On Tue, Apr 08, 2025, Paolo Bonzini wrote:
> On 4/4/25 21:38, Sean Christopherson wrote:
> > Now that KVM provides the to-be-updated routing entry, stop walking the
> > routing table to find that entry. KVM, via setup_routing_entry() and
> > sanity checked by kvm_get_msi_route(), disallows having a GSI configured
> > to trigger multiple MSIs, i.e. the for-loop can only process one entry.
> >
> > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> > ---
> > arch/x86/kvm/vmx/posted_intr.c | 100 +++++++++++----------------------
> > 1 file changed, 33 insertions(+), 67 deletions(-)
> >
> > diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
> > index 00818ca30ee0..786912cee3f8 100644
> > --- a/arch/x86/kvm/vmx/posted_intr.c
> > +++ b/arch/x86/kvm/vmx/posted_intr.c
> > @@ -268,78 +268,44 @@ int vmx_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,
> > unsigned int host_irq, uint32_t guest_irq,
> > struct kvm_kernel_irq_routing_entry *new)
> > {
> > - struct kvm_kernel_irq_routing_entry *e;
> > - struct kvm_irq_routing_table *irq_rt;
> > - bool enable_remapped_mode = true;
> > struct kvm_lapic_irq irq;
> > struct kvm_vcpu *vcpu;
> > struct vcpu_data vcpu_info;
> > - bool set = !!new;
> > - int idx, ret = 0;
> > if (!vmx_can_use_vtd_pi(kvm))
> > return 0;
> > - idx = srcu_read_lock(&kvm->irq_srcu);
> > - irq_rt = srcu_dereference(kvm->irq_routing, &kvm->irq_srcu);
> > - if (guest_irq >= irq_rt->nr_rt_entries ||
> > - hlist_empty(&irq_rt->map[guest_irq])) {
> > - pr_warn_once("no route for guest_irq %u/%u (broken user space?)\n",
> > - guest_irq, irq_rt->nr_rt_entries);
> > - goto out;
> > - }
> > -
> > - hlist_for_each_entry(e, &irq_rt->map[guest_irq], link) {
> > - if (e->type != KVM_IRQ_ROUTING_MSI)
> > - continue;
> > -
> > - WARN_ON_ONCE(new && memcmp(e, new, sizeof(*new)));
>
> Alternatively, if you want to keep patches 28/29 separate, you could add
> this WARN_ON_ONCE to avic.c in the exact same place after checking e->type
> -- not so much for asserting purposes, but more to document what's going on
> for the reviewer.
FWIW, AVIC already has the same WARN, they were both added by "KVM: x86: Pass new
routing entries and irqfd when updating IRTEs".
That said, I agree that squashing 28/29 is the way to go, especially since I didn't
isolate the changes for VMX (I've no idea why I did for SVM but not VMX).
