Re: [PATCH 13/14] vfio/pci: Preserve the iommufd state of the vfio cdev

Samiullah Khawaja
2026-03-03T18:35:59Z

On Tue, Feb 17, 2026 at 04:18:08AM +0000, Ankit Soni wrote:
>On Tue, Feb 03, 2026 at 10:09:47PM +0000, Samiullah Khawaja wrote:
>> If the vfio cdev is attached to an iommufd, preserve the state of the
>> attached iommufd also. Basically preserve the iommu state of the device
>> and also the attached domain. The token returned by the preservation API
>> will be used to restore/rebind to the iommufd state after liveupdate.
>>
>> Signed-off-by: Samiullah Khawaja <skhawaja@google.com>
>> ---
>> drivers/vfio/pci/vfio_pci_liveupdate.c | 28 +++++++++++++++++++++++++-
>> include/linux/kho/abi/vfio_pci.h | 10 +++++++++
>> 2 files changed, 37 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/vfio/pci/vfio_pci_liveupdate.c b/drivers/vfio/pci/vfio_pci_liveupdate.c
>> index c52d6bdb455f..af6fbfb7a65c 100644
>> --- a/drivers/vfio/pci/vfio_pci_liveupdate.c
>> +++ b/drivers/vfio/pci/vfio_pci_liveupdate.c
>> @@ -15,6 +15,7 @@
>> #include <linux/liveupdate.h>
>> #include <linux/errno.h>
>> #include <linux/vfio.h>
>> +#include <linux/iommufd.h>
>>
>> #include "vfio_pci_priv.h"
>>
>> @@ -39,6 +40,7 @@ static int vfio_pci_liveupdate_preserve(struct liveupdate_file_op_args *args)
>> struct vfio_pci_core_device_ser *ser;
>> struct vfio_pci_core_device *vdev;
>> struct pci_dev *pdev;
>> + u64 token = 0;
>>
>> vdev = container_of(device, struct vfio_pci_core_device, vdev);
>> pdev = vdev->pdev;
>> @@ -49,15 +51,32 @@ static int vfio_pci_liveupdate_preserve(struct liveupdate_file_op_args *args)
>> if (vfio_pci_is_intel_display(pdev))
>> return -EINVAL;
>>
>> +#if CONFIG_IOMMU_LIVEUPDATE
>> + /* If iommufd is attached, preserve the underlying domain */
>> + if (device->iommufd_attached) {
>> + int err = iommufd_device_preserve(args->session,
>> + device->iommufd_device,
>> + &token);
>> + if (err < 0)
>> + return err;
>> + }
>> +#endif
>> +
>> ser = kho_alloc_preserve(sizeof(*ser));
>> - if (IS_ERR(ser))
>> + if (IS_ERR(ser)) {
>> + if (device->iommufd_attached)
>> + iommufd_device_unpreserve(args->session,
>> + device->iommufd_device, token);
>> +
>
>To use iommufd_device_preserve()/iommufd_device_unpreserve(),
>looks like the IOMMUFD namespace import is missing here — MODULE_IMPORT_NS("IOMMUFD");
>
>-Ankit

Agreed, I will add it to this file in v2.
>
>> return PTR_ERR(ser);
>> + }
>>
>> pci_liveupdate_outgoing_preserve(pdev);
>>
>> ser->bdf = pci_dev_id(pdev);
>> ser->domain = pci_domain_nr(pdev->bus);
>> ser->reset_works = vdev->reset_works;
>> + ser->iommufd_ser.token = token;
>>
>> args->serialized_data = virt_to_phys(ser);
>> return 0;
>> @@ -66,6 +85,13 @@ static int vfio_pci_liveupdate_preserve(struct liveupdate_file_op_args *args)
>> static void vfio_pci_liveupdate_unpreserve(struct liveupdate_file_op_args *args)
>> {
>> struct vfio_device *device = vfio_device_from_file(args->file);
>> + struct vfio_pci_core_device_ser *ser;
>> +
>> + ser = phys_to_virt(args->serialized_data);
>> + if (device->iommufd_attached)
>> + iommufd_device_unpreserve(args->session,
>> + device->iommufd_device,
>> + ser->iommufd_ser.token);
>>
>> pci_liveupdate_outgoing_unpreserve(to_pci_dev(device->dev));
>> kho_unpreserve_free(phys_to_virt(args->serialized_data));
>> diff --git a/include/linux/kho/abi/vfio_pci.h b/include/linux/kho/abi/vfio_pci.h
>> index 6c3d3c6dfc09..d01bd58711c2 100644
>> --- a/include/linux/kho/abi/vfio_pci.h
>> +++ b/include/linux/kho/abi/vfio_pci.h
>> @@ -28,6 +28,15 @@
>>
>> #define VFIO_PCI_LUO_FH_COMPATIBLE "vfio-pci-v1"
>>
>> +/**
>> + * struct vfio_iommufd_ser - Serialized state of the attached iommufd.
>> + *
>> + * @token: The token of the bound iommufd state.
>> + */
>> +struct vfio_iommufd_ser {
>> + u32 token;
>> +} __packed;
>> +
>> /**
>> * struct vfio_pci_core_device_ser - Serialized state of a single VFIO PCI
>> * device.
>> @@ -40,6 +49,7 @@ struct vfio_pci_core_device_ser {
>> u16 bdf;
>> u16 domain;
>> u8 reset_works;
>> + struct vfio_iommufd_ser iommufd_ser;
>> } __packed;
>>
>> #endif /* _LINUX_LIVEUPDATE_ABI_VFIO_PCI_H */
>> --
>> 2.53.0.rc2.204.g2597b5adb4-goog
>>

Thanks for looking at this.

Sami