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vfio/iommufd: preserve descriptors

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Save the iommu and vfio device fd in CPR state when it is created.
After CPR, the fd number is found in CPR state and reused.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Link: https://lore.kernel.org/qemu-devel/1751493538-202042-16-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 14:58:52 -07:00 • committed by Cédric Le Goater
parent f2f3e4667e
commit 2a3f0a59bd
3 changed files with 40 additions and 14 deletions
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35
backends/iommufd.c
View file

@ -16,12 +16,18 @@
#include "qemu/module.h"
#include "qom/object_interfaces.h"
#include "qemu/error-report.h"
#include "migration/cpr.h"
#include "monitor/monitor.h"
#include "trace.h"
#include "hw/vfio/vfio-device.h"
#include <sys/ioctl.h>
#include <linux/iommufd.h>
static const char *iommufd_fd_name(IOMMUFDBackend *be)
{
return object_get_canonical_path_component(OBJECT(be));
}
static void iommufd_backend_init(Object *obj)
{
IOMMUFDBackend *be = IOMMUFD_BACKEND(obj);
@ -64,11 +70,27 @@ static bool iommufd_backend_can_be_deleted(UserCreatable *uc)
return !be->users;
}
static void iommufd_backend_complete(UserCreatable *uc, Error **errp)
{
IOMMUFDBackend *be = IOMMUFD_BACKEND(uc);
const char *name = iommufd_fd_name(be);
if (!be->owned) {
/* fd came from the command line. Fetch updated value from cpr state. */
if (cpr_is_incoming()) {
be->fd = cpr_find_fd(name, 0);
} else {
cpr_save_fd(name, 0, be->fd);
}
}
}
static void iommufd_backend_class_init(ObjectClass *oc, const void *data)
{
UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
ucc->can_be_deleted = iommufd_backend_can_be_deleted;
ucc->complete = iommufd_backend_complete;
object_class_property_add_str(oc, "fd", NULL, iommufd_backend_set_fd);
}
@ -102,7 +124,7 @@ bool iommufd_backend_connect(IOMMUFDBackend *be, Error **errp)
int fd;
if (be->owned && !be->users) {
fd = qemu_open("/dev/iommu", O_RDWR, errp);
fd = cpr_open_fd("/dev/iommu", O_RDWR, iommufd_fd_name(be), 0, errp);
if (fd < 0) {
return false;
}
@ -127,14 +149,15 @@ void iommufd_backend_disconnect(IOMMUFDBackend *be)
goto out;
}
be->users--;
if (!be->users && be->owned) {
close(be->fd);
be->fd = -1;
}
out:
if (!be->users) {
vfio_iommufd_cpr_unregister_iommufd(be);
if (be->owned) {
cpr_delete_fd(iommufd_fd_name(be), 0);
close(be->fd);
be->fd = -1;
}
}
out:
trace_iommufd_backend_disconnect(be->fd, be->users);
}

10
hw/vfio/cpr-iommufd.c
View file

@ -166,12 +166,18 @@ void vfio_iommufd_cpr_unregister_container(VFIOIOMMUFDContainer *container)
void vfio_iommufd_cpr_register_device(VFIODevice *vbasedev)
{
if (!cpr_is_incoming()) {
/*
* Beware fd may have already been saved by vfio_device_set_fd,
* so call resave to avoid a duplicate entry.
*/
cpr_resave_fd(vbasedev->name, 0, vbasedev->fd);
vfio_cpr_save_device(vbasedev);
}
}
void vfio_iommufd_cpr_unregister_device(VFIODevice *vbasedev)
{
cpr_delete_fd(vbasedev->name, 0);
vfio_cpr_delete_device(vbasedev->name);
}
@ -180,5 +186,9 @@ void vfio_cpr_load_device(VFIODevice *vbasedev)
if (cpr_is_incoming()) {
bool ret = vfio_cpr_find_device(vbasedev);
g_assert(ret);
if (vbasedev->fd < 0) {
vbasedev->fd = cpr_find_fd(vbasedev->name, 0);
}
}
}

9
hw/vfio/device.c
View file

@ -351,14 +351,7 @@ void vfio_device_free_name(VFIODevice *vbasedev)
void vfio_device_set_fd(VFIODevice *vbasedev, const char *str, Error **errp)
{
ERRP_GUARD();
int fd = monitor_fd_param(monitor_cur(), str, errp);
if (fd < 0) {
error_prepend(errp, "Could not parse remote object fd %s:", str);
return;
}
vbasedev->fd = fd;
vbasedev->fd = cpr_get_fd_param(vbasedev->dev->id, str, 0, errp);
}
static VFIODeviceIOOps vfio_device_io_ops_ioctl;