On Fri, Oct 5, 2012 at 5:11 PM, Alex Williamson
<alex.williamson@xxxxxxxxxx> wrote:
> On Fri, 2012-10-05 at 16:54 +0000, Blue Swirl wrote:
>> On Wed, Sep 26, 2012 at 5:19 PM, Alex Williamson
>> <alex.williamson@xxxxxxxxxx> wrote:
>> > +
>> > +typedef struct QEMU_PACKED VFIOIRQSetFD {
>> > + struct vfio_irq_set irq_set;
>> > + int32_t fd;
>> > +} VFIOIRQSetFD;
>>
>> I'm now getting this error from Clang:
>>
>> /src/qemu/hw/vfio_pci.c:126:25: error: field 'irq_set' with variable
>> sized type 'struct vfio_irq_set' not at the end of a struct or class
>> is a GNU extension [-Werror,-Wgnu]
>> struct vfio_irq_set irq_set;
>>
>> Does the kernel really use the fd field, isn't it implicit from the
>> ioctl fd or are they different?
>
> The kernel side is defined as:
>
> struct vfio_irq_set {
> __u32 argsz;
> __u32 flags;
> __u32 index;
> __u32 start;
> __u32 count;
> __u8 data[];
> };
Then the kernel only expects vfio_irq_set structure, not VFIOIRQSetFD,
so you should use &irq_set_fd.irq_set instead of &irq_set_fd for the
ioctl(). Then VFIOIRQSetFD can be rearranged to have fd field first,
also QEMU_PACKED is not necessary.
>
> Where data is the start of a variable sized array. The data type of the
> array depends on the flags. The purpose of VFIOIRQSetFD is simply to
> make a data type that I don't need to dynamically allocate. You can
> find other cases for MSI and MSIX where we don't know the array size and
> do malloc the whole structure. For this interrupt type we know there's
> only one entry. If there's a better way to do this, let me know. VFIO
> is only available on Linux hosts, so I have no particular reason to
> avoid GNU extensions.
>
>> > +
>> > +static int vfio_enable_intx(VFIODevice *vdev)
>> > +{
>> > + VFIOIRQSetFD irq_set_fd = {
>> > + .irq_set = {
>> > + .argsz = sizeof(irq_set_fd),
>> > + .flags = VFIO_IRQ_SET_DATA_EVENTFD | VFIO_IRQ_SET_ACTION_TRIGGER,
>> > + .index = VFIO_PCI_INTX_IRQ_INDEX,
>> > + .start = 0,
>> > + .count = 1,
>> > + },
>>
>> Here the field is not even initialized.
>
> It's initialized later...
>
>> > + };
>> > + uint8_t pin = vfio_pci_read_config(&vdev->pdev, PCI_INTERRUPT_PIN, 1);
>> > + int ret;
>> > +
>> > + if (vdev->intx.disabled || !pin) {
>> > + return 0;
>> > + }
>> > +
>> > + vfio_disable_interrupts(vdev);
>> > +
>> > + vdev->intx.pin = pin - 1; /* Pin A (1) -> irq[0] */
>> > + ret = event_notifier_init(&vdev->intx.interrupt, 0);
>> > + if (ret) {
>> > + error_report("vfio: Error: event_notifier_init failed\n");
>> > + return ret;
>> > + }
>> > +
>> > + irq_set_fd.fd = event_notifier_get_fd(&vdev->intx.interrupt);
>
> Here.
>
> Thanks,
> Alex
>
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