On Fri, Apr 29, 2022 at 11:21 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
> On Fri, Apr 29, 2022 at 7:12 PM Peter Gonda <pgonda@xxxxxxxxxx> wrote:
> > Sounds good. Instead of doing this prev_vcpu solution we could just
> > keep the 1st vcpu for source and target. I think this could work since
> > all the vcpu->mutex.dep_maps do not point to the same string.
> >
> > Lock:
> > bool acquired = false;
> > kvm_for_each_vcpu(...) {
> > if (mutex_lock_killable_nested(&vcpu->mutex, role)
> > goto out_unlock;
> > acquired = true;
> > if (acquired)
> > mutex_release(&vcpu->mutex, role)
> > }
>
> Almost:
>
> bool first = true;
> kvm_for_each_vcpu(...) {
> if (mutex_lock_killable_nested(&vcpu->mutex, role)
> goto out_unlock;
> if (first)
> ++role, first = false;
> else
> mutex_release(&vcpu->mutex, role);
> }
>
> and to unlock:
>
> bool first = true;
> kvm_for_each_vcpu(...) {
> if (first)
> first = false;
> else
> mutex_acquire(&vcpu->mutex, role);
> mutex_unlock(&vcpu->mutex);
> acquired = false;
> }
>
> because you cannot use the first vCPU's role again when locking.
Ah yes I missed that. I would suggest `role = SEV_NR_MIGRATION_ROLES`
or something else instead of role++ to avoid leaking this
implementation detail outside of the function signature / enum.
>
> Paolo
>
