Re: [RFC PATCH v3 4/5] util/vfio-helpers: Introduce qemu_vfio_pci_init_msix_irqs()

[Alex Williamson <alex.williamson@redhat.com>]

On Tue, 18 Aug 2020 18:45:08 +0200
Philippe Mathieu-Daudé <philmd@redhat.com> wrote:

> qemu_vfio_pci_init_irq() allows us to initialize any type of IRQ,
> but only one. Introduce qemu_vfio_pci_init_msix_irqs() which is
> specific to MSIX IRQ type, and allow us to use multiple IRQs
> (thus passing multiple eventfd notifiers).
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  include/qemu/vfio-helpers.h |  2 ++
>  util/vfio-helpers.c         | 53 +++++++++++++++++++++++++++++++++++++
>  2 files changed, 55 insertions(+)
> 
> diff --git a/include/qemu/vfio-helpers.h b/include/qemu/vfio-helpers.h
> index 1f057c2b9e4..63108ebc8da 100644
> --- a/include/qemu/vfio-helpers.h
> +++ b/include/qemu/vfio-helpers.h
> @@ -28,5 +28,7 @@ void qemu_vfio_pci_unmap_bar(QEMUVFIOState *s, int index, void *bar,
>                               uint64_t offset, uint64_t size);
>  int qemu_vfio_pci_init_irq(QEMUVFIOState *s, EventNotifier *e,
>                             int irq_type, Error **errp);
> +int qemu_vfio_pci_init_msix_irqs(QEMUVFIOState *s, EventNotifier *e,
> +                                 unsigned irq_count, Error **errp);
>  
>  #endif
> diff --git a/util/vfio-helpers.c b/util/vfio-helpers.c
> index 696f2d51712..fb3a79a5bcb 100644
> --- a/util/vfio-helpers.c
> +++ b/util/vfio-helpers.c
> @@ -215,6 +215,59 @@ int qemu_vfio_pci_init_irq(QEMUVFIOState *s, EventNotifier *e,
>      return 0;
>  }
>  
> +/**
> + * Initialize device MSIX IRQs and register event notifiers.
> + * @irq_count: number of MSIX IRQs to initialize
> + * @e: Array of @irq_count notifiers (each corresponding to a MSIX IRQ)
> + */
> +int qemu_vfio_pci_init_msix_irqs(QEMUVFIOState *s, EventNotifier *e,
> +                                 unsigned irq_count, Error **errp)
> +{
> +    int r;
> +    struct vfio_irq_set *irq_set;
> +    size_t irq_set_size;
> +    struct vfio_irq_info irq_info = { .argsz = sizeof(irq_info) };
> +
> +    irq_info.index = VFIO_PCI_MSIX_IRQ_INDEX;

Nit, this could be initialized in the declaration with argsz.

> +    if (ioctl(s->device, VFIO_DEVICE_GET_IRQ_INFO, &irq_info)) {
> +        error_setg_errno(errp, errno, "Failed to get device interrupt info");
> +        return -errno;
> +    }
> +    if (irq_info.count <= irq_count) {


Shouldn't this only test strictly less than?  The API seems to leave
the problem of determining how many vectors might be available as an
exercise for the caller.  Thanks,

Alex


> +        error_setg(errp,
> +                   "Not enough device interrupts available (only %" PRIu32 ")",
> +                   irq_info.count);
> +        return -EINVAL;
> +    }
> +    if (!(irq_info.flags & VFIO_IRQ_INFO_EVENTFD)) {
> +        error_setg(errp, "Device interrupt doesn't support eventfd");
> +        return -EINVAL;
> +    }
> +
> +    irq_set_size = sizeof(*irq_set) + irq_count * sizeof(int32_t);
> +    irq_set = g_malloc0(irq_set_size);
> +
> +    /* Get to a known IRQ state */
> +    *irq_set = (struct vfio_irq_set) {
> +        .argsz = irq_set_size,
> +        .flags = VFIO_IRQ_SET_DATA_EVENTFD | VFIO_IRQ_SET_ACTION_TRIGGER,
> +        .index = irq_info.index,
> +        .start = 0,
> +        .count = irq_count,
> +    };
> +
> +    for (unsigned i = 0; i < irq_count; i++) {
> +        ((int32_t *)&irq_set->data)[i] = event_notifier_get_fd(&e[i]);
> +    }
> +    r = ioctl(s->device, VFIO_DEVICE_SET_IRQS, irq_set);
> +    g_free(irq_set);
> +    if (r) {
> +        error_setg_errno(errp, errno, "Failed to setup device interrupts");
> +        return -errno;
> +    }
> +    return 0;
> +}
> +
>  static int qemu_vfio_pci_read_config(QEMUVFIOState *s, void *buf,
>                                       int size, int ofs)
>  {