Re: [PATCH v2 15/16] vfio/pci: Preserve the iommufd state of the vfio cdev

[Samiullah Khawaja]

On Wed, May 20, 2026 at 12:57:40AM +0000, Pranjal Shrivastava wrote:
> On Mon, Apr 27, 2026 at 05:56:32PM +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 specific state of
> > the device and also the attach iommu HW unit.
> >
> > Once the device and its iommufd attachment is preserved, it cannot be
> > detached or attached to another IOAS until it is unpreserved.
> >
> > Signed-off-by: Samiullah Khawaja <skhawaja@xxxxxxxxxx>
> > ---
> >  drivers/vfio/device_cdev.c             | 10 ++++++++
> >  drivers/vfio/pci/vfio_pci_liveupdate.c | 33 +++++++++++++++++++++++++-
> >  2 files changed, 42 insertions(+), 1 deletion(-)
>
> [...]
>
> > diff --git a/drivers/vfio/pci/vfio_pci_liveupdate.c b/drivers/vfio/pci/vfio_pci_liveupdate.c
> > index 976ef17e6103..b56d80379ffc 100644
> > --- a/drivers/vfio/pci/vfio_pci_liveupdate.c
> > +++ b/drivers/vfio/pci/vfio_pci_liveupdate.c
> > @@ -108,10 +108,13 @@
> >  #include <linux/kho/abi/vfio_pci.h>
> >  #include <linux/liveupdate.h>
> >  #include <linux/errno.h>
> > +#include <linux/iommufd.h>
> >  #include <linux/vfio.h>
> >
> >  #include "vfio_pci_priv.h"
> >
> > +MODULE_IMPORT_NS("IOMMUFD");
> > +
> >  static bool vfio_pci_liveupdate_can_preserve(struct liveupdate_file_handler *handler,
> >  					     struct file *file)
> >  {
> > @@ -153,9 +156,26 @@ static int vfio_pci_liveupdate_preserve(struct liveupdate_file_op_args *args)
> >  	vdev = container_of(device, struct vfio_pci_core_device, vdev);
> >  	pdev = vdev->pdev;
> >
> > +#ifdef CONFIG_IOMMU_LIVEUPDATE
> > +	/* If iommufd is attached, preserve the underlying domain */
> > +	mutex_lock(&device->dev_set->lock);
> > +	if (device->iommufd_attached) {
> > +		u64 token, preserved_state;
> > +
> > +		ret = iommufd_device_preserve(args->session,
> > +					      device->iommufd_device,
> > +					      &token, &preserved_state);
> > +		if (ret) {
> > +			mutex_unlock(&device->dev_set->lock);
> > +			return ret;
> > +		}
> > +	}
> > +	mutex_unlock(&device->dev_set->lock);
> > +#endif
> > +
> >  	ret = pci_liveupdate_preserve(pdev);
> >  	if (ret)
> > -		return ret;
> > +		goto err_iommufd_unpreserve;
>
> Nit: Would we hit the WARN in patch 14 if (device->iommufd_attached) was
> false here? Should we check if (device->iommufd_attached) below before
> calling unpreserve?

Agreed. I will update this.
> >  	ser = kho_alloc_preserve(sizeof(*ser));
> >  	if (IS_ERR(ser)) {
> > @@ -170,6 +190,9 @@ static int vfio_pci_liveupdate_preserve(struct liveupdate_file_op_args *args)
> >  	args->serialized_data = virt_to_phys(ser);
> >  	return 0;
> >
> > +err_iommufd_unpreserve:
> > +	iommufd_device_unpreserve(args->session, device->iommufd_device);
> > +
> >  err_unpreserve:
> >  	pci_liveupdate_unpreserve(pdev);
> >  	return ret;
>
> With that nit:
>
> Reviewed-by: Pranjal Shrivastava <praan@xxxxxxxxxx>
>
> Thanks,
> Praan

Thanks,
Sami