Re: [PATCH v2 10/16] iommu: Restore and reattach preserved domains to devices
From: Baolu Lu
Date: Thu May 07 2026 - 09:59:19 EST
On 4/28/2026 1:56 AM, 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@xxxxxxxxxx>
---
drivers/iommu/intel/iommu.c | 49 ++++++++++++++------
drivers/iommu/intel/iommu.h | 3 +-
drivers/iommu/intel/nested.c | 2 +-
drivers/iommu/iommu.c | 61 ++++++++++++++++++++++++-
drivers/iommu/liveupdate.c | 78 ++++++++++++++++++++++++++++++++
include/linux/iommu-liveupdate.h | 50 ++++++++++++++++++++
6 files changed, 224 insertions(+), 19 deletions(-)
Please split the changes in the Intel iommu driver and the iommu core
into different patches.
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 4118a0861f38..b90757164cd8 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1031,7 +1031,8 @@ 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)
How about using a new helper for restored domain? For example,
int domain_reattach_iommu(...)
or
int domain_restore_iommu(...)
{
struct iommu_domain_info *info, *curr;
int num, ret = -ENOSPC;
@@ -1051,8 +1052,11 @@ 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 >= IDA_START_DID)
+ num = restore_did;
For a preserved domain ID, do we need to check whether it has been
reserved from the ida pool?
+ 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;
@@ -1320,10 +1324,14 @@ 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));
What is the expected behavior if there is a mismatch between the
restored state and the availability of a domain ID? Specifically, if
device_ser is found but dev_iommu_restore_did() fails (returns -1), how
should the driver proceed in that case?
if (ret)
return ret;
@@ -1336,16 +1344,18 @@ 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;
@@ -3170,6 +3180,15 @@ int paging_domain_compatible(struct iommu_domain *domain, struct device *dev)
struct intel_iommu *iommu = info->iommu;
int ret = -EINVAL;
+#ifdef CONFIG_IOMMU_LIVEUPDATE
+ /*
+ * Restored IOMMU domains are already attached to the device and can
+ * only be freed. So no need to check the compatibility.
+ */
+ if (iommu_domain_restored_state(domain))
+ return 0;
+#endif
+
if (intel_domain_is_fs_paging(dmar_domain))
ret = paging_domain_compatible_first_stage(dmar_domain, iommu);
else if (intel_domain_is_ss_paging(dmar_domain))
@@ -3647,7 +3666,7 @@ 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 b0ec0b471a43..8e37acf7de12 100644
--- a/drivers/iommu/intel/iommu.h
+++ b/drivers/iommu/intel/iommu.h
@@ -1182,7 +1182,8 @@ 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 2b979bec56ce..6e13f697b463 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;
Thanks,
baolu