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vfio: Fix MSI-X vector expansion

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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: Alex Williamson <alex.williamson@redhat.com>
Cc: qemu-stable@nongnu.org # QEMU 2.1
This commit is contained in:
Alex Williamson 2014-08-05 13:05:52 -06:00
parent 69f87f7130
commit c048be5cc9
1 changed files with 29 additions and 9 deletions
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38
hw/misc/vfio.c
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@ -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;
@ -681,13 +690,24 @@ 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);
} else {
fds[i] = event_notifier_get_fd(&vdev->msi_vectors[i].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 {
fd = event_notifier_get_fd(&vdev->msi_vectors[i].kvm_interrupt);
}
}
fds[i] = fd;
}
ret = ioctl(vdev->fd, VFIO_DEVICE_SET_IRQS, irq_set);