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

["Cédric Le Goater" <clg@redhat.com>]

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 :

[   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')