The vector_use callback is used to enable vector that is unmasked in
guest. The kernel used to only support static MSI-X allocation. When
allocating a new interrupt using "static MSI-X allocation" kernels,
Qemu first disables all previously allocated vectors and then
re-allocates all including the new one. The nr_vectors of VFIOPCIDevice
indicates that all vectors from 0 to nr_vectors are allocated (and may
be enabled), which is used to to loop all the possibly used vectors
When, e.g., disabling MSI-X interrupts.
Extend the vector_use function to support dynamic MSI-X allocation when
host supports the capability. Qemu therefore can individually allocate
and enable a new interrupt without affecting others or causing interrupts
lost during runtime.
Utilize nr_vectors to calculate the upper bound of enabled vectors in
dynamic MSI-X allocation mode since looping all msix_entries_nr is not
efficient and unnecessary.
Signed-off-by: Jing Liu <jing2....@intel.com>
Tested-by: Reinette Chatre <reinette.cha...@intel.com>
---
hw/vfio/pci.c | 40 +++++++++++++++++++++++++++-------------
1 file changed, 27 insertions(+), 13 deletions(-)
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 0c4ac0873d40..8c485636445c 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -512,12 +512,20 @@ static int vfio_msix_vector_do_use(PCIDevice *pdev,
unsigned int nr,
}
/*
- * We don't want to have the host allocate all possible MSI vectors
- * for a device if they're not in use, so we shutdown and incrementally
- * increase them as needed.
+ * When dynamic allocation is not supported, we don't want to have the
+ * host allocate all possible MSI vectors for a device if they're not
+ * in use, so we shutdown and incrementally increase them as needed.
+ * And nr_vectors stands for the number of vectors being allocated.
+ *
+ * When dynamic allocation is supported, let the host only allocate
+ * and enable a vector when it is in use in guest. nr_vectors stands
+ * for the upper bound of vectors being enabled (but not all of the
+ * ranges is allocated or enabled).
*/
- if (vdev->nr_vectors < nr + 1) {
+ if ((vdev->msix->irq_info_flags & VFIO_IRQ_INFO_NORESIZE) &&
+ (vdev->nr_vectors < nr + 1)) {
vdev->nr_vectors = nr + 1;
+
if (!vdev->defer_kvm_irq_routing) {
vfio_disable_irqindex(&vdev->vbasedev, VFIO_PCI_MSIX_IRQ_INDEX);
ret = vfio_enable_vectors(vdev, true);
@@ -529,16 +537,22 @@ static int vfio_msix_vector_do_use(PCIDevice *pdev,
unsigned int nr,
Error *err = NULL;
int32_t fd;
- if (vector->virq >= 0) {
- fd = event_notifier_get_fd(&vector->kvm_interrupt);
- } else {
- fd = event_notifier_get_fd(&vector->interrupt);
- }
+ if (!vdev->defer_kvm_irq_routing) {
+ if (vector->virq >= 0) {
+ fd = event_notifier_get_fd(&vector->kvm_interrupt);
+ } else {
+ fd = event_notifier_get_fd(&vector->interrupt);
+ }
- if (vfio_set_irq_signaling(&vdev->vbasedev,
- VFIO_PCI_MSIX_IRQ_INDEX, nr,
- VFIO_IRQ_SET_ACTION_TRIGGER, fd, &err)) {
- error_reportf_err(err, VFIO_MSG_PREFIX, vdev->vbasedev.name);
+ if (vfio_set_irq_signaling(&vdev->vbasedev,
+ VFIO_PCI_MSIX_IRQ_INDEX, nr,
+ VFIO_IRQ_SET_ACTION_TRIGGER, fd, &err))
{
+ error_reportf_err(err, VFIO_MSG_PREFIX, vdev->vbasedev.name);
+ }
+ }
+ /* Increase for dynamic allocation case. */
+ if (vdev->nr_vectors < nr + 1) {
+ vdev->nr_vectors = nr + 1;
}
}
--
2.27.0
