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vfio/pci: enable MSI-X in interrupt restoring on dynamic allocation

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During migration restoring, vfio_enable_vectors() is called to restore
enabling MSI-X interrupts for assigned devices. It sets the range from
0 to nr_vectors to kernel to enable MSI-X and the vectors unmasked in
guest. During the MSI-X enabling, all the vectors within the range are
allocated according to the VFIO_DEVICE_SET_IRQS ioctl.

When dynamic MSI-X allocation is supported, we only want the guest
unmasked vectors being allocated and enabled. Use vector 0 with an
invalid fd to get MSI-X enabled, after that, all the vectors can be
allocated in need.

Signed-off-by: Jing Liu <jing2.liu@intel.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
This commit is contained in:
Jing Liu 2023-09-25 22:14:07 -04:00 committed by Cédric Le Goater
parent 5ebffa4e87
commit eaadba6f9b
1 changed files with 17 additions and 0 deletions
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17
hw/vfio/pci.c
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@ -402,6 +402,23 @@ static int vfio_enable_vectors(VFIOPCIDevice *vdev, bool msix)
int ret = 0, i, argsz;
int32_t *fds;
/*
* If dynamic MSI-X allocation is supported, the vectors to be allocated
* and enabled can be scattered. Before kernel enabling MSI-X, setting
* nr_vectors causes all these vectors to be allocated on host.
*
* To keep allocation as needed, use vector 0 with an invalid fd to get
* MSI-X enabled first, then set vectors with a potentially sparse set of
* eventfds to enable interrupts only when enabled in guest.
*/
if (msix && !vdev->msix->noresize) {
ret = vfio_enable_msix_no_vec(vdev);
if (ret) {
return ret;
}
}
argsz = sizeof(*irq_set) + (vdev->nr_vectors * sizeof(*fds));
irq_set = g_malloc0(argsz);