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vfio/pci: enable vector on dynamic MSI-X allocation

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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 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.liu@intel.com>
Tested-by: Reinette Chatre <reinette.chatre@intel.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 22:14:05 -04:00 • committed by Cédric Le Goater
parent 45d85f6228
commit d9e6710d7d
1 changed files with 28 additions and 18 deletions
Download patch file Download diff file Expand all files Collapse all files

20
hw/vfio/pci.c
View file

@ -470,6 +470,7 @@ static int vfio_msix_vector_do_use(PCIDevice *pdev, unsigned int nr,
VFIOPCIDevice *vdev = VFIO_PCI(pdev); VFIOPCIDevice *vdev = VFIO_PCI(pdev);
VFIOMSIVector *vector; VFIOMSIVector *vector;
int ret; int ret;
bool resizing = !!(vdev->nr_vectors < nr + 1);
trace_vfio_msix_vector_do_use(vdev->vbasedev.name, nr); trace_vfio_msix_vector_do_use(vdev->vbasedev.name, nr);
@ -512,19 +513,27 @@ 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 * When dynamic allocation is not supported, we don't want to have the
* for a device if they're not in use, so we shutdown and incrementally * host allocate all possible MSI vectors for a device if they're not
* increase them as needed. * in use, so we shutdown and incrementally increase them as needed.
* nr_vectors represents the total number of vectors allocated.
*
* When dynamic allocation is supported, let the host only allocate
* and enable a vector when it is in use in guest. nr_vectors represents
* the upper bound of vectors being enabled (but not all of the ranges
* is allocated or enabled).
*/ */
if (vdev->nr_vectors < nr + 1) { if (resizing) {
vdev->nr_vectors = nr + 1; vdev->nr_vectors = nr + 1;
}
if (!vdev->defer_kvm_irq_routing) { if (!vdev->defer_kvm_irq_routing) {
if (vdev->msix->noresize && resizing) {
vfio_disable_irqindex(&vdev->vbasedev, VFIO_PCI_MSIX_IRQ_INDEX); vfio_disable_irqindex(&vdev->vbasedev, VFIO_PCI_MSIX_IRQ_INDEX);
ret = vfio_enable_vectors(vdev, true); ret = vfio_enable_vectors(vdev, true);
if (ret) { if (ret) {
error_report("vfio: failed to enable vectors, %d", ret); error_report("vfio: failed to enable vectors, %d", ret);
} }
}
} else { } else {
Error *err = NULL; Error *err = NULL;
int32_t fd; int32_t fd;
@ -541,6 +550,7 @@ static int vfio_msix_vector_do_use(PCIDevice *pdev, unsigned int nr,
error_reportf_err(err, VFIO_MSG_PREFIX, vdev->vbasedev.name); error_reportf_err(err, VFIO_MSG_PREFIX, vdev->vbasedev.name);
} }
} }
}
/* Disable PBA emulation when nothing more is pending. */ /* Disable PBA emulation when nothing more is pending. */
clear_bit(nr, vdev->msix->pending); clear_bit(nr, vdev->msix->pending);