On Tue, Jan 09, 2024 at 05:15:33PM -0800, Sean Christopherson wrote: > Nullify the async #PF worker's local "apf" pointer immediately after the > point where the structure can be freed by the vCPU. The existing comment > is helpful, but easy to overlook as there is no associated code. > > Update the comment to clarify that it can be freed by as soon as the lock > is dropped, as "after this point" isn't strictly accurate, nor does it > help understand what prevents the structure from being freed earlier. > > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> Reviewed-by: Xu Yilun <yilun.xu@xxxxxxxxx> > --- > virt/kvm/async_pf.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c > index c3f4f351a2ae..1088c6628de9 100644 > --- a/virt/kvm/async_pf.c > +++ b/virt/kvm/async_pf.c > @@ -83,13 +83,14 @@ static void async_pf_execute(struct work_struct *work) > apf->vcpu = NULL; > spin_unlock(&vcpu->async_pf.lock); > > - if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first) > - kvm_arch_async_page_present_queued(vcpu); > - > /* > - * apf may be freed by kvm_check_async_pf_completion() after > - * this point > + * The apf struct may freed by kvm_check_async_pf_completion() as soon > + * as the lock is dropped. Nullify it to prevent improper usage. > */ > + apf = NULL; > + > + if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first) > + kvm_arch_async_page_present_queued(vcpu); > > trace_kvm_async_pf_completed(addr, cr2_or_gpa); > > -- > 2.43.0.472.g3155946c3a-goog >
