Re: [PATCH 02/14] iommu: Implement IOMMU core liveupdate skeleton

[Pranjal Shrivastava <praan@google.com>]

On Tue, Feb 03, 2026 at 10:09:36PM +0000, Samiullah Khawaja wrote:
> Add IOMMU domain ops that can be implemented by the IOMMU drivers if
> they support IOMMU domain preservation across liveupdate. The new IOMMU
> domain preserve, unpreserve and restore APIs call these ops to perform
> respective live update operations.
> 
> Similarly 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. The device can only be
> preserved if the attached iommu domain is preserved and the associated
> iommu supports preservation.
> 
> The preserved state of the device and IOMMU needs to be fetched during
> shutdown and boot in the next kernel. Add APIs that can be used to fetch
> the preserved state of a device and IOMMU. The APIs will only be used
> during shutdown and after liveupdate so no locking needed.
> 
> Signed-off-by: Samiullah Khawaja <skhawaja@google.com>
> ---
>  drivers/iommu/iommu.c      |   3 +
>  drivers/iommu/liveupdate.c | 326 +++++++++++++++++++++++++++++++++++++
>  include/linux/iommu-lu.h   | 119 ++++++++++++++
>  include/linux/iommu.h      |  32 ++++
>  4 files changed, 480 insertions(+)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 4926a43118e6..c0632cb5b570 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -389,6 +389,9 @@ static struct dev_iommu *dev_iommu_get(struct device *dev)
>  
>  	mutex_init(&param->lock);
>  	dev->iommu = param;
> +#ifdef CONFIG_IOMMU_LIVEUPDATE
> +	dev->iommu->device_ser = NULL;
> +#endif
>  	return param;
>  }
>  
> diff --git a/drivers/iommu/liveupdate.c b/drivers/iommu/liveupdate.c
> index 6189ba32ff2c..83eb609b3fd7 100644
> --- a/drivers/iommu/liveupdate.c
> +++ b/drivers/iommu/liveupdate.c
> @@ -11,6 +11,7 @@
>  #include <linux/liveupdate.h>
>  #include <linux/iommu-lu.h>
>  #include <linux/iommu.h>
> +#include <linux/pci.h>
>  #include <linux/errno.h>
>  
>  static void iommu_liveupdate_restore_objs(u64 next)
> @@ -175,3 +176,328 @@ int iommu_liveupdate_unregister_flb(struct liveupdate_file_handler *handler)
>  	return liveupdate_unregister_flb(handler, &iommu_flb);
>  }
>  EXPORT_SYMBOL(iommu_liveupdate_unregister_flb);
> +
> +int iommu_for_each_preserved_device(iommu_preserved_device_iter_fn fn,
> +				    void *arg)
> +{
> +	struct iommu_lu_flb_obj *obj;
> +	struct devices_ser *devices;
> +	int ret, i, idx;
> +
> +	ret = liveupdate_flb_get_incoming(&iommu_flb, (void **)&obj);
> +	if (ret)
> +		return -ENOENT;
> +
> +	devices = __va(obj->ser->devices_phys);
> +	for (i = 0, idx = 0; i < obj->ser->nr_devices; ++i, ++idx) {
> +		if (idx >= MAX_DEVICE_SERS) {
> +			devices = __va(devices->objs.next_objs);
> +			idx = 0;
> +		}
> +
> +		if (devices->devices[idx].obj.deleted)
> +			continue;
> +
> +		ret = fn(&devices->devices[idx], arg);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(iommu_for_each_preserved_device);
> +
> +static inline bool device_ser_match(struct device_ser *match,
> +				    struct pci_dev *pdev)
> +{
> +	return match->devid == pci_dev_id(pdev) && match->pci_domain == pci_domain_nr(pdev->bus);
> +}
> +
> +struct device_ser *iommu_get_device_preserved_data(struct device *dev)
> +{
> +	struct iommu_lu_flb_obj *obj;
> +	struct devices_ser *devices;
> +	int ret, i, idx;
> +
> +	if (!dev_is_pci(dev))
> +		return NULL;
> +
> +	ret = liveupdate_flb_get_incoming(&iommu_flb, (void **)&obj);
> +	if (ret)
> +		return NULL;
> +
> +	devices = __va(obj->ser->devices_phys);
> +	for (i = 0, idx = 0; i < obj->ser->nr_devices; ++i, ++idx) {
> +		if (idx >= MAX_DEVICE_SERS) {
> +			devices = __va(devices->objs.next_objs);
> +			idx = 0;
> +		}
> +
> +		if (devices->devices[idx].obj.deleted)
> +			continue;
> +
> +		if (device_ser_match(&devices->devices[idx], to_pci_dev(dev))) {
> +			devices->devices[idx].obj.incoming = true;
> +			return &devices->devices[idx];
> +		}
> +	}
> +
> +	return NULL;
> +}
> +EXPORT_SYMBOL(iommu_get_device_preserved_data);
> +
> +struct iommu_ser *iommu_get_preserved_data(u64 token, enum iommu_lu_type type)
> +{
> +	struct iommu_lu_flb_obj *obj;
> +	struct iommus_ser *iommus;
> +	int ret, i, idx;
> +
> +	ret = liveupdate_flb_get_incoming(&iommu_flb, (void **)&obj);
> +	if (ret)
> +		return NULL;
> +
> +	iommus = __va(obj->ser->iommus_phys);
> +	for (i = 0, idx = 0; i < obj->ser->nr_iommus; ++i, ++idx) {
> +		if (idx >= MAX_IOMMU_SERS) {
> +			iommus = __va(iommus->objs.next_objs);
> +			idx = 0;
> +		}
> +
> +		if (iommus->iommus[idx].obj.deleted)
> +			continue;
> +
> +		if (iommus->iommus[idx].token == token &&
> +		    iommus->iommus[idx].type == type)
> +			return &iommus->iommus[idx];
> +	}
> +
> +	return NULL;
> +}
> +EXPORT_SYMBOL(iommu_get_preserved_data);
> +
> +static int reserve_obj_ser(struct iommu_objs_ser **objs_ptr, u64 max_objs)

Isn't this more of an "insert" / "populate" / write_ser_entry? We can
rename it to something like iommu_ser_push_entry / iommu_ser_write_entry

> +{
> +	struct iommu_objs_ser *next_objs, *objs = *objs_ptr;

Not loving these names :(

TBH, the reserve_obj_ser function isn't too readable, esp. with all the
variable names, here and in the lu header.. I've had to go back n forth
to the first patch. For example, here next_objs can be next_objs_page &
objs can be curr_page. (PTAL at my reply on PATCH 01 about renaming).

> +	int idx;
> +
> +	if (objs->nr_objs == max_objs) {
> +		next_objs = kho_alloc_preserve(PAGE_SIZE);
> +		if (IS_ERR(next_objs))
> +			return PTR_ERR(next_objs);
> +
> +		objs->next_objs = virt_to_phys(next_objs);
> +		objs = next_objs;
> +		*objs_ptr = objs;
> +		objs->nr_objs = 0;
> +		objs->next_objs = 0;

This seems redundant, no need to zero these out, kho_alloc_preserve 
passes __GFP_ZERO to folio_alloc [1], which should z-alloc the pages.

> +	}
> +
> +	idx = objs->nr_objs++;
> +	return idx;
> +}

Just to give a mental model to fellow reviewers, here's how this is laid
out:

----------------------------------------------------------------------
[ PAGE START ]                                                       |
----------------------------------------------------------------------
| iommu_objs_ser (The Page Header)                                   |
|   - next_objs: 0x0000 (End of the page-chain)                      |
|   - nr_objs: 2                                                     |
----------------------------------------------------------------------
| ITEM 0: iommu_domain_ser                                           |
|   [ iommu_obj_ser (The entry header) ]                             |
|     - idx: 0                                                       |
|     - ref_count: 1                                                 |
|     - deleted: 0                                                   |
|   [ Domain Data ]                                                  |
----------------------------------------------------------------------
| ITEM 1: iommu_domain_ser                                           |
|   [ iommu_obj_ser (The Price Tag) ]                                |
|     - idx: 1                                                       |
|     - ref_count: 1                                                 |
|     - deleted: 0                                                   |
|   [ Domain Data ]                                                  |
----------------------------------------------------------------------
| ... (Empty space for more domains) ...                             |
|                                                                    |
----------------------------------------------------------------------
[ PAGE END ]                                                         |
----------------------------------------------------------------------

> +
> +int iommu_domain_preserve(struct iommu_domain *domain, struct iommu_domain_ser **ser)
> +{
> +	struct iommu_domain_ser *domain_ser;
> +	struct iommu_lu_flb_obj *flb_obj;
> +	int idx, ret;
> +
> +	if (!domain->ops->preserve)
> +		return -EOPNOTSUPP;
> +
> +	ret = liveupdate_flb_get_outgoing(&iommu_flb, (void **)&flb_obj);
> +	if (ret)
> +		return ret;
> +
> +	guard(mutex)(&flb_obj->lock);
> +	idx = reserve_obj_ser((struct iommu_objs_ser **)&flb_obj->iommu_domains,
> +			      MAX_IOMMU_DOMAIN_SERS);
> +	if (idx < 0)
> +		return idx;
> +
> +	domain_ser = &flb_obj->iommu_domains->iommu_domains[idx];

This is slightly less-readable as well, I understand we're trying to:

iommu_domains_ser -> iommu_domain_ser[idx] but the same name
(iommu_domains) makes it difficult to read.. we should rename this as:

&flb_obj->iommu_domains_page->domain_entries[idx] or something for
better readability..

Also, let's add a comment explaining that reserve_obj_ser actually
advances the flb_obj ptr when necessary..

IIUC, we start with PAGE 0 initially, store it's phys in the
iommu_flb_preserve op (the iommu_ser_phys et al) & then we go on 
alloc-ing more pages and keep storing the "current" active page with the
liveupdate core. Now when we jump into the new kernel, we read the
ser_phys and then follow the page chain, right?

> +	idx = flb_obj->ser->nr_domains++;
> +	domain_ser->obj.idx = idx;
> +	domain_ser->obj.ref_count = 1;
> +
> +	ret = domain->ops->preserve(domain, domain_ser);
> +	if (ret) {
> +		domain_ser->obj.deleted = true;
> +		return ret;
> +	}
> +
> +	domain->preserved_state = domain_ser;
> +	*ser = domain_ser;
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_domain_preserve);
> +
> +void iommu_domain_unpreserve(struct iommu_domain *domain)
> +{
> +	struct iommu_domain_ser *domain_ser;
> +	struct iommu_lu_flb_obj *flb_obj;
> +	int ret;
> +
> +	if (!domain->ops->unpreserve)
> +		return;
> +
> +	ret = liveupdate_flb_get_outgoing(&iommu_flb, (void **)&flb_obj);
> +	if (ret)
> +		return;
> +
> +	guard(mutex)(&flb_obj->lock);
> +
> +	/*
> +	 * There is no check for attached devices here. The correctness relies
> +	 * on the Live Update Orchestrator's session lifecycle. All resources
> +	 * (iommufd, vfio devices) are preserved within a single session. If the
> +	 * session is torn down, the .unpreserve callbacks for all files will be
> +	 * invoked, ensuring a consistent cleanup without needing explicit
> +	 * refcounting for the serialized objects here.
> +	 */
> +	domain_ser = domain->preserved_state;
> +	domain->ops->unpreserve(domain, domain_ser);
> +	domain_ser->obj.deleted = true;
> +	domain->preserved_state = NULL;
> +}
> +EXPORT_SYMBOL_GPL(iommu_domain_unpreserve);
> +
> +static int iommu_preserve_locked(struct iommu_device *iommu)
> +{
> +	struct iommu_lu_flb_obj *flb_obj;
> +	struct iommu_ser *iommu_ser;
> +	int idx, ret;
> +
> +	if (!iommu->ops->preserve)
> +		return -EOPNOTSUPP;
> +
> +	if (iommu->outgoing_preserved_state) {
> +		iommu->outgoing_preserved_state->obj.ref_count++;
> +		return 0;
> +	}
> +
> +	ret = liveupdate_flb_get_outgoing(&iommu_flb, (void **)&flb_obj);
> +	if (ret)
> +		return ret;
> +
> +	idx = reserve_obj_ser((struct iommu_objs_ser **)&flb_obj->iommus,
> +			      MAX_IOMMU_SERS);
> +	if (idx < 0)
> +		return idx;
> +
> +	iommu_ser = &flb_obj->iommus->iommus[idx];
> +	idx = flb_obj->ser->nr_iommus++;
> +	iommu_ser->obj.idx = idx;
> +	iommu_ser->obj.ref_count = 1;
> +
> +	ret = iommu->ops->preserve(iommu, iommu_ser);
> +	if (ret)
> +		iommu_ser->obj.deleted = true;
> +
> +	iommu->outgoing_preserved_state = iommu_ser;
> +	return ret;
> +}
> +
> +static void iommu_unpreserve_locked(struct iommu_device *iommu)
> +{
> +	struct iommu_ser *iommu_ser = iommu->outgoing_preserved_state;
> +
> +	iommu_ser->obj.ref_count--;
> +	if (iommu_ser->obj.ref_count)
> +		return;
> +
> +	iommu->outgoing_preserved_state = NULL;
> +	iommu->ops->unpreserve(iommu, iommu_ser);
> +	iommu_ser->obj.deleted = true;
> +}
> +
> +int iommu_preserve_device(struct iommu_domain *domain,
> +			  struct device *dev, u64 token)
> +{
> +	struct iommu_lu_flb_obj *flb_obj;
> +	struct device_ser *device_ser;
> +	struct dev_iommu *iommu;
> +	struct pci_dev *pdev;
> +	int ret, idx;
> +
> +	if (!dev_is_pci(dev))
> +		return -EOPNOTSUPP;
> +
> +	if (!domain->preserved_state)
> +		return -EINVAL;
> +
> +	pdev = to_pci_dev(dev);
> +	iommu = dev->iommu;
> +	if (!iommu->iommu_dev->ops->preserve_device ||
> +	    !iommu->iommu_dev->ops->preserve)
> +		return -EOPNOTSUPP;
> +
> +	ret = liveupdate_flb_get_outgoing(&iommu_flb, (void **)&flb_obj);
> +	if (ret)
> +		return ret;
> +
> +	guard(mutex)(&flb_obj->lock);
> +	idx = reserve_obj_ser((struct iommu_objs_ser **)&flb_obj->devices,
> +			      MAX_DEVICE_SERS);
> +	if (idx < 0)
> +		return idx;
> +
> +	device_ser = &flb_obj->devices->devices[idx];
> +	idx = flb_obj->ser->nr_devices++;
> +	device_ser->obj.idx = idx;
> +	device_ser->obj.ref_count = 1;
> +
> +	ret = iommu_preserve_locked(iommu->iommu_dev);
> +	if (ret) {
> +		device_ser->obj.deleted = true;
> +		return ret;
> +	}
> +
> +	device_ser->domain_iommu_ser.domain_phys = __pa(domain->preserved_state);
> +	device_ser->domain_iommu_ser.iommu_phys = __pa(iommu->iommu_dev->outgoing_preserved_state);
> +	device_ser->devid = pci_dev_id(pdev);
> +	device_ser->pci_domain = pci_domain_nr(pdev->bus);
> +	device_ser->token = token;
> +
> +	ret = iommu->iommu_dev->ops->preserve_device(dev, device_ser);
> +	if (ret) {
> +		device_ser->obj.deleted = true;
> +		iommu_unpreserve_locked(iommu->iommu_dev);
> +		return ret;
> +	}
> +
> +	dev->iommu->device_ser = device_ser;
> +	return 0;
> +}
> +
> +void iommu_unpreserve_device(struct iommu_domain *domain, struct device *dev)
> +{
> +	struct iommu_lu_flb_obj *flb_obj;
> +	struct device_ser *device_ser;
> +	struct dev_iommu *iommu;
> +	struct pci_dev *pdev;
> +	int ret;
> +
> +	if (!dev_is_pci(dev))
> +		return;
> +
> +	pdev = to_pci_dev(dev);
> +	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);
> +	device_ser = dev_iommu_preserved_state(dev);
> +	if (WARN_ON(!device_ser))
> +		return;
> +
> +	iommu->iommu_dev->ops->unpreserve_device(dev, device_ser);
> +	dev->iommu->device_ser = NULL;
> +
> +	iommu_unpreserve_locked(iommu->iommu_dev);
> +}

I'm wondering ig we should guard these APIs against accidental or 
potential abuse by other in-kernel drivers. Since the Live Update 
Orchestrator (LUO) is architecturally designed around user-space 
driven sequences (IOCTLs, specific mutex ordering, etc.), for now.

Since the header-file is also under include/linux, we should avoid any
possibility where we end up having drivers depending on these API.
We could add a check based on dma owner:

+	/* Only devices explicitly claimed by a user-space driver 
+	 * (VFIO/IOMMUFD) are eligible for Live Update preservation.
+	 */
+	if (!iommu_dma_owner_claimed(dev))
+		return -EPERM;

This should ensure we aren't creating 'zombie' preserved states for 
devices not managed by IOMMUFD/VFIO.


> diff --git a/include/linux/iommu-lu.h b/include/linux/iommu-lu.h
> index 59095d2f1bb2..48c07514a776 100644
> --- a/include/linux/iommu-lu.h
> +++ b/include/linux/iommu-lu.h
> @@ -8,9 +8,128 @@
>  #ifndef _LINUX_IOMMU_LU_H
>  #define _LINUX_IOMMU_LU_H
>  
> +#include <linux/device.h>
> +#include <linux/iommu.h>
>  #include <linux/liveupdate.h>
>  #include <linux/kho/abi/iommu.h>
>  
> +typedef int (*iommu_preserved_device_iter_fn)(struct device_ser *ser,
> +					      void *arg);
> +#ifdef CONFIG_IOMMU_LIVEUPDATE
> +static inline void *dev_iommu_preserved_state(struct device *dev)
> +{
> +	struct device_ser *ser;
> +
> +	if (!dev->iommu)
> +		return NULL;
> +
> +	ser = dev->iommu->device_ser;
> +	if (ser && !ser->obj.incoming)
> +		return ser;
> +
> +	return NULL;
> +}
> +
> +static inline void *dev_iommu_restored_state(struct device *dev)
> +{
> +	struct device_ser *ser;
> +
> +	if (!dev->iommu)
> +		return NULL;
> +
> +	ser = dev->iommu->device_ser;
> +	if (ser && ser->obj.incoming)
> +		return ser;
> +
> +	return NULL;
> +}
> +
> +static inline void *iommu_domain_restored_state(struct iommu_domain *domain)
> +{
> +	struct iommu_domain_ser *ser;
> +
> +	ser = domain->preserved_state;
> +	if (ser && ser->obj.incoming)
> +		return ser;
> +
> +	return NULL;
> +}
> +
> +static inline int dev_iommu_restore_did(struct device *dev, struct iommu_domain *domain)
> +{
> +	struct device_ser *ser = dev_iommu_restored_state(dev);
> +
> +	if (ser && iommu_domain_restored_state(domain))
> +		return ser->domain_iommu_ser.did;
> +
> +	return -1;
> +}
> +
> +int iommu_for_each_preserved_device(iommu_preserved_device_iter_fn fn,
> +				    void *arg);
> +struct device_ser *iommu_get_device_preserved_data(struct device *dev);
> +struct iommu_ser *iommu_get_preserved_data(u64 token, enum iommu_lu_type type);
> +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 token);
> +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 void *dev_iommu_restored_state(struct device *dev)
> +{
> +	return NULL;
> +}
> +
> +static inline int dev_iommu_restore_did(struct device *dev, struct iommu_domain *domain)
> +{
> +	return -1;
> +}
> +
> +static inline void *iommu_domain_restored_state(struct iommu_domain *domain)
> +{
> +	return NULL;
> +}
> +
> +static inline int iommu_for_each_preserved_device(iommu_preserved_device_iter_fn fn, void *arg)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +static inline struct device_ser *iommu_get_device_preserved_data(struct device *dev)
> +{
> +	return NULL;
> +}
> +
> +static inline struct iommu_ser *iommu_get_preserved_data(u64 token, enum iommu_lu_type type)
> +{
> +	return NULL;
> +}
> +
> +static inline int iommu_domain_preserve(struct iommu_domain *domain, struct iommu_domain_ser **ser)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +static inline void iommu_domain_unpreserve(struct iommu_domain *domain)
> +{
> +}
> +
> +static inline int iommu_preserve_device(struct iommu_domain *domain,
> +					struct device *dev, u64 token)
> +{
> +	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);
>  int iommu_liveupdate_unregister_flb(struct liveupdate_file_handler *handler);
>  
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 54b8b48c762e..bd949c1ce7c5 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -14,6 +14,8 @@
>  #include <linux/err.h>
>  #include <linux/of.h>
>  #include <linux/iova_bitmap.h>
> +#include <linux/atomic.h>
> +#include <linux/kho/abi/iommu.h>
>  #include <uapi/linux/iommufd.h>
>  
>  #define IOMMU_READ	(1 << 0)
> @@ -248,6 +250,10 @@ struct iommu_domain {
>  			struct list_head next;
>  		};
>  	};
> +
> +#ifdef CONFIG_IOMMU_LIVEUPDATE
> +	struct iommu_domain_ser *preserved_state;
> +#endif
>  };
>  
>  static inline bool iommu_is_dma_domain(struct iommu_domain *domain)
> @@ -647,6 +653,10 @@ __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.
> @@ -703,6 +713,11 @@ struct iommu_ops {
>  			   struct iommu_domain *parent_domain,
>  			   const struct iommu_user_data *user_data);
>  
> +	int (*preserve_device)(struct device *dev, struct device_ser *device_ser);
> +	void (*unpreserve_device)(struct device *dev, struct device_ser *device_ser);

Nit: Let's move the _device ops under the comment:
`/* Per device IOMMU features */`

> +	int (*preserve)(struct iommu_device *iommu, struct iommu_ser *iommu_ser);
> +	void (*unpreserve)(struct iommu_device *iommu, struct iommu_ser *iommu_ser);
> +

I'm wondering if there's any benefit to add these ops under a #ifdef ?

>  	const struct iommu_domain_ops *default_domain_ops;
>  	struct module *owner;
>  	struct iommu_domain *identity_domain;
> @@ -749,6 +764,11 @@ struct iommu_ops {
>   *                           specific mechanisms.
>   * @set_pgtable_quirks: Set io page table quirks (IO_PGTABLE_QUIRK_*)
>   * @free: Release the domain after use.
> + * @preserve: Preserve the iommu domain for liveupdate.
> + *            Returns 0 on success, a negative errno on failure.
> + * @unpreserve: Unpreserve the iommu domain that was preserved earlier.
> + * @restore: Restore the iommu domain after liveupdate.
> + *           Returns 0 on success, a negative errno on failure.
>   */
>  struct iommu_domain_ops {
>  	int (*attach_dev)(struct iommu_domain *domain, struct device *dev,
> @@ -779,6 +799,9 @@ struct iommu_domain_ops {
>  				  unsigned long quirks);
>  
>  	void (*free)(struct iommu_domain *domain);
> +	int (*preserve)(struct iommu_domain *domain, struct iommu_domain_ser *ser);
> +	void (*unpreserve)(struct iommu_domain *domain, struct iommu_domain_ser *ser);
> +	int (*restore)(struct iommu_domain *domain, struct iommu_domain_ser *ser);
>  };
>  
>  /**
> @@ -790,6 +813,8 @@ 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;
> @@ -799,6 +824,10 @@ struct iommu_device {
>  	struct iommu_group *singleton_group;
>  	u32 max_pasids;
>  	bool ready;
> +
> +#ifdef CONFIG_IOMMU_LIVEUPDATE
> +	struct iommu_ser *outgoing_preserved_state;
> +#endif
>  };
>  
>  /**
> @@ -853,6 +882,9 @@ struct dev_iommu {
>  	u32				pci_32bit_workaround:1;
>  	u32				require_direct:1;
>  	u32				shadow_on_flush:1;
> +#ifdef CONFIG_IOMMU_LIVEUPDATE
> +	struct device_ser		*device_ser;
> +#endif
>  };
>  
>  int iommu_device_register(struct iommu_device *iommu,

Thanks,
Praan

[1] https://elixir.bootlin.com/linux/v7.0-rc3/source/kernel/liveupdate/kexec_handover.c#L1182