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authorAlex Williamson <alex.williamson@redhat.com>2014-08-05 13:05:52 -0600
committerAlex Williamson <alex.williamson@redhat.com>2014-08-05 13:05:52 -0600
commitc048be5cc92ae201c339d46984476c4629275ed6 (patch)
tree36038db6fb1159301daccc8dcd1ecec080849054
parent69f87f713069f1f70f86cb65883f7d43e3aa21de (diff)
downloadqemu-arm-c048be5cc92ae201c339d46984476c4629275ed6.tar.gz
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: Alex Williamson <alex.williamson@redhat.com> Cc: qemu-stable@nongnu.org # QEMU 2.1
-rw-r--r--hw/misc/vfio.c38
1 files changed, 29 insertions, 9 deletions
diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
index 0b9eba0c84..e88b610721 100644
--- a/hw/misc/vfio.c
+++ b/hw/misc/vfio.c
@@ -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);