Commit c048be5c authored by Alex Williamson's avatar Alex Williamson
Browse files

vfio: Fix MSI-X vector expansion 



When new MSI-X vectors are enabled we need to disable MSI-X and
re-enable it with the correct number of vectors.  That means we need
to reprogram the eventfd triggers for each vector.  Prior to f4d45d47
vector->use tracked whether a vector was masked or unmasked and we
could always pick the KVM path when available for unmasked vectors.
Now vfio doesn't track mask state itself and vector->use and virq
remains configured even for masked vectors.  Therefore we need to ask
the MSI-X code whether a vector is masked in order to select the
correct signaling path.  As noted in the comment, MSI relies on
hardware to handle masking.

Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
Cc: qemu-stable@nongnu.org # QEMU 2.1
parent 69f87f71

hw/misc/vfio.c

+29 −9
Original line number Diff line number Diff line
@@ -120,11 +120,20 @@ typedef struct VFIOINTx { 
} VFIOINTx;



typedef struct VFIOMSIVector {

    EventNotifier interrupt; /* eventfd triggered on interrupt */

    EventNotifier kvm_interrupt; /* eventfd triggered for KVM irqfd bypass */

    /*

     * Two interrupt paths are configured per vector.  The first, is only used

     * for interrupts injected via QEMU.  This is typically the non-accel path,

     * but may also be used when we want QEMU to handle masking and pending

     * bits.  The KVM path bypasses QEMU and is therefore higher performance,

     * but requires masking at the device.  virq is used to track the MSI route

     * through KVM, thus kvm_interrupt is only available when virq is set to a

     * valid (>= 0) value.

     */

    EventNotifier interrupt;

    EventNotifier kvm_interrupt;

    struct VFIODevice *vdev; /* back pointer to device */

    MSIMessage msg; /* cache the MSI message so we know when it changes */

    int virq; /* KVM irqchip route for QEMU bypass */

    int virq;

    bool use;

} VFIOMSIVector;
@@ -681,15 +690,26 @@ static int vfio_enable_vectors(VFIODevice *vdev, bool msix) 
    fds = (int32_t *)&irq_set->data;



    for (i = 0; i < vdev->nr_vectors; i++) {

        if (!vdev->msi_vectors[i].use) {

            fds[i] = -1;

        } else if (vdev->msi_vectors[i].virq >= 0) {

            fds[i] = event_notifier_get_fd(&vdev->msi_vectors[i].kvm_interrupt);

        int fd = -1;



        /*

         * MSI vs MSI-X - The guest has direct access to MSI mask and pending

         * bits, therefore we always use the KVM signaling path when setup.

         * MSI-X mask and pending bits are emulated, so we want to use the

         * KVM signaling path only when configured and unmasked.

         */

        if (vdev->msi_vectors[i].use) {

            if (vdev->msi_vectors[i].virq < 0 ||

                (msix && msix_is_masked(&vdev->pdev, i))) {

                fd = event_notifier_get_fd(&vdev->msi_vectors[i].interrupt);

            } else {

            fds[i] = event_notifier_get_fd(&vdev->msi_vectors[i].interrupt);

                fd = event_notifier_get_fd(&vdev->msi_vectors[i].kvm_interrupt);

            }

        }



        fds[i] = fd;

    }



    ret = ioctl(vdev->fd, VFIO_DEVICE_SET_IRQS, irq_set);



    g_free(irq_set);