Re: [PULL 10/35] hw/intc: Generalize APIC helper names from kvm_* to accel_*

[Magnus Kulke <magnuskulke@linux.microsoft.com>]

On Mon, Nov 03, 2025 at 10:43:36PM +0100, Cédric Le Goater wrote:
> Hi,
> 
> On 10/9/25 09:50, Paolo Bonzini wrote:
> > From: Magnus Kulke <magnuskulke@linux.microsoft.com>
> > 
> > Rename APIC helper functions to use an accel_* prefix instead of kvm_*
> > to support use by accelerators other than KVM. This is a preparatory
> > step for integrating MSHV support with common APIC logic.
> > 
> > Signed-off-by: Magnus Kulke <magnuskulke@linux.microsoft.com>
> > Link: https://lore.kernel.org/r/20250916164847.77883-5-magnuskulke@linux.microsoft.com
> > [Remove dead definition of mshv_msi_via_irqfd_enabled. - Paolo]
> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> > ---
> >   include/system/accel-irq.h |  37 +++++++++++++
> >   include/system/mshv.h      |  17 ++++++
> >   accel/accel-irq.c          | 106 +++++++++++++++++++++++++++++++++++++
> >   hw/intc/ioapic.c           |  20 ++++---
> >   hw/virtio/virtio-pci.c     |  21 ++++----
> >   accel/meson.build          |   2 +-
> >   6 files changed, 185 insertions(+), 18 deletions(-)
> >   create mode 100644 include/system/accel-irq.h
> >   create mode 100644 accel/accel-irq.c
> 
> This change seems to introduce a regression with interrupt remapping
> when running a VM configured with an intel-iommu device and an assigned
> PCI VF. At boot, Linux complains with :
> 

Thank you for reporting, Cédric. From glancing over it, it looks like a
typo: we check for `ACCEL_KERNEL_GSI_IRQFD_POSSIBLE` instead of
`ACCEL_GSI_IRQFD_POSSIBLE` in ioapic.c. The former doesn't seem to be
defined anywhere.

Can you verify if changing that fixes the issue for you?

s/ACCEL_KERNEL_GSI_IRQFD_POSSIBLE/ACCEL_GSI_IRQFD_POSSIBLE/g

best,

magnus

> [   15.416794] __common_interrupt: 2.37 No irq handler for vector
> [   15.417266] __common_interrupt: 2.37 No irq handler for vector
> [   15.417733] __common_interrupt: 2.37 No irq handler for vector
> [   15.418202] __common_interrupt: 2.37 No irq handler for vector
> [   15.418670] __common_interrupt: 2.37 No irq handler for vector
> [   15.419143] __common_interrupt: 2.37 No irq handler for vector
> [   15.419608] __common_interrupt: 2.37 No irq handler for vector
> [   15.420094] __common_interrupt: 2.37 No irq handler for vector
> [   15.420556] __common_interrupt: 2.37 No irq handler for vector
> 
> 
> CC’ingg Zhenzhong, Joao, Clement for awareness and their expertise
> in intel-iommu and interrupt remapping.
> 
> Thanks,
> 
> C.
> 
> 
> 
> > 
> > diff --git a/include/system/accel-irq.h b/include/system/accel-irq.h
> > new file mode 100644
> > index 00000000000..671fb7dfdbb
> > --- /dev/null
> > +++ b/include/system/accel-irq.h
> > @@ -0,0 +1,37 @@
> > +/*
> > + * Accelerated irqchip abstraction
> > + *
> > + * Copyright Microsoft, Corp. 2025
> > + *
> > + * Authors: Ziqiao Zhou <ziqiaozhou@microsoft.com>
> > + *          Magnus Kulke <magnuskulke@microsoft.com>
> > + *
> > + * SPDX-License-Identifier: GPL-2.0-or-later
> > + */
> > +
> > +#ifndef SYSTEM_ACCEL_IRQ_H
> > +#define SYSTEM_ACCEL_IRQ_H
> > +#include "hw/pci/msi.h"
> > +#include "qemu/osdep.h"
> > +#include "system/kvm.h"
> > +#include "system/mshv.h"
> > +
> > +static inline bool accel_msi_via_irqfd_enabled(void)
> > +{
> > +    return mshv_msi_via_irqfd_enabled() || kvm_msi_via_irqfd_enabled();
> > +}
> > +
> > +static inline bool accel_irqchip_is_split(void)
> > +{
> > +    return mshv_msi_via_irqfd_enabled() || kvm_irqchip_is_split();
> > +}
> > +
> > +int accel_irqchip_add_msi_route(KVMRouteChange *c, int vector, PCIDevice *dev);
> > +int accel_irqchip_update_msi_route(int vector, MSIMessage msg, PCIDevice *dev);
> > +void accel_irqchip_commit_route_changes(KVMRouteChange *c);
> > +void accel_irqchip_commit_routes(void);
> > +void accel_irqchip_release_virq(int virq);
> > +int accel_irqchip_add_irqfd_notifier_gsi(EventNotifier *n, EventNotifier *rn,
> > +                                         int virq);
> > +int accel_irqchip_remove_irqfd_notifier_gsi(EventNotifier *n, int virq);
> > +#endif
> > diff --git a/include/system/mshv.h b/include/system/mshv.h
> > index 342f1ef6a98..2a504ed81f2 100644
> > --- a/include/system/mshv.h
> > +++ b/include/system/mshv.h
> > @@ -22,4 +22,21 @@
> >   #define CONFIG_MSHV_IS_POSSIBLE
> >   #endif
> > +#ifdef CONFIG_MSHV_IS_POSSIBLE
> > +extern bool mshv_allowed;
> > +#define mshv_enabled() (mshv_allowed)
> > +#else /* CONFIG_MSHV_IS_POSSIBLE */
> > +#define mshv_enabled() false
> > +#endif
> > +#define mshv_msi_via_irqfd_enabled() false
> > +
> > +/* interrupt */
> > +int mshv_irqchip_add_msi_route(int vector, PCIDevice *dev);
> > +int mshv_irqchip_update_msi_route(int virq, MSIMessage msg, PCIDevice *dev);
> > +void mshv_irqchip_commit_routes(void);
> > +void mshv_irqchip_release_virq(int virq);
> > +int mshv_irqchip_add_irqfd_notifier_gsi(const EventNotifier *n,
> > +                                        const EventNotifier *rn, int virq);
> > +int mshv_irqchip_remove_irqfd_notifier_gsi(const EventNotifier *n, int virq);
> > +
> >   #endif
> > diff --git a/accel/accel-irq.c b/accel/accel-irq.c
> > new file mode 100644
> > index 00000000000..7f864e35c4e
> > --- /dev/null
> > +++ b/accel/accel-irq.c
> > @@ -0,0 +1,106 @@
> > +/*
> > + * Accelerated irqchip abstraction
> > + *
> > + * Copyright Microsoft, Corp. 2025
> > + *
> > + * Authors: Ziqiao Zhou <ziqiaozhou@microsoft.com>
> > + *          Magnus Kulke <magnuskulke@microsoft.com>
> > + *
> > + * SPDX-License-Identifier: GPL-2.0-or-later
> > + */
> > +
> > +#include "qemu/osdep.h"
> > +#include "hw/pci/msi.h"
> > +
> > +#include "system/kvm.h"
> > +#include "system/mshv.h"
> > +#include "system/accel-irq.h"
> > +
> > +int accel_irqchip_add_msi_route(KVMRouteChange *c, int vector, PCIDevice *dev)
> > +{
> > +#ifdef CONFIG_MSHV_IS_POSSIBLE
> > +    if (mshv_msi_via_irqfd_enabled()) {
> > +        return mshv_irqchip_add_msi_route(vector, dev);
> > +    }
> > +#endif
> > +    if (kvm_enabled()) {
> > +        return kvm_irqchip_add_msi_route(c, vector, dev);
> > +    }
> > +    return -ENOSYS;
> > +}
> > +
> > +int accel_irqchip_update_msi_route(int vector, MSIMessage msg, PCIDevice *dev)
> > +{
> > +#ifdef CONFIG_MSHV_IS_POSSIBLE
> > +    if (mshv_msi_via_irqfd_enabled()) {
> > +        return mshv_irqchip_update_msi_route(vector, msg, dev);
> > +    }
> > +#endif
> > +    if (kvm_enabled()) {
> > +        return kvm_irqchip_update_msi_route(kvm_state, vector, msg, dev);
> > +    }
> > +    return -ENOSYS;
> > +}
> > +
> > +void accel_irqchip_commit_route_changes(KVMRouteChange *c)
> > +{
> > +#ifdef CONFIG_MSHV_IS_POSSIBLE
> > +    if (mshv_msi_via_irqfd_enabled()) {
> > +        mshv_irqchip_commit_routes();
> > +    }
> > +#endif
> > +    if (kvm_enabled()) {
> > +        kvm_irqchip_commit_route_changes(c);
> > +    }
> > +}
> > +
> > +void accel_irqchip_commit_routes(void)
> > +{
> > +#ifdef CONFIG_MSHV_IS_POSSIBLE
> > +    if (mshv_msi_via_irqfd_enabled()) {
> > +        mshv_irqchip_commit_routes();
> > +    }
> > +#endif
> > +    if (kvm_enabled()) {
> > +        kvm_irqchip_commit_routes(kvm_state);
> > +    }
> > +}
> > +
> > +void accel_irqchip_release_virq(int virq)
> > +{
> > +#ifdef CONFIG_MSHV_IS_POSSIBLE
> > +    if (mshv_msi_via_irqfd_enabled()) {
> > +        mshv_irqchip_release_virq(virq);
> > +    }
> > +#endif
> > +    if (kvm_enabled()) {
> > +        kvm_irqchip_release_virq(kvm_state, virq);
> > +    }
> > +}
> > +
> > +int accel_irqchip_add_irqfd_notifier_gsi(EventNotifier *n, EventNotifier *rn,
> > +                                         int virq)
> > +{
> > +#ifdef CONFIG_MSHV_IS_POSSIBLE
> > +    if (mshv_msi_via_irqfd_enabled()) {
> > +        return mshv_irqchip_add_irqfd_notifier_gsi(n, rn, virq);
> > +    }
> > +#endif
> > +    if (kvm_enabled()) {
> > +        return kvm_irqchip_add_irqfd_notifier_gsi(kvm_state, n, rn, virq);
> > +    }
> > +    return -ENOSYS;
> > +}
> > +
> > +int accel_irqchip_remove_irqfd_notifier_gsi(EventNotifier *n, int virq)
> > +{
> > +#ifdef CONFIG_MSHV_IS_POSSIBLE
> > +    if (mshv_msi_via_irqfd_enabled()) {
> > +        return mshv_irqchip_remove_irqfd_notifier_gsi(n, virq);
> > +    }
> > +#endif
> > +    if (kvm_enabled()) {
> > +        return kvm_irqchip_remove_irqfd_notifier_gsi(kvm_state, n, virq);
> > +    }
> > +    return -ENOSYS;
> > +}
> > diff --git a/hw/intc/ioapic.c b/hw/intc/ioapic.c
> > index 133bef852d1..e431d003117 100644
> > --- a/hw/intc/ioapic.c
> > +++ b/hw/intc/ioapic.c
> > @@ -30,12 +30,18 @@
> >   #include "hw/intc/ioapic_internal.h"
> >   #include "hw/pci/msi.h"
> >   #include "hw/qdev-properties.h"
> > +#include "system/accel-irq.h"
> >   #include "system/kvm.h"
> >   #include "system/system.h"
> >   #include "hw/i386/apic-msidef.h"
> >   #include "hw/i386/x86-iommu.h"
> >   #include "trace.h"
> > +
> > +#if defined(CONFIG_KVM) || defined(CONFIG_MSHV)
> > +#define ACCEL_GSI_IRQFD_POSSIBLE
> > +#endif
> > +
> >   #define APIC_DELIVERY_MODE_SHIFT 8
> >   #define APIC_POLARITY_SHIFT 14
> >   #define APIC_TRIG_MODE_SHIFT 15
> > @@ -191,10 +197,10 @@ static void ioapic_set_irq(void *opaque, int vector, int level)
> >   static void ioapic_update_kvm_routes(IOAPICCommonState *s)
> >   {
> > -#ifdef CONFIG_KVM
> > +#ifdef ACCEL_GSI_IRQFD_POSSIBLE
> >       int i;
> > -    if (kvm_irqchip_is_split()) {
> > +    if (accel_irqchip_is_split()) {
> >           for (i = 0; i < IOAPIC_NUM_PINS; i++) {
> >               MSIMessage msg;
> >               struct ioapic_entry_info info;
> > @@ -202,15 +208,15 @@ static void ioapic_update_kvm_routes(IOAPICCommonState *s)
> >               if (!info.masked) {
> >                   msg.address = info.addr;
> >                   msg.data = info.data;
> > -                kvm_irqchip_update_msi_route(kvm_state, i, msg, NULL);
> > +                accel_irqchip_update_msi_route(i, msg, NULL);
> >               }
> >           }
> > -        kvm_irqchip_commit_routes(kvm_state);
> > +        accel_irqchip_commit_routes();
> >       }
> >   #endif
> >   }
> > -#ifdef CONFIG_KVM
> > +#ifdef ACCEL_KERNEL_GSI_IRQFD_POSSIBLE
> >   static void ioapic_iec_notifier(void *private, bool global,
> >                                   uint32_t index, uint32_t mask)
> >   {
> > @@ -428,11 +434,11 @@ static const MemoryRegionOps ioapic_io_ops = {
> >   static void ioapic_machine_done_notify(Notifier *notifier, void *data)
> >   {
> > -#ifdef CONFIG_KVM
> > +#ifdef ACCEL_KERNEL_GSI_IRQFD_POSSIBLE
> >       IOAPICCommonState *s = container_of(notifier, IOAPICCommonState,
> >                                           machine_done);
> > -    if (kvm_irqchip_is_split()) {
> > +    if (accel_irqchip_is_split()) {
> >           X86IOMMUState *iommu = x86_iommu_get_default();
> >           if (iommu) {
> >               /* Register this IOAPIC with IOMMU IEC notifier, so that
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index 767216d7959..0cdc16217ff 100644
> > --- a/hw/virtio/virtio-pci.c
> > +++ b/hw/virtio/virtio-pci.c
> > @@ -34,6 +34,7 @@
> >   #include "hw/pci/msi.h"
> >   #include "hw/pci/msix.h"
> >   #include "hw/loader.h"
> > +#include "system/accel-irq.h"
> >   #include "system/kvm.h"
> >   #include "hw/virtio/virtio-pci.h"
> >   #include "qemu/range.h"
> > @@ -825,11 +826,11 @@ static int kvm_virtio_pci_vq_vector_use(VirtIOPCIProxy *proxy,
> >       if (irqfd->users == 0) {
> >           KVMRouteChange c = kvm_irqchip_begin_route_changes(kvm_state);
> > -        ret = kvm_irqchip_add_msi_route(&c, vector, &proxy->pci_dev);
> > +        ret = accel_irqchip_add_msi_route(&c, vector, &proxy->pci_dev);
> >           if (ret < 0) {
> >               return ret;
> >           }
> > -        kvm_irqchip_commit_route_changes(&c);
> > +        accel_irqchip_commit_route_changes(&c);
> >           irqfd->virq = ret;
> >       }
> >       irqfd->users++;
> > @@ -841,7 +842,7 @@ static void kvm_virtio_pci_vq_vector_release(VirtIOPCIProxy *proxy,
> >   {
> >       VirtIOIRQFD *irqfd = &proxy->vector_irqfd[vector];
> >       if (--irqfd->users == 0) {
> > -        kvm_irqchip_release_virq(kvm_state, irqfd->virq);
> > +        accel_irqchip_release_virq(irqfd->virq);
> >       }
> >   }
> > @@ -850,7 +851,7 @@ static int kvm_virtio_pci_irqfd_use(VirtIOPCIProxy *proxy,
> >                                    unsigned int vector)
> >   {
> >       VirtIOIRQFD *irqfd = &proxy->vector_irqfd[vector];
> > -    return kvm_irqchip_add_irqfd_notifier_gsi(kvm_state, n, NULL, irqfd->virq);
> > +    return accel_irqchip_add_irqfd_notifier_gsi(n, NULL, irqfd->virq);
> >   }
> >   static void kvm_virtio_pci_irqfd_release(VirtIOPCIProxy *proxy,
> > @@ -860,7 +861,7 @@ static void kvm_virtio_pci_irqfd_release(VirtIOPCIProxy *proxy,
> >       VirtIOIRQFD *irqfd = &proxy->vector_irqfd[vector];
> >       int ret;
> > -    ret = kvm_irqchip_remove_irqfd_notifier_gsi(kvm_state, n, irqfd->virq);
> > +    ret = accel_irqchip_remove_irqfd_notifier_gsi(n, irqfd->virq);
> >       assert(ret == 0);
> >   }
> >   static int virtio_pci_get_notifier(VirtIOPCIProxy *proxy, int queue_no,
> > @@ -995,12 +996,12 @@ static int virtio_pci_one_vector_unmask(VirtIOPCIProxy *proxy,
> >       if (proxy->vector_irqfd) {
> >           irqfd = &proxy->vector_irqfd[vector];
> >           if (irqfd->msg.data != msg.data || irqfd->msg.address != msg.address) {
> > -            ret = kvm_irqchip_update_msi_route(kvm_state, irqfd->virq, msg,
> > -                                               &proxy->pci_dev);
> > +            ret = accel_irqchip_update_msi_route(irqfd->virq, msg,
> > +                                                 &proxy->pci_dev);
> >               if (ret < 0) {
> >                   return ret;
> >               }
> > -            kvm_irqchip_commit_routes(kvm_state);
> > +            accel_irqchip_commit_routes();
> >           }
> >       }
> > @@ -1229,7 +1230,7 @@ static int virtio_pci_set_guest_notifiers(DeviceState *d, int nvqs, bool assign)
> >       VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
> >       int r, n;
> >       bool with_irqfd = msix_enabled(&proxy->pci_dev) &&
> > -        kvm_msi_via_irqfd_enabled();
> > +        accel_msi_via_irqfd_enabled() ;
> >       nvqs = MIN(nvqs, VIRTIO_QUEUE_MAX);
> > @@ -1433,7 +1434,7 @@ static void virtio_pci_set_vector(VirtIODevice *vdev,
> >                                     uint16_t new_vector)
> >   {
> >       bool kvm_irqfd = (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
> > -        msix_enabled(&proxy->pci_dev) && kvm_msi_via_irqfd_enabled();
> > +        msix_enabled(&proxy->pci_dev) && accel_msi_via_irqfd_enabled();
> >       if (new_vector == old_vector) {
> >           return;
> > diff --git a/accel/meson.build b/accel/meson.build
> > index 25b0f100b51..6349efe682f 100644
> > --- a/accel/meson.build
> > +++ b/accel/meson.build
> > @@ -1,6 +1,6 @@
> >   common_ss.add(files('accel-common.c'))
> >   specific_ss.add(files('accel-target.c'))
> > -system_ss.add(files('accel-system.c', 'accel-blocker.c', 'accel-qmp.c'))
> > +system_ss.add(files('accel-system.c', 'accel-blocker.c', 'accel-qmp.c', 'accel-irq.c'))
> >   user_ss.add(files('accel-user.c'))
> >   subdir('tcg')