_enable(); > + /* > + * Wait until after servicing IRQs to account guest time so that any > + * ticks that occurred while running the guest are properly accounted > + * to the guest. Waiting until IRQs are enabled degrades the accuracy > + * of accounting via context tracking, but the loss of accuracy is > + * acceptable for all known use cases. > + */ > + vtime_account_guest_exit(); > > cpumask_clear_cpu(pcpu, &kvm->arch.cpu_in_guest); >