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

[Samiullah Khawaja <skhawaja@google.com>]

On Fri, Oct 30, 2026 at 02:03:01PM +0800, Baolu Lu wrote:
>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@google.com>
>>Signed-off-by: Samiullah Khawaja <skhawaja@google.com>
>>---
>>  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().

Agreed. This makes it consistent. I will update this, and rename
iommu_for_each_preserved_device() the same way since it also walks the
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?

Agreed. Will update.
>
>>+
>>  /**
>>   * 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

Thanks,
Sami