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vfio-pci: preserve MSI

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Save the MSI message area as part of vfio-pci vmstate, and preserve the
interrupt and notifier eventfd's.  migrate_incoming loads the MSI data,
then the vfio-pci post_load handler finds the eventfds in CPR state,
rebuilds vector data structures, and attaches the interrupts to the new
KVM instance.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/1751493538-202042-2-git-send-email-steven.sistare@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
This commit is contained in:
Steve Sistare 2025-07-02 14:58:38 -07:00 • committed by Cédric Le Goater
parent 3f2a36d0ef
commit 30edcb4d4e
4 changed files with 157 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

52
hw/vfio/pci.c
View file

@ -29,6 +29,7 @@
#include "hw/pci/pci_bridge.h"
#include "hw/qdev-properties.h"
#include "hw/qdev-properties-system.h"
#include "hw/vfio/vfio-cpr.h"
#include "migration/vmstate.h"
#include "migration/cpr.h"
#include "qobject/qdict.h"
@ -57,20 +58,33 @@ static void vfio_disable_interrupts(VFIOPCIDevice *vdev);
static void vfio_mmap_set_enabled(VFIOPCIDevice *vdev, bool enabled);
static void vfio_msi_disable_common(VFIOPCIDevice *vdev);
/* Create new or reuse existing eventfd */
static bool vfio_notifier_init(VFIOPCIDevice *vdev, EventNotifier *e,
const char *name, int nr, Error **errp)
{
int ret = event_notifier_init(e, 0);
int fd, ret;
fd = vfio_cpr_load_vector_fd(vdev, name, nr);
if (fd >= 0) {
event_notifier_init_fd(e, fd);
return true;
}
ret = event_notifier_init(e, 0);
if (ret) {
error_setg_errno(errp, -ret, "vfio_notifier_init %s failed", name);
return false;
}
return !ret;
fd = event_notifier_get_fd(e);
vfio_cpr_save_vector_fd(vdev, name, nr, fd);
return true;
}
static void vfio_notifier_cleanup(VFIOPCIDevice *vdev, EventNotifier *e,
const char *name, int nr)
{
vfio_cpr_delete_vector_fd(vdev, name, nr);
event_notifier_cleanup(e);
}
@ -394,6 +408,14 @@ static void vfio_msi_interrupt(void *opaque)
notify(&vdev->pdev, nr);
}
void vfio_pci_msi_set_handler(VFIOPCIDevice *vdev, int nr)
{
VFIOMSIVector *vector = &vdev->msi_vectors[nr];
int fd = event_notifier_get_fd(&vector->interrupt);
qemu_set_fd_handler(fd, vfio_msi_interrupt, NULL, vector);
}
/*
* Get MSI-X enabled, but no vector enabled, by setting vector 0 with an invalid
* fd to kernel.
@ -656,6 +678,15 @@ static int vfio_msix_vector_do_use(PCIDevice *pdev, unsigned int nr,
static int vfio_msix_vector_use(PCIDevice *pdev,
unsigned int nr, MSIMessage msg)
{
/*
* Ignore the callback from msix_set_vector_notifiers during resume.
* The necessary subset of these actions is called from
* vfio_cpr_claim_vectors during post load.
*/
if (cpr_is_incoming()) {
return 0;
}
return vfio_msix_vector_do_use(pdev, nr, &msg, vfio_msi_interrupt);
}
@ -686,6 +717,12 @@ static void vfio_msix_vector_release(PCIDevice *pdev, unsigned int nr)
}
}
void vfio_pci_msix_set_notifiers(VFIOPCIDevice *vdev)
{
msix_set_vector_notifiers(&vdev->pdev, vfio_msix_vector_use,
vfio_msix_vector_release, NULL);
}
void vfio_pci_prepare_kvm_msi_virq_batch(VFIOPCIDevice *vdev)
{
assert(!vdev->defer_kvm_irq_routing);
@ -2965,6 +3002,11 @@ void vfio_pci_register_err_notifier(VFIOPCIDevice *vdev)
fd = event_notifier_get_fd(&vdev->err_notifier);
qemu_set_fd_handler(fd, vfio_err_notifier_handler, NULL, vdev);
/* Do not alter irq_signaling during vfio_realize for cpr */
if (cpr_is_incoming()) {
return;
}
if (!vfio_device_irq_set_signaling(&vdev->vbasedev, VFIO_PCI_ERR_IRQ_INDEX, 0,
VFIO_IRQ_SET_ACTION_TRIGGER, fd, &err)) {
error_reportf_err(err, VFIO_MSG_PREFIX, vdev->vbasedev.name);
@ -3032,6 +3074,12 @@ void vfio_pci_register_req_notifier(VFIOPCIDevice *vdev)
fd = event_notifier_get_fd(&vdev->req_notifier);
qemu_set_fd_handler(fd, vfio_req_notifier_handler, NULL, vdev);
/* Do not alter irq_signaling during vfio_realize for cpr */
if (cpr_is_incoming()) {
vdev->req_enabled = true;
return;
}
if (!vfio_device_irq_set_signaling(&vdev->vbasedev, VFIO_PCI_REQ_IRQ_INDEX, 0,
VFIO_IRQ_SET_ACTION_TRIGGER, fd, &err)) {
error_reportf_err(err, VFIO_MSG_PREFIX, vdev->vbasedev.name);