On Thu, Jan 29, 2026 at 09:24:53PM +0000, David Matlack wrote: > From: Vipin Sharma <[email protected]> > > Enable userspace to retrieve preserved VFIO device files from VFIO after > a Live Update by implementing the retrieve() and finish() file handler > callbacks. > > Use an anonymous inode when creating the file, since the retrieved > device file is not opened through any particular cdev inode, and the > cdev inode does not matter in practice. > > For now the retrieved file is functionally equivalent a opening the > corresponding VFIO cdev file. Subsequent commits will leverage the > preserved state associated with the retrieved file to preserve bits of > the device across Live Update. > > Signed-off-by: Vipin Sharma <[email protected]> > Co-developed-by: David Matlack <[email protected]> > Signed-off-by: David Matlack <[email protected]> > --- > drivers/vfio/device_cdev.c | 21 ++++++--- > drivers/vfio/pci/vfio_pci_liveupdate.c | 60 +++++++++++++++++++++++++- > drivers/vfio/vfio_main.c | 13 ++++++ > include/linux/vfio.h | 12 ++++++ > 4 files changed, 98 insertions(+), 8 deletions(-) >
The use of anon_inode_getfile_fmode() is clever! The abstraction is clean as well. Reviewed-by: Pranjal Shrivastava <[email protected]> Thanks! Praan > diff --git a/drivers/vfio/device_cdev.c b/drivers/vfio/device_cdev.c > index 8ceca24ac136..935f84a35875 100644 > --- a/drivers/vfio/device_cdev.c > +++ b/drivers/vfio/device_cdev.c > @@ -16,14 +16,8 @@ void vfio_init_device_cdev(struct vfio_device *device) > device->cdev.owner = THIS_MODULE; > } > > -/* > - * device access via the fd opened by this function is blocked until > - * .open_device() is called successfully during BIND_IOMMUFD. > - */ > -int vfio_device_fops_cdev_open(struct inode *inode, struct file *filep) > +int __vfio_device_fops_cdev_open(struct vfio_device *device, struct file > *filep) > { > - struct vfio_device *device = container_of(inode->i_cdev, > - struct vfio_device, cdev); > struct vfio_device_file *df; > int ret; > > @@ -52,6 +46,19 @@ int vfio_device_fops_cdev_open(struct inode *inode, struct > file *filep) > vfio_device_put_registration(device); > return ret; > } > +EXPORT_SYMBOL_GPL(__vfio_device_fops_cdev_open); > + > +/* > + * device access via the fd opened by this function is blocked until > + * .open_device() is called successfully during BIND_IOMMUFD. > + */ > +int vfio_device_fops_cdev_open(struct inode *inode, struct file *filep) > +{ > + struct vfio_device *device = container_of(inode->i_cdev, > + struct vfio_device, cdev); > + > + return __vfio_device_fops_cdev_open(device, filep); > +} > > static void vfio_df_get_kvm_safe(struct vfio_device_file *df) > { > diff --git a/drivers/vfio/pci/vfio_pci_liveupdate.c > b/drivers/vfio/pci/vfio_pci_liveupdate.c > index f01de98f1b75..7f4117181fd0 100644 > --- a/drivers/vfio/pci/vfio_pci_liveupdate.c > +++ b/drivers/vfio/pci/vfio_pci_liveupdate.c > @@ -8,6 +8,8 @@ > > #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt > > +#include <linux/anon_inodes.h> > +#include <linux/file.h> > #include <linux/kexec_handover.h> > #include <linux/kho/abi/vfio_pci.h> > #include <linux/liveupdate.h> > @@ -108,13 +110,68 @@ static int vfio_pci_liveupdate_freeze(struct > liveupdate_file_op_args *args) > return ret; > } > > +static int match_device(struct device *dev, const void *arg) > +{ > + struct vfio_device *device = container_of(dev, struct vfio_device, > device); > + const struct vfio_pci_core_device_ser *ser = arg; > + struct pci_dev *pdev; > + > + pdev = dev_is_pci(device->dev) ? to_pci_dev(device->dev) : NULL; > + if (!pdev) > + return false; > + > + return ser->bdf == pci_dev_id(pdev) && ser->domain == > pci_domain_nr(pdev->bus); > +} > + > static int vfio_pci_liveupdate_retrieve(struct liveupdate_file_op_args *args) > { > - return -EOPNOTSUPP; > + struct vfio_pci_core_device_ser *ser; > + struct vfio_device *device; > + struct file *file; > + int ret; > + > + ser = phys_to_virt(args->serialized_data); > + > + device = vfio_find_device(ser, match_device); > + if (!device) > + return -ENODEV; > + > + /* > + * Simulate opening the character device using an anonymous inode. The > + * returned file has the same properties as a cdev file (e.g. operations > + * are blocked until BIND_IOMMUFD is called). > + */ > + file = anon_inode_getfile_fmode("[vfio-device-liveupdate]", > + &vfio_device_fops, NULL, > + O_RDWR, FMODE_PREAD | FMODE_PWRITE); > + if (IS_ERR(file)) { > + ret = PTR_ERR(file); > + goto out; > + } > + > + ret = __vfio_device_fops_cdev_open(device, file); > + if (ret) { > + fput(file); > + goto out; > + } > + > + args->file = file; > + > +out: > + /* Drop the reference from vfio_find_device() */ > + put_device(&device->device); > + > + return ret; > +} > + > +static bool vfio_pci_liveupdate_can_finish(struct liveupdate_file_op_args > *args) > +{ > + return args->retrieved; > } > > static void vfio_pci_liveupdate_finish(struct liveupdate_file_op_args *args) > { > + kho_restore_free(phys_to_virt(args->serialized_data)); > } > > static const struct liveupdate_file_ops vfio_pci_liveupdate_file_ops = { > @@ -123,6 +180,7 @@ static const struct liveupdate_file_ops > vfio_pci_liveupdate_file_ops = { > .unpreserve = vfio_pci_liveupdate_unpreserve, > .freeze = vfio_pci_liveupdate_freeze, > .retrieve = vfio_pci_liveupdate_retrieve, > + .can_finish = vfio_pci_liveupdate_can_finish, > .finish = vfio_pci_liveupdate_finish, > .owner = THIS_MODULE, > }; > diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c > index 276f615f0c28..89c5feef75d5 100644 > --- a/drivers/vfio/vfio_main.c > +++ b/drivers/vfio/vfio_main.c > @@ -13,6 +13,7 @@ > #include <linux/cdev.h> > #include <linux/compat.h> > #include <linux/device.h> > +#include <linux/device/class.h> > #include <linux/fs.h> > #include <linux/idr.h> > #include <linux/iommu.h> > @@ -1758,6 +1759,18 @@ int vfio_dma_rw(struct vfio_device *device, dma_addr_t > iova, void *data, > } > EXPORT_SYMBOL(vfio_dma_rw); > > +struct vfio_device *vfio_find_device(const void *data, device_match_t match) > +{ > + struct device *device; > + > + device = class_find_device(vfio.device_class, NULL, data, match); > + if (!device) > + return NULL; > + > + return container_of(device, struct vfio_device, device); > +} > +EXPORT_SYMBOL_GPL(vfio_find_device); > + > /* > * Module/class support > */ > diff --git a/include/linux/vfio.h b/include/linux/vfio.h > index 9aa1587fea19..dc592dc00f89 100644 > --- a/include/linux/vfio.h > +++ b/include/linux/vfio.h > @@ -419,4 +419,16 @@ int vfio_virqfd_enable(void *opaque, int (*handler)(void > *, void *), > void vfio_virqfd_disable(struct virqfd **pvirqfd); > void vfio_virqfd_flush_thread(struct virqfd **pvirqfd); > > +#if IS_ENABLED(CONFIG_VFIO_DEVICE_CDEV) > +int __vfio_device_fops_cdev_open(struct vfio_device *device, struct file > *filep); > +#else > +static inline int __vfio_device_fops_cdev_open(struct vfio_device *device, > + struct file *filep) > +{ > + return -EOPNOTSUPP; > +} > +#endif /* IS_ENABLED(CONFIG_VFIO_DEVICE_CDEV) */ > + > +struct vfio_device *vfio_find_device(const void *data, device_match_t match); > + > #endif /* VFIO_H */ > -- > 2.53.0.rc1.225.gd81095ad13-goog >
