Re: [PATCH v6 08/18] iommu: Add APIs to get iommu and device preserved state

[Baolu Lu]

On 10/25/2026 10:19 AM, Samiullah Khawaja wrote:
> 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.
>
> Reviewed-by: Pranjal Shrivastava <praan@xxxxxxxxxx>
> Signed-off-by: Samiullah Khawaja <skhawaja@xxxxxxxxxx>
> ---
>   drivers/iommu/liveupdate.c       | 88 ++++++++++++++++++++++++++++++++
>   include/linux/iommu-liveupdate.h | 70 +++++++++++++++++++++++++
>   2 files changed, 158 insertions(+)

[...]

> +
> +/**
> + * iommu_get_preserved_data() - Get preserved data for an IOMMU HW
> + * @token: Token used to preserve this IOMMU HW
> + * @type: IOMMU type in preserved state
> + *
> + * Gets the preserved state of an IOMMU HW using token and the IOMMU type.
> + *
> + * Return: struct iommu_hw_ser on success, NULL if no preserved state found.
> + */
> +struct iommu_hw_ser *iommu_get_preserved_data(u64 token, enum iommu_type_ser type)
> +{
> +	struct iommu_hw_ser *iommu_ser;
> +	struct iommu_flb_obj *flb_obj;
> +	struct kho_block_set_it it;
> +	int ret;
> +
> +	ret = iommu_liveupdate_flb_get_incoming(&flb_obj);

iommu_get_preserved_data() returns the incoming state, while
iommu_preserved_state() returns the outgoing state. The naming is
confusing.

How about using "preserved" for the old kernel before kexec and
"restored" for the new kernel after kexec? For example,
iommu_get_restored_state() would be consistent with
dev_iommu_restored_state() and iommu_domain_restored_state().

> +	if (ret)
> +		return NULL;
> +
> +	iommu_ser_set_for_each(&flb_obj->iommu_set, it, iommu_ser) {
> +		if (iommu_ser->token == token && iommu_ser->type == type)
> +			break;
> +	}
> +
> +	liveupdate_flb_put_incoming(&iommu_flb);
> +	return iommu_ser;
> +}
> +EXPORT_SYMBOL(iommu_get_preserved_data);

Why are different export macros used in the same file?

  EXPORT_SYMBOL(iommu_get_preserved_data);
  EXPORT_SYMBOL_GPL(iommu_preserve_domain);

Should these all be EXPORT_SYMBOL_GPL?

> +
>   /**
>    * iommu_preserve_domain() - Preserve an IOMMU domain across live update
>    * @domain: Domain to preserve
> diff --git a/include/linux/iommu-liveupdate.h b/include/linux/iommu-liveupdate.h
> index cdf8a82b7f1d..10fcdd41c7a1 100644
> --- a/include/linux/iommu-liveupdate.h
> +++ b/include/linux/iommu-liveupdate.h
> @@ -13,6 +13,16 @@
>   #include <linux/liveupdate.h>
>   #include <linux/kho/abi/iommu.h>
>   
> +/**
> + * iommu_preserved_device_iter_fn - Callback for iterating preserved devices
> + * @ser: Pointer to serialized device state
> + * @arg: User-defined context argument
> + *
> + * Return: 0 to continue iteration, or a negative error code to abort.
> + */
> +typedef int (*iommu_preserved_device_iter_fn)(struct iommu_device_ser *ser,
> +					      void *arg);
> +
>   #ifdef CONFIG_IOMMU_LIVEUPDATE
>   int iommu_liveupdate_register_flb(struct liveupdate_file_handler *handler);
>   void iommu_liveupdate_unregister_flb(struct liveupdate_file_handler *handler);
> @@ -52,6 +62,46 @@ static inline void *dev_iommu_preserved_state(struct device *dev)
>   	return NULL;
>   }
>   
> +/**
> + * iommu_domain_restored_state() - Get restored state of an IOMMU domain
> + * @domain: Pointer to struct iommu_domain to get restored state of.
> + *
> + * Return: Pointer to restored state on success, NULL on error.
> + */
> +static inline void *iommu_domain_restored_state(struct iommu_domain *domain)
> +{
> +	struct iommu_domain_ser *ser;
> +
> +	ser = domain->domain_ser;
> +	if (ser && (ser->hdr.flags & IOMMU_SER_FLAG_INCOMING))
> +		return ser;
> +
> +	return NULL;
> +}
> +
> +/**
> + * dev_iommu_restored_state() - Get restored state of a device
> + * @dev: Target device
> + *
> + * Return: Restored state pointer or NULL.
> + */
> +static inline void *dev_iommu_restored_state(struct device *dev)
> +{
> +	struct iommu_device_ser *ser;
> +
> +	if (!dev->iommu)
> +		return NULL;
> +
> +	ser = READ_ONCE(dev->iommu->device_ser);
> +	if (ser && (ser->hdr.flags & IOMMU_SER_FLAG_INCOMING))
> +		return ser;
> +
> +	return NULL;
> +}
> +
> +int iommu_for_each_preserved_device(iommu_preserved_device_iter_fn fn,
> +				    void *arg);
> +struct iommu_hw_ser *iommu_get_preserved_data(u64 token, enum iommu_type_ser type);
>   int iommu_preserve_domain(struct iommu_domain *domain, struct iommu_domain_ser **ser);
>   void iommu_unpreserve_domain(struct iommu_domain *domain);
>   int iommu_preserve_device(struct iommu_domain *domain,
> @@ -88,6 +138,26 @@ 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 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 iommu_hw_ser *iommu_get_preserved_data(u64 token, enum iommu_type_ser type)
> +{
> +	return NULL;
> +}
> +
>   static inline int iommu_preserve_domain(struct iommu_domain *domain, struct iommu_domain_ser **ser)
>   {
>   	return -EOPNOTSUPP;

Thanks,
baolu