Re: [PATCH v6 05/18] iommu: Implement device and IOMMU HW preservation
From: Baolu Lu
Date: Sat Oct 31 2026 - 01:34:30 EST
On 10/31/2026 9:45 AM, Samiullah Khawaja wrote:
On Fri, Oct 30, 2026 at 01:12:31PM +0800, Baolu Lu wrote:
On 10/25/2026 10:19 AM, Samiullah Khawaja wrote:
Add IOMMU ops to preserve/unpreserve the device state handled by the
IOMMU driver. This is IOMMU specific state of the device that needs to
be preserved for liveupdate. These ops 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 as dependency.
Signed-off-by: Samiullah Khawaja <skhawaja@xxxxxxxxxx>
---
drivers/iommu/iommu-priv.h | 2 +
drivers/iommu/iommu.c | 72 +++++++++++-
drivers/iommu/liveupdate.c | 189 +++++++++++++++++++++++++++++++
include/linux/iommu-liveupdate.h | 76 +++++++++++++
include/linux/iommu.h | 33 ++++++
5 files changed, 371 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/iommu-priv.h b/drivers/iommu/iommu-priv.h
index 1f9f886b2c10..6b0ef210b32f 100644
--- a/drivers/iommu/iommu-priv.h
+++ b/drivers/iommu/iommu-priv.h
@@ -21,6 +21,8 @@ static inline const struct iommu_ops *dev_iommu_ops(struct device *dev)
void dev_iommu_free(struct device *dev);
+bool iommu_group_is_singleton(struct iommu_group *group);
+
const struct iommu_ops *iommu_ops_from_fwnode(const struct fwnode_handle *fwnode);
static inline const struct iommu_ops *iommu_fwspec_ops(struct iommu_fwspec *fwspec)
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index b486b8bbd1fc..a66363789ca9 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-liveupdate.h>
#include <linux/iommufd.h>
#include <linux/idr.h>
#include <linux/err.h>
@@ -328,6 +329,47 @@ void iommu_device_unregister(struct iommu_device *iommu)
}
EXPORT_SYMBOL_GPL(iommu_device_unregister);
+struct iommu_dev_iter {
+ struct iommu_device *iommu;
+ iommu_dev_iter_fn fn;
+};
+
+static int _iommu_for_each_dev_cb(struct device *dev, void *data)
+{
+ struct iommu_dev_iter *iter = data;
+
+ if (dev->iommu && dev->iommu->iommu_dev == iter->iommu)
+ return iter->fn(dev, iter->iommu);
+
+ return 0;
+}
+
+/**
+ * iommu_for_each_dev() - Iterate over all devices attached to an IOMMU
+ * @iommu: IOMMU instance
+ * @fn: Callback to call for each device attached to @iommu
+ *
+ * Return: 0 on success, or negative error code.
+ */
+int iommu_for_each_dev(struct iommu_device *iommu, iommu_dev_iter_fn fn)
+{
+ struct iommu_dev_iter iter = {
+ .iommu = iommu,
+ .fn = fn,
+ };
+ int ret;
+
+ for (int i = 0; i < ARRAY_SIZE(iommu_buses); i++) {
+ ret = bus_for_each_dev(iommu_buses[i], NULL, &iter,
+ _iommu_for_each_dev_cb);
+ if (ret)
+ return ret;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(iommu_for_each_dev);
The function has no locking against iommu probe or release, so the
callback can read dev->iommu while it is being freed or before it is
fully set up.
It is only called from intel_iommu_shutdown(), which runs after the
other CPUs are stopped and interrupts are disabled, so probe and release
can't run. I will rename it to iommu_for_each_dev_unsafe(), document
that it must only be called at shutdown and drop the export, since the
only user is built in.
If it's only intended for the intel iommu driver, then it should be
open-coded there. There is no need to add an immature interface like
this to the core. It could be misused in the future.
Thanks,
baolu