Re: [PATCH v2 04/16] iommu: Implement device and IOMMU HW preservation

[Ankit Soni]

On Mon, Apr 27, 2026 at 05:56:21PM +0000, Samiullah Khawaja wrote:
> Add IOMMU ops to preserve/unpreserve a device. These can be implemented
> by the IOMMU drivers that support preservation of devices that have
> their IOMMU domains preserved. During device preservation the state of
> the associated IOMMU is also preserved as dependency.
> 
> Signed-off-by: Samiullah Khawaja <skhawaja@xxxxxxxxxx>
> ---
 
[..]

> +void iommu_unpreserve_device(struct iommu_domain *domain, struct device *dev)
> +{
> +	struct iommu_flb_obj *flb_obj;
> +	struct iommu_device_ser *iommu_device_ser;
> +	struct dev_iommu *iommu;
> +	struct pci_dev *pdev;
> +	int ret;
> +
> +	if (!dev_is_pci(dev))
> +		return;
> +
> +	if (!iommu_group_dma_owner_claimed(dev->iommu_group))
> +		return;
> +
> +	pdev = to_pci_dev(dev);

nit

pdev is declared and assigned, but never used here.

> +	iommu = dev->iommu;
> +	if (!iommu->iommu_dev->ops->unpreserve_device ||
> +	    !iommu->iommu_dev->ops->unpreserve)
> +		return;
> +
> +	ret = liveupdate_flb_get_outgoing(&iommu_flb, (void **)&flb_obj);
> +	if (WARN_ON(ret))
> +		return;
> +
> +	guard(mutex)(&flb_obj->lock);
> +	iommu_device_ser = dev_iommu_preserved_state(dev);
> +	if (WARN_ON(!iommu_device_ser))
> +		return;
> +
> +	iommu->iommu_dev->ops->unpreserve_device(dev, iommu_device_ser);
> +	dev->iommu->device_ser = NULL;
> +
> +	iommu_unpreserve_locked(iommu->iommu_dev, flb_obj);
> +}
> diff --git a/include/linux/iommu-liveupdate.h b/include/linux/iommu-liveupdate.h
> index 6019cfc27428..279c7ab04f09 100644
> --- a/include/linux/iommu-liveupdate.h
> +++ b/include/linux/iommu-liveupdate.h
> @@ -8,14 +8,37 @@
>  #ifndef _LINUX_IOMMU_LIVEUPDATE_H
>  #define _LINUX_IOMMU_LIVEUPDATE_H
>  
> +#include <linux/device.h>
>  #include <linux/iommu.h>
>  #include <linux/liveupdate.h>
>  #include <linux/kho/abi/iommu.h>
>  
>  #ifdef CONFIG_IOMMU_LIVEUPDATE
> +static inline void *dev_iommu_preserved_state(struct device *dev)
> +{
> +	struct iommu_device_ser *ser;
> +
> +	if (!dev->iommu)
> +		return NULL;
> +
> +	ser = dev->iommu->device_ser;
> +	if (ser && !ser->hdr.incoming)
> +		return ser;
> +
> +	return NULL;
> +}
> +
>  int iommu_domain_preserve(struct iommu_domain *domain, struct iommu_domain_ser **ser);
>  void iommu_domain_unpreserve(struct iommu_domain *domain);
> +int iommu_preserve_device(struct iommu_domain *domain,
> +			  struct device *dev, u64 *preserved_state);
> +void iommu_unpreserve_device(struct iommu_domain *domain, struct device *dev);
>  #else
> +static inline void *dev_iommu_preserved_state(struct device *dev)
> +{
> +	return NULL;
> +}
> +
>  static inline int iommu_domain_preserve(struct iommu_domain *domain, struct iommu_domain_ser **ser)
>  {
>  	return -EOPNOTSUPP;
> @@ -24,6 +47,16 @@ static inline int iommu_domain_preserve(struct iommu_domain *domain, struct iomm
>  static inline void iommu_domain_unpreserve(struct iommu_domain *domain)
>  {
>  }
> +
> +static inline int iommu_preserve_device(struct iommu_domain *domain,
> +					struct device *dev, u64 *preserved_state)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +static inline void iommu_unpreserve_device(struct iommu_domain *domain, struct device *dev)
> +{
> +}
>  #endif
>  
>  int iommu_liveupdate_register_flb(struct liveupdate_file_handler *handler);
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 3853a3946733..1c424b32c5fc 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -655,6 +655,10 @@ __iommu_copy_struct_to_user(const struct iommu_user_data *dst_data,
>   *               resources shared/passed to user space IOMMU instance. Associate
>   *               it with a nesting @parent_domain. It is required for driver to
>   *               set @viommu->ops pointing to its own viommu_ops
> + * @preserve_device: Preserve state of a device for liveupdate.
> + * @unpreserve_device: Unpreserve state that was preserved earlier.
> + * @preserve: Preserve state of iommu translation hardware for liveupdate.
> + * @unpreserve: Unpreserve state of iommu that was preserved earlier.
>   * @owner: Driver module providing these ops
>   * @identity_domain: An always available, always attachable identity
>   *                   translation.
> @@ -711,6 +715,13 @@ struct iommu_ops {
>  			   struct iommu_domain *parent_domain,
>  			   const struct iommu_user_data *user_data);
>  
> +#ifdef CONFIG_IOMMU_LIVEUPDATE
> +	int (*preserve_device)(struct device *dev, struct iommu_device_ser *device_ser);
> +	void (*unpreserve_device)(struct device *dev, struct iommu_device_ser *device_ser);
> +	int (*preserve)(struct iommu_device *iommu, struct iommu_hw_ser *iommu_ser);
> +	void (*unpreserve)(struct iommu_device *iommu, struct iommu_hw_ser *iommu_ser);
> +#endif
> +
>  	const struct iommu_domain_ops *default_domain_ops;
>  	struct module *owner;
>  	struct iommu_domain *identity_domain;
> @@ -806,6 +817,8 @@ struct iommu_domain_ops {
>   * @singleton_group: Used internally for drivers that have only one group
>   * @max_pasids: number of supported PASIDs
>   * @ready: set once iommu_device_register() has completed successfully
> + * @outgoing_preserved_state: preserved iommu state of outgoing kernel for
> + * liveupdate.
>   */
>  struct iommu_device {
>  	struct list_head list;
> @@ -815,6 +828,10 @@ struct iommu_device {
>  	struct iommu_group *singleton_group;
>  	u32 max_pasids;
>  	bool ready;
> +
> +#ifdef CONFIG_IOMMU_LIVEUPDATE
> +	struct iommu_hw_ser *outgoing_preserved_state;
> +#endif
>  };
>  
>  /**
> @@ -869,6 +886,9 @@ struct dev_iommu {
>  	u32				pci_32bit_workaround:1;
>  	u32				require_direct:1;
>  	u32				shadow_on_flush:1;
> +#ifdef CONFIG_IOMMU_LIVEUPDATE
> +	struct iommu_device_ser		*device_ser;
> +#endif
>  };
>  
>  int iommu_device_register(struct iommu_device *iommu,
> -- 
> 2.54.0.545.g6539524ca2-goog
>