Re: [PATCH 08/14] iommu: Restore and reattach preserved domains to devices

Ankit Soni
2026-03-10T05:16:58Z

On Tue, Feb 03, 2026 at 10:09:42PM +0000, Samiullah Khawaja wrote:
> Restore the preserved domains by restoring the page tables using restore
> IOMMU domain op. Reattach the preserved domain to the device during
> default domain setup. While attaching, reuse the domain ID that was used
> in the previous kernel. The context entry setup is not needed as that is
> preserved during liveupdate.
>
> Signed-off-by: Samiullah Khawaja <skhawaja@google.com>
> ---
> drivers/iommu/intel/iommu.c | 40 ++++++++++++++++++------------
> drivers/iommu/intel/iommu.h | 3 ++-
> drivers/iommu/intel/nested.c | 2 +-
> drivers/iommu/iommu.c | 47 ++++++++++++++++++++++++++++++++++--
> drivers/iommu/liveupdate.c | 31 ++++++++++++++++++++++++
> include/linux/iommu-lu.h | 8 ++++++
> 6 files changed, 112 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 8acb7f8a7627..83faad53f247 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -1029,7 +1029,8 @@ static bool first_level_by_default(struct intel_iommu *iommu)
> return true;
> }
>
> -int domain_attach_iommu(struct dmar_domain *domain, struct intel_iommu *iommu)
> +int domain_attach_iommu(struct dmar_domain *domain, struct intel_iommu *iommu,
> + int restore_did)
> {
> struct iommu_domain_info *info, *curr;
> int num, ret = -ENOSPC;
> @@ -1049,8 +1050,11 @@ int domain_attach_iommu(struct dmar_domain *domain, struct intel_iommu *iommu)
> return 0;
> }
>
> - num = ida_alloc_range(&iommu->domain_ida, IDA_START_DID,
> - cap_ndoms(iommu->cap) - 1, GFP_KERNEL);
> + if (restore_did >= 0)
> + num = restore_did;
> + else
> + num = ida_alloc_range(&iommu->domain_ida, IDA_START_DID,
> + cap_ndoms(iommu->cap) - 1, GFP_KERNEL);
> if (num < 0) {
> pr_err("%s: No free domain ids\n", iommu->name);
> goto err_unlock;
> @@ -1321,10 +1325,14 @@ static int dmar_domain_attach_device(struct dmar_domain *domain,
> {
> struct device_domain_info *info = dev_iommu_priv_get(dev);
> struct intel_iommu *iommu = info->iommu;
> + struct device_ser *device_ser = NULL;
> unsigned long flags;
> int ret;
>
> - ret = domain_attach_iommu(domain, iommu);
> + device_ser = dev_iommu_restored_state(dev);
> +
> + ret = domain_attach_iommu(domain, iommu,
> + dev_iommu_restore_did(dev, &domain->domain));
> if (ret)
> return ret;
>
> @@ -1337,16 +1345,18 @@ static int dmar_domain_attach_device(struct dmar_domain *domain,
> if (dev_is_real_dma_subdevice(dev))
> return 0;
>
> - if (!sm_supported(iommu))
> - ret = domain_context_mapping(domain, dev);
> - else if (intel_domain_is_fs_paging(domain))
> - ret = domain_setup_first_level(iommu, domain, dev,
> - IOMMU_NO_PASID, NULL);
> - else if (intel_domain_is_ss_paging(domain))
> - ret = domain_setup_second_level(iommu, domain, dev,
> - IOMMU_NO_PASID, NULL);
> - else if (WARN_ON(true))
> - ret = -EINVAL;
> + if (!device_ser) {
> + if (!sm_supported(iommu))
> + ret = domain_context_mapping(domain, dev);
> + else if (intel_domain_is_fs_paging(domain))
> + ret = domain_setup_first_level(iommu, domain, dev,
> + IOMMU_NO_PASID, NULL);
> + else if (intel_domain_is_ss_paging(domain))
> + ret = domain_setup_second_level(iommu, domain, dev,
> + IOMMU_NO_PASID, NULL);
> + else if (WARN_ON(true))
> + ret = -EINVAL;
> + }
>
> if (ret)
> goto out_block_translation;
> @@ -3630,7 +3640,7 @@ domain_add_dev_pasid(struct iommu_domain *domain,
> if (!dev_pasid)
> return ERR_PTR(-ENOMEM);
>
> - ret = domain_attach_iommu(dmar_domain, iommu);
> + ret = domain_attach_iommu(dmar_domain, iommu, -1);
> if (ret)
> goto out_free;
>
> diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
> index d7bf63aff17d..057bd6035d85 100644
> --- a/drivers/iommu/intel/iommu.h
> +++ b/drivers/iommu/intel/iommu.h
> @@ -1174,7 +1174,8 @@ void __iommu_flush_iotlb(struct intel_iommu *iommu, u16 did, u64 addr,
> */
> #define QI_OPT_WAIT_DRAIN BIT(0)
>
> -int domain_attach_iommu(struct dmar_domain *domain, struct intel_iommu *iommu);
> +int domain_attach_iommu(struct dmar_domain *domain, struct intel_iommu *iommu,
> + int restore_did);
> void domain_detach_iommu(struct dmar_domain *domain, struct intel_iommu *iommu);
> void device_block_translation(struct device *dev);
> int paging_domain_compatible(struct iommu_domain *domain, struct device *dev);
> diff --git a/drivers/iommu/intel/nested.c b/drivers/iommu/intel/nested.c
> index a3fb8c193ca6..4fed9f5981e5 100644
> --- a/drivers/iommu/intel/nested.c
> +++ b/drivers/iommu/intel/nested.c
> @@ -40,7 +40,7 @@ static int intel_nested_attach_dev(struct iommu_domain *domain,
> return ret;
> }
>
> - ret = domain_attach_iommu(dmar_domain, iommu);
> + ret = domain_attach_iommu(dmar_domain, iommu, -1);
> if (ret) {
> dev_err_ratelimited(dev, "Failed to attach domain to iommu\n");
> return ret;
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index c0632cb5b570..8103b5372364 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -18,6 +18,7 @@
> #include <linux/errno.h>
> #include <linux/host1x_context_bus.h>
> #include <linux/iommu.h>
> +#include <linux/iommu-lu.h>
> #include <linux/iommufd.h>
> #include <linux/idr.h>
> #include <linux/err.h>
> @@ -489,6 +490,10 @@ static int iommu_init_device(struct device *dev)
> goto err_free;
> }
>
> +#ifdef CONFIG_IOMMU_LIVEUPDATE
> + dev->iommu->device_ser = iommu_get_device_preserved_data(dev);
> +#endif
> +
> iommu_dev = ops->probe_device(dev);
> if (IS_ERR(iommu_dev)) {
> ret = PTR_ERR(iommu_dev);
> @@ -2149,6 +2154,13 @@ static int __iommu_attach_device(struct iommu_domain *domain,
> ret = domain->ops->attach_dev(domain, dev, old);
> if (ret)
> return ret;
> +
> +#ifdef CONFIG_IOMMU_LIVEUPDATE
> + /* The associated state can be unset once restored. */
> + if (dev_iommu_restored_state(dev))
> + WRITE_ONCE(dev->iommu->device_ser, NULL);
> +#endif
> +
> dev->iommu->attach_deferred = 0;
> trace_attach_device_to_domain(dev);
> return 0;
> @@ -3061,6 +3073,34 @@ int iommu_fwspec_add_ids(struct device *dev, const u32 *ids, int num_ids)
> }
> EXPORT_SYMBOL_GPL(iommu_fwspec_add_ids);
>
> +static struct iommu_domain *__iommu_group_maybe_restore_domain(struct iommu_group *group)
> +{
> + struct device_ser *device_ser;
> + struct iommu_domain *domain;
> + struct device *dev;
> +
> + dev = iommu_group_first_dev(group);
> + if (!dev_is_pci(dev))
> + return NULL;
> +
> + device_ser = dev_iommu_restored_state(dev);
> + if (!device_ser)
> + return NULL;
> +
> + domain = iommu_restore_domain(dev, device_ser);
> + if (WARN_ON(IS_ERR(domain)))
> + return NULL;
> +
> + /*
> + * The group is owned by the entity (a preserved iommufd) that provided
> + * this token in the previous kernel. It will be used to reclaim it
> + * later.
> + */
> + group->owner = (void *)device_ser->token;
> + group->owner_cnt = 1;
> + return domain;
> +}
> +
> /**
> * iommu_setup_default_domain - Set the default_domain for the group
> * @group: Group to change
> @@ -3075,8 +3115,8 @@ static int iommu_setup_default_domain(struct iommu_group *group,
> int target_type)
> {
> struct iommu_domain *old_dom = group->default_domain;
> + struct iommu_domain *dom, *restored_domain;
> struct group_device *gdev;
> - struct iommu_domain *dom;
> bool direct_failed;
> int req_type;
> int ret;
> @@ -3120,6 +3160,9 @@ static int iommu_setup_default_domain(struct iommu_group *group,
> /* We must set default_domain early for __iommu_device_set_domain */
> group->default_domain = dom;
> if (!group->domain) {
> + restored_domain = __iommu_group_maybe_restore_domain(group);
> + if (!restored_domain)
> + restored_domain = dom;
> /*
> * Drivers are not allowed to fail the first domain attach.
> * The only way to recover from this is to fail attaching the
> @@ -3127,7 +3170,7 @@ static int iommu_setup_default_domain(struct iommu_group *group,
> * in group->default_domain so it is freed after.
> */
> ret = __iommu_group_set_domain_internal(
> - group, dom, IOMMU_SET_DOMAIN_MUST_SUCCEED);
> + group, restored_domain, IOMMU_SET_DOMAIN_MUST_SUCCEED);
> if (WARN_ON(ret))
> goto out_free_old;
> } else {
> diff --git a/drivers/iommu/liveupdate.c b/drivers/iommu/liveupdate.c
> index 83eb609b3fd7..6b211436ad25 100644
> --- a/drivers/iommu/liveupdate.c
> +++ b/drivers/iommu/liveupdate.c
> @@ -501,3 +501,34 @@ void iommu_unpreserve_device(struct iommu_domain *domain, struct device *dev)
>
> iommu_unpreserve_locked(iommu->iommu_dev);
> }
> +
> +struct iommu_domain *iommu_restore_domain(struct device *dev, struct device_ser *ser)
> +{
> + struct iommu_domain_ser *domain_ser;
> + struct iommu_lu_flb_obj *flb_obj;
> + struct iommu_domain *domain;
> + int ret;
> +
> + domain_ser = __va(ser->domain_iommu_ser.domain_phys);
> +
> + ret = liveupdate_flb_get_incoming(&iommu_flb, (void **)&flb_obj);
> + if (ret)
> + return ERR_PTR(ret);
> +
> + guard(mutex)(&flb_obj->lock);
> + if (domain_ser->restored_domain)
> + return domain_ser->restored_domain;
> +
> + domain_ser->obj.incoming = true;
> + domain = iommu_paging_domain_alloc(dev);
> + if (IS_ERR(domain))
> + return domain;
> +
> + ret = domain->ops->restore(domain, domain_ser);
> + if (ret)

'domain' will leak here.

> + return ERR_PTR(ret);
> +
> + domain->preserved_state = domain_ser;
> + domain_ser->restored_domain = domain;
> + return domain;
> +}
> diff --git a/include/linux/iommu-lu.h b/include/linux/iommu-lu.h
> index 48c07514a776..4879abaf83d3 100644
> --- a/include/linux/iommu-lu.h
> +++ b/include/linux/iommu-lu.h
> @@ -65,6 +65,8 @@ static inline int dev_iommu_restore_did(struct device *dev, struct iommu_domain
> return -1;
> }
>
> +struct iommu_domain *iommu_restore_domain(struct device *dev,
> + struct device_ser *ser);
> 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);
> @@ -95,6 +97,12 @@ static inline void *iommu_domain_restored_state(struct iommu_domain *domain)
> return NULL;
> }
>
> +static inline struct iommu_domain *iommu_restore_domain(struct device *dev,
> + struct device_ser *ser)
> +{
> + return NULL;
> +}
> +
> static inline int iommu_for_each_preserved_device(iommu_preserved_device_iter_fn fn, void *arg)
> {
> return -EOPNOTSUPP;
> --
> 2.53.0.rc2.204.g2597b5adb4-goog
>