On 03/05/2019 18:15, Andre Przywara wrote:
> struct vfio_irq_set from the kernel headers contains a variable sized
> array to hold a payload. The vfio_irq_eventfd struct puts the "fd"
> member right after this, hoping it to automatically fit in the payload slot.
> But having a variable sized type not at the end of a struct is a GNU C
> extension, so clang will refuse to compile this.
>
> Solve this by somewhat doing the compiler's job and place the payload
> manually at the end of the structure.
>
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
It's odd that clang still warns about it even when passing -std=gnuXX.
The resulting code doesn't look particularly nice, but it would be good
to have the other patches upstream and this one is harmless, so:
Reviewed-by: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>
> ---
> vfio/pci.c | 21 +++++++++++++--------
> 1 file changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/vfio/pci.c b/vfio/pci.c
> index a4086326..76e24c15 100644
> --- a/vfio/pci.c
> +++ b/vfio/pci.c
> @@ -9,11 +9,16 @@
> #include <sys/time.h>
>
> /* Wrapper around UAPI vfio_irq_set */
> -struct vfio_irq_eventfd {
> +union vfio_irq_eventfd {
> struct vfio_irq_set irq;
> - int fd;
> + u8 buffer[sizeof(struct vfio_irq_set) + sizeof(int)];
> };
>
> +static void set_vfio_irq_eventd_payload(union vfio_irq_eventfd *evfd, int fd)
> +{
> + memcpy(&evfd->irq.data, &fd, sizeof(fd));
> +}
> +
> #define msi_is_enabled(state) ((state) & VFIO_PCI_MSI_STATE_ENABLED)
> #define msi_is_masked(state) ((state) & VFIO_PCI_MSI_STATE_MASKED)
> #define msi_is_empty(state) ((state) & VFIO_PCI_MSI_STATE_EMPTY)
> @@ -38,7 +43,7 @@ static int vfio_pci_enable_msis(struct kvm *kvm, struct vfio_device *vdev,
> int *eventfds;
> struct vfio_pci_device *pdev = &vdev->pci;
> struct vfio_pci_msi_common *msis = msix ? &pdev->msix : &pdev->msi;
> - struct vfio_irq_eventfd single = {
> + union vfio_irq_eventfd single = {
> .irq = {
> .argsz = sizeof(single),
> .flags = VFIO_IRQ_SET_DATA_EVENTFD |
> @@ -117,7 +122,7 @@ static int vfio_pci_enable_msis(struct kvm *kvm, struct vfio_device *vdev,
> continue;
>
> single.irq.start = i;
> - single.fd = fd;
> + set_vfio_irq_eventd_payload(&single, fd);
>
> ret = ioctl(vdev->fd, VFIO_DEVICE_SET_IRQS, &single);
> if (ret < 0) {
> @@ -1021,8 +1026,8 @@ static int vfio_pci_enable_intx(struct kvm *kvm, struct vfio_device *vdev)
> {
> int ret;
> int trigger_fd, unmask_fd;
> - struct vfio_irq_eventfd trigger;
> - struct vfio_irq_eventfd unmask;
> + union vfio_irq_eventfd trigger;
> + union vfio_irq_eventfd unmask;
> struct vfio_pci_device *pdev = &vdev->pci;
> int gsi = pdev->intx_gsi;
>
> @@ -1058,7 +1063,7 @@ static int vfio_pci_enable_intx(struct kvm *kvm, struct vfio_device *vdev)
> .start = 0,
> .count = 1,
> };
> - trigger.fd = trigger_fd;
> + set_vfio_irq_eventd_payload(&trigger, trigger_fd);
>
> ret = ioctl(vdev->fd, VFIO_DEVICE_SET_IRQS, &trigger);
> if (ret < 0) {
> @@ -1073,7 +1078,7 @@ static int vfio_pci_enable_intx(struct kvm *kvm, struct vfio_device *vdev)
> .start = 0,
> .count = 1,
> };
> - unmask.fd = unmask_fd;
> + set_vfio_irq_eventd_payload(&unmask, unmask_fd);
>
> ret = ioctl(vdev->fd, VFIO_DEVICE_SET_IRQS, &unmask);
> if (ret < 0) {
>
