[PATCH v4 08/48] KVM: arm64: gic-v5: Add VPE doorbell domain
Sascha Bischoff
Sascha.Bischoff at arm.com
Fri Jul 31 01:35:53 PDT 2026
On Sat, 2026-07-25 at 11:56 +0100, Marc Zyngier wrote:
> On Fri, 24 Jul 2026 11:50:28 +0100,
> Sascha Bischoff <Sascha.Bischoff at arm.com> wrote:
> >
> > VPE doorbells allow the GICv5 hardware to notify KVM when an SPI or
> > LPI
> > can be signalled to a non-resident VPE. This provides the mechanism
> > used
> > to wake blocked vcpus once the hardware determines that the
> > interrupt is
> > eligible to be delivered.
> >
> > Add support for a per-VM VPE doorbell irq domain. The domain is
> > created
> > under the GICv5 LPI domain, with one doorbell allocated per VPE.
> > Store
> > the allocated doorbell base in the VM's GICv5 state so that later
> > patches can request per-vcpu doorbell IRQs and use them for IRS
> > commands and wakeups.
> >
> > Add the per-VPE doorbell state to the GICv5 CPU interface state.
> > The
> > doorbell IRQ number is populated when the IRQs are requested, and
> > the
> > db_fired state is used by later patches once doorbell delivery is
> > wired
> > up.
> >
> > Signed-off-by: Sascha Bischoff <sascha.bischoff at arm.com>
> > ---
> > arch/arm64/kvm/vgic/vgic-init.c | 18 ++--
> > arch/arm64/kvm/vgic/vgic-v5.c | 139
> > +++++++++++++++++++++++++++++
> > arch/arm64/kvm/vgic/vgic.h | 1 +
> > include/kvm/arm_vgic.h | 4 +
> > include/linux/irqchip/arm-gic-v5.h | 2 +
> > 5 files changed, 158 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/arm64/kvm/vgic/vgic-init.c
> > b/arch/arm64/kvm/vgic/vgic-init.c
> > index 907057881b26a..625d352756fcf 100644
> > --- a/arch/arm64/kvm/vgic/vgic-init.c
> > +++ b/arch/arm64/kvm/vgic/vgic-init.c
> > @@ -492,16 +492,22 @@ static void kvm_vgic_dist_destroy(struct kvm
> > *kvm)
> > dist->nr_spis = 0;
> > dist->vgic_dist_base = VGIC_ADDR_UNDEF;
> >
> > - if (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3) {
> > + switch (dist->vgic_model) {
> > + case KVM_DEV_TYPE_ARM_VGIC_V2:
> > + dist->vgic_cpu_base = VGIC_ADDR_UNDEF;
> > + break;
> > + case KVM_DEV_TYPE_ARM_VGIC_V3:
> > list_for_each_entry_safe(rdreg, next, &dist-
> > >rd_regions, list)
> > vgic_v3_free_redist_region(kvm, rdreg);
> > INIT_LIST_HEAD(&dist->rd_regions);
> > - } else {
> > - dist->vgic_cpu_base = VGIC_ADDR_UNDEF;
> > - }
> >
> > - if (vgic_supports_direct_irqs(kvm))
> > - vgic_v4_teardown(kvm);
> > + if (vgic_supports_direct_irqs(kvm))
> > + vgic_v4_teardown(kvm);
> > + break;
> > + case KVM_DEV_TYPE_ARM_VGIC_V5:
> > + vgic_v5_teardown(kvm);
> > + break;
> > + }
> >
> > xa_destroy(&dist->lpi_xa);
> > }
> > diff --git a/arch/arm64/kvm/vgic/vgic-v5.c
> > b/arch/arm64/kvm/vgic/vgic-v5.c
> > index 3f7b132110114..ebd7c3ede975f 100644
> > --- a/arch/arm64/kvm/vgic/vgic-v5.c
> > +++ b/arch/arm64/kvm/vgic/vgic-v5.c
> > @@ -7,6 +7,7 @@
> >
> > #include <linux/bitops.h>
> > #include <linux/irqchip/arm-vgic-info.h>
> > +#include <linux/irqdomain.h>
> >
> > #include "vgic.h"
> >
> > @@ -152,6 +153,134 @@ int vgic_v5_probe(const struct gic_kvm_info
> > *info)
> > return 0;
> > }
> >
> > +/*
> > + * This set of irq_chip functions is specific for doorbells.
> > + */
> > +static const struct irq_chip vgic_v5_db_irq_chip = {
> > + .name = "GICv5-DB",
> > + .irq_mask = irq_chip_mask_parent,
> > + .irq_unmask = irq_chip_unmask_parent,
> > + .irq_eoi = irq_chip_eoi_parent,
> > + .irq_set_affinity = irq_chip_set_affinity_parent,
> > + .irq_get_irqchip_state = irq_chip_get_parent_state,
> > + .irq_set_irqchip_state = irq_chip_set_parent_state,
> > + .flags = IRQCHIP_SET_TYPE_MASKED | IRQCHIP_SKIP_SET_WAKE |
> > + IRQCHIP_MASK_ON_SUSPEND,
> > +};
> > +
> > +static void vgic_v5_irq_db_domain_free(struct irq_domain *domain,
> > + unsigned int virq, unsigned
> > int nr_irqs)
> > +{
> > + int i;
> > +
> > + for (i = 0; i < nr_irqs; i++) {
> > + struct irq_data *d =
> > irq_domain_get_irq_data(domain, virq + i);
> > +
> > + irq_set_handler(virq + i, NULL);
> > + irq_domain_reset_irq_data(d);
> > + }
> > +
> > + irq_domain_free_irqs_parent(domain, virq, nr_irqs);
> > +}
> > +
> > +static int vgic_v5_irq_db_domain_alloc(struct irq_domain *domain,
> > + unsigned int virq, unsigned
> > int nr_irqs,
> > + void *arg)
> > +{
> > + const struct irq_chip *chip = &vgic_v5_db_irq_chip;
> > + struct vgic_v5_vm *vm = arg;
> > + struct irq_data *irqd;
> > + int ret;
> > +
> > + if (!vm) {
> > + kvm_err("invalid parameter for doorbell irq
> > allocation\n");
> > + return -EINVAL;
> > + }
>
> How can this happen?
I don't think it realistically can. We can't make it this far without
that so the check is utterly pointless. I've dropped it.
>
> > +
> > + ret = irq_domain_alloc_irqs_parent(domain, virq, nr_irqs,
> > NULL);
> > + if (ret)
> > + return ret;
> > +
> > + for (int i = 0; i < nr_irqs; i++) {
> > + irq_domain_set_hwirq_and_chip(domain, virq + i, i,
> > chip,
> > + domain->host_data);
> > + irqd = irq_desc_get_irq_data(irq_to_desc(virq +
> > i));
> > + irqd_set_single_target(irqd);
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static const struct irq_domain_ops vgic_v5_irq_db_domain_ops = {
> > + .alloc = vgic_v5_irq_db_domain_alloc,
> > + .free = vgic_v5_irq_db_domain_free,
> > +};
> > +
> > +static int vgic_v5_create_per_vm_domain(struct kvm *kvm)
> > +{
> > + struct vgic_v5_vm *vm = &kvm->arch.vgic.gicv5_vm;
> > + int nr_vcpus = atomic_read(&kvm->online_vcpus);
> > + int id = task_pid_nr(current);
> > + int ret, db_virq = 0;
> > +
> > + if (!gicv5_global_data.lpi_domain) {
> > + kvm_err("LPI domain uninitialized, can't set up
> > KVM Doorbells\n");
> > + return -ENODEV;
> > + }
>
> Surely we should fail KVM's initialisation if we don't have the LPI
> domain, rather than checking this at the point of creating the
> doorbells. I can't imagine how we'd run on GICv5 without LPIs
> anyway...
I've moved this check to probe time. It might even make sense to skip
the registration with KVM in the host driver altogether, however.
>
> > +
> > + vm->fwnode = irq_domain_alloc_named_id_fwnode("GICv5-vpe-
> > db", id);
> > + if (!vm->fwnode)
> > + return -ENOMEM;
> > +
> > + /*
> > + * KVM per-VM VPE DB domain; child of LPI domain; only
> > ever handles
> > + * doorbells. We know how many doorbells we have, and
> > therefore we
> > + * create a linear domain.
>
> The linear domain thing is an irqdomain implementation detail. We
> don't need to capture this here.
OK, removed.
>
> > + */
> > + vm->domain =
> > irq_domain_create_hierarchy(gicv5_global_data.lpi_domain,
> > + 0, nr_vcpus, vm-
> > >fwnode,
> > +
> > &vgic_v5_irq_db_domain_ops, vm);
> > + if (!vm->domain) {
> > + ret = -ENOMEM;
> > + goto err;
> > + }
> > +
> > + db_virq = irq_domain_alloc_irqs(vm->domain, nr_vcpus,
> > NUMA_NO_NODE, vm);
> > + if (db_virq <= 0) {
> > + ret = db_virq;
> > + goto err;
> > + }
> > +
> > + kvm->arch.vgic.gicv5_vm.vpe_db_base = db_virq;
> > +
> > + return 0;
> > +
> > +err:
> > + if (db_virq > 0)
> > + irq_domain_free_irqs(db_virq, nr_vcpus);
> > + if (vm->domain)
> > + irq_domain_remove(vm->domain);
> > + if (vm->fwnode)
> > + irq_domain_free_fwnode(vm->fwnode);
> > +
> > + kvm->arch.vgic.gicv5_vm.vpe_db_base = 0;
> > + vm->domain = NULL;
> > + vm->fwnode = NULL;
> > +
> > + return ret;
> > +}
> > +
> > +static void vgic_v5_teardown_per_vm_domain(struct vgic_v5_vm *vm)
> > +{
> > + if (!vm->domain)
> > + return;
> > +
> > + irq_domain_remove(vm->domain);
> > + irq_domain_free_fwnode(vm->fwnode);
> > + vm->domain = NULL;
> > + vm->fwnode = NULL;
> > +}
> > +
> > void vgic_v5_reset(struct kvm_vcpu *vcpu)
> > {
> > /*
> > @@ -167,10 +296,16 @@ void vgic_v5_reset(struct kvm_vcpu *vcpu)
> > vcpu->arch.vgic_cpu.num_pri_bits = 5;
> > }
> >
> > +void vgic_v5_teardown(struct kvm *kvm)
> > +{
> > + vgic_v5_teardown_per_vm_domain(&kvm->arch.vgic.gicv5_vm);
> > +}
>
> Since this is a global symbol, I'd like to make sure this is never
> called concurrently with anything related. Could you please add
>
> lockdep_assert_held(&kvm->arch.config_lock);
>
> here?
Done.
>
> > +
> > int vgic_v5_init(struct kvm *kvm)
> > {
> > struct kvm_vcpu *vcpu;
> > unsigned long idx;
> > + int ret;
>
> and here?
And done.
>
> >
> > if (vgic_initialized(kvm))
> > return 0;
> > @@ -182,6 +317,10 @@ int vgic_v5_init(struct kvm *kvm)
> > }
> > }
> >
> > + ret = vgic_v5_create_per_vm_domain(kvm);
> > + if (ret)
> > + return ret;
> > +
> > /* We only allow userspace to drive the SW_PPI, if it is
> > implemented. */
> > bitmap_zero(kvm->arch.vgic.gicv5_vm.userspace_ppis,
> > VGIC_V5_NR_PRIVATE_IRQS);
> > diff --git a/arch/arm64/kvm/vgic/vgic.h
> > b/arch/arm64/kvm/vgic/vgic.h
> > index f45f7e3ec4d6e..f2f5fdc3211d7 100644
> > --- a/arch/arm64/kvm/vgic/vgic.h
> > +++ b/arch/arm64/kvm/vgic/vgic.h
> > @@ -366,6 +366,7 @@ void vgic_debug_destroy(struct kvm *kvm);
> > int vgic_v5_probe(const struct gic_kvm_info *info);
> > void vgic_v5_reset(struct kvm_vcpu *vcpu);
> > int vgic_v5_init(struct kvm *kvm);
> > +void vgic_v5_teardown(struct kvm *kvm);
> > int vgic_v5_map_resources(struct kvm *kvm);
> > void vgic_v5_set_ppi_ops(struct kvm_vcpu *vcpu, u32 vintid);
> > bool vgic_v5_has_pending_ppi(struct kvm_vcpu *vcpu);
> > diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> > index 8d65a18fefb80..bff2b7c896d55 100644
> > --- a/include/kvm/arm_vgic.h
> > +++ b/include/kvm/arm_vgic.h
> > @@ -392,6 +392,10 @@ struct vgic_v5_vm {
> > * convenient way to do that).
> > */
> > DECLARE_BITMAP(vgic_ppi_hmr, VGIC_V5_NR_PRIVATE_IRQS);
> > +
> > + struct fwnode_handle *fwnode;
> > + struct irq_domain *domain;
> > + int vpe_db_base;
> > };
> >
> > struct vgic_dist {
> > diff --git a/include/linux/irqchip/arm-gic-v5.h
> > b/include/linux/irqchip/arm-gic-v5.h
> > index 83cfcd056b250..21c8a69f99bb6 100644
> > --- a/include/linux/irqchip/arm-gic-v5.h
> > +++ b/include/linux/irqchip/arm-gic-v5.h
> > @@ -613,6 +613,8 @@ void gicv5_irs_syncr(void);
> >
> > /* Embedded in kvm.arch */
> > struct gicv5_vpe {
> > + int db;
> > + bool db_fired;
> > bool resident;
> > };
>
> Thanks,
>
> M.
>
More information about the linux-arm-kernel
mailing list