From: Jacob Pan <jacob.pan@linux.microsoft.com>
To: linux-kernel@vger.kernel.org,
"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
Jason Gunthorpe <jgg@nvidia.com>,
Alex Williamson <alex@shazbot.org>,
Joerg Roedel <joro@8bytes.org>,
Mostafa Saleh <smostafa@google.com>,
David Matlack <dmatlack@google.com>,
Robin Murphy <robin.murphy@arm.com>,
Nicolin Chen <nicolinc@nvidia.com>,
"Tian, Kevin" <kevin.tian@intel.com>, Yi Liu <yi.l.liu@intel.com>,
Baolu Lu <baolu.lu@linux.intel.com>
Cc: Saurabh Sengar <ssengar@linux.microsoft.com>,
skhawaja@google.com, pasha.tatashin@soleen.com,
Will Deacon <will@kernel.org>,
Jacob Pan <jacob.pan@linux.microsoft.com>
Subject: [PATCH v8 1/6] iommufd: Support a HWPT without an iommu driver for noiommu
Date: Wed, 3 Jun 2026 15:02:06 -0700 [thread overview]
Message-ID: <20260603220211.2584590-2-jacob.pan@linux.microsoft.com> (raw)
In-Reply-To: <20260603220211.2584590-1-jacob.pan@linux.microsoft.com>
From: Jason Gunthorpe <jgg@nvidia.com>
Create just a little part of a real iommu driver, enough to
slot in under the dev_iommu_ops() and allow iommufd to call
domain_alloc_paging_flags() and fail everything else.
This allows explicitly creating a HWPT under an IOAS.
A new Kconfig option IOMMUFD_NOIOMMU is introduced to differentiate
from the VFIO group/container based noiommu mode.
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Jacob Pan <jacob.pan@linux.microsoft.com>
---
V8:
- Guard vIOMMU and vDevice allocation paths for noiommu (Sashiko)
v7:
- Drain no-IOMMU generic-PT freelist (Sashiko)
- Import generic-PT IOMMU namespace (Sashiko)
v6: (Yi)
- Sort includes alphabetically (iommu.h after generic_pt/iommu.h)
- Fix comment: s/mock page table/SW-only page table/ to avoid confusion
with selftest mock
- Rewrite noiommu_amdv1_ops comment: explain why AMDV1 format is chosen
(multi-page size options), remove references to group-container mode distinction
v5:
- Use the new IOMMUFD_NOIOMMU Kconfig instead of VFIO_NOIOMMU
- Use consistent wording referring to VFIO noiommu mode (Kevin)
- Copyright date fix (Kevin)
v4:
- Make iommufd_noiommu_ops const
v3:
- Add comment to explain the design difference over the
legacy noiommu VFIO code.
---
drivers/iommu/iommufd/Kconfig | 12 +++
drivers/iommu/iommufd/Makefile | 1 +
drivers/iommu/iommufd/hw_pagetable.c | 19 ++++-
drivers/iommu/iommufd/hwpt_noiommu.c | 105 ++++++++++++++++++++++++
drivers/iommu/iommufd/iommufd_private.h | 12 +++
drivers/iommu/iommufd/main.c | 1 +
drivers/iommu/iommufd/viommu.c | 14 +++-
7 files changed, 158 insertions(+), 6 deletions(-)
create mode 100644 drivers/iommu/iommufd/hwpt_noiommu.c
diff --git a/drivers/iommu/iommufd/Kconfig b/drivers/iommu/iommufd/Kconfig
index 455bac0351f2..6c3bea83631b 100644
--- a/drivers/iommu/iommufd/Kconfig
+++ b/drivers/iommu/iommufd/Kconfig
@@ -16,6 +16,18 @@ config IOMMUFD
If you don't know what to do here, say N.
if IOMMUFD
+config IOMMUFD_NOIOMMU
+ bool
+ depends on !GENERIC_ATOMIC64 # IOMMU_PT_AMDV1 requires cmpxchg64
+ select GENERIC_PT
+ select IOMMU_PT
+ select IOMMU_PT_AMDV1
+ help
+ Provides a SW-only IO page table for devices without hardware
+ IOMMU backing. This uses the AMDV1 page table format for
+ IOVA-to-PA lookups only, not for hardware DMA translation.
+ To be selected by VFIO_NOIOMMU when VFIO_DEVICE_CDEV is enabled.
+
config IOMMUFD_VFIO_CONTAINER
bool "IOMMUFD provides the VFIO container /dev/vfio/vfio"
depends on VFIO_GROUP && !VFIO_CONTAINER
diff --git a/drivers/iommu/iommufd/Makefile b/drivers/iommu/iommufd/Makefile
index 71d692c9a8f4..67207914bb6e 100644
--- a/drivers/iommu/iommufd/Makefile
+++ b/drivers/iommu/iommufd/Makefile
@@ -10,6 +10,7 @@ iommufd-y := \
vfio_compat.o \
viommu.o
+iommufd-$(CONFIG_IOMMUFD_NOIOMMU) += hwpt_noiommu.o
iommufd-$(CONFIG_IOMMUFD_TEST) += selftest.o
obj-$(CONFIG_IOMMUFD) += iommufd.o
diff --git a/drivers/iommu/iommufd/hw_pagetable.c b/drivers/iommu/iommufd/hw_pagetable.c
index fe789c2dc0c9..8f95c75d47f3 100644
--- a/drivers/iommu/iommufd/hw_pagetable.c
+++ b/drivers/iommu/iommufd/hw_pagetable.c
@@ -8,6 +8,15 @@
#include "../iommu-priv.h"
#include "iommufd_private.h"
+static const struct iommu_ops *get_iommu_ops(struct iommufd_device *idev)
+{
+ if (IS_ENABLED(CONFIG_IOMMUFD_NOIOMMU) && !idev->igroup->group)
+ return &iommufd_noiommu_ops;
+ if (WARN_ON_ONCE(!idev->dev->iommu))
+ return NULL;
+ return dev_iommu_ops(idev->dev);
+}
+
static void __iommufd_hwpt_destroy(struct iommufd_hw_pagetable *hwpt)
{
if (hwpt->domain)
@@ -114,11 +123,13 @@ iommufd_hwpt_paging_alloc(struct iommufd_ctx *ictx, struct iommufd_ioas *ioas,
IOMMU_HWPT_ALLOC_DIRTY_TRACKING |
IOMMU_HWPT_FAULT_ID_VALID |
IOMMU_HWPT_ALLOC_PASID;
- const struct iommu_ops *ops = dev_iommu_ops(idev->dev);
+ const struct iommu_ops *ops = get_iommu_ops(idev);
struct iommufd_hwpt_paging *hwpt_paging;
struct iommufd_hw_pagetable *hwpt;
int rc;
+ if (!ops)
+ return ERR_PTR(-ENODEV);
lockdep_assert_held(&ioas->mutex);
if ((flags || user_data) && !ops->domain_alloc_paging_flags)
@@ -229,7 +240,7 @@ iommufd_hwpt_nested_alloc(struct iommufd_ctx *ictx,
struct iommufd_device *idev, u32 flags,
const struct iommu_user_data *user_data)
{
- const struct iommu_ops *ops = dev_iommu_ops(idev->dev);
+ const struct iommu_ops *ops = get_iommu_ops(idev);
struct iommufd_hwpt_nested *hwpt_nested;
struct iommufd_hw_pagetable *hwpt;
int rc;
@@ -389,10 +400,12 @@ int iommufd_hwpt_alloc(struct iommufd_ucmd *ucmd)
hwpt = &hwpt_nested->common;
} else if (pt_obj->type == IOMMUFD_OBJ_VIOMMU) {
struct iommufd_hwpt_nested *hwpt_nested;
+ struct iommu_device *iommu_dev;
struct iommufd_viommu *viommu;
viommu = container_of(pt_obj, struct iommufd_viommu, obj);
- if (viommu->iommu_dev != __iommu_get_iommu_dev(idev->dev)) {
+ iommu_dev = iommufd_device_get_iommu_dev(idev);
+ if (!iommu_dev || viommu->iommu_dev != iommu_dev) {
rc = -EINVAL;
goto out_unlock;
}
diff --git a/drivers/iommu/iommufd/hwpt_noiommu.c b/drivers/iommu/iommufd/hwpt_noiommu.c
new file mode 100644
index 000000000000..9b8b5eb71491
--- /dev/null
+++ b/drivers/iommu/iommufd/hwpt_noiommu.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2026, NVIDIA CORPORATION & AFFILIATES
+ */
+#include <linux/generic_pt/iommu.h>
+#include <linux/iommu.h>
+#include "../iommu-pages.h"
+#include "iommufd_private.h"
+
+static const struct iommu_domain_ops noiommu_amdv1_ops;
+
+struct noiommu_domain {
+ union {
+ struct iommu_domain domain;
+ struct pt_iommu_amdv1 amdv1;
+ };
+ spinlock_t lock;
+};
+PT_IOMMU_CHECK_DOMAIN(struct noiommu_domain, amdv1.iommu, domain);
+
+static void noiommu_change_top(struct pt_iommu *iommu_table,
+ phys_addr_t top_paddr, unsigned int top_level)
+{
+}
+
+static spinlock_t *noiommu_get_top_lock(struct pt_iommu *iommupt)
+{
+ struct noiommu_domain *domain =
+ container_of(iommupt, struct noiommu_domain, amdv1.iommu);
+
+ return &domain->lock;
+}
+
+static const struct pt_iommu_driver_ops noiommu_driver_ops = {
+ .get_top_lock = noiommu_get_top_lock,
+ .change_top = noiommu_change_top,
+};
+
+static struct iommu_domain *
+noiommu_alloc_paging_flags(struct device *dev, u32 flags,
+ const struct iommu_user_data *user_data)
+{
+ struct pt_iommu_amdv1_cfg cfg = {};
+ struct noiommu_domain *dom;
+ int rc;
+
+ if (flags || user_data)
+ return ERR_PTR(-EOPNOTSUPP);
+
+ cfg.common.hw_max_vasz_lg2 = 64;
+ cfg.common.hw_max_oasz_lg2 = 52;
+ cfg.starting_level = 2;
+ cfg.common.features =
+ (BIT(PT_FEAT_DYNAMIC_TOP) | BIT(PT_FEAT_AMDV1_ENCRYPT_TABLES) |
+ BIT(PT_FEAT_AMDV1_FORCE_COHERENCE));
+
+ dom = kzalloc(sizeof(*dom), GFP_KERNEL);
+ if (!dom)
+ return ERR_PTR(-ENOMEM);
+
+ spin_lock_init(&dom->lock);
+ dom->amdv1.iommu.nid = NUMA_NO_NODE;
+ dom->amdv1.iommu.driver_ops = &noiommu_driver_ops;
+ dom->domain.ops = &noiommu_amdv1_ops;
+
+ /* Use SW-only page table which is based on AMDV1 */
+ rc = pt_iommu_amdv1_init(&dom->amdv1, &cfg, GFP_KERNEL);
+ if (rc) {
+ kfree(dom);
+ return ERR_PTR(rc);
+ }
+
+ return &dom->domain;
+}
+
+static void noiommu_domain_free(struct iommu_domain *iommu_domain)
+{
+ struct noiommu_domain *domain =
+ container_of(iommu_domain, struct noiommu_domain, domain);
+
+ pt_iommu_deinit(&domain->amdv1.iommu);
+ kfree(domain);
+}
+
+static void noiommu_iotlb_sync(struct iommu_domain *domain,
+ struct iommu_iotlb_gather *gather)
+{
+ iommu_put_pages_list(&gather->freelist);
+}
+
+/*
+ * Domain ops for iommufd no-IOMMU mode. Uses AMDV1 format as a
+ * SW-only IOPT because it has the best multi-page size options
+ * of all the formats. IOVAs serve only for IOVA-to-PA lookups,
+ * not for hardware DMA translation.
+ */
+static const struct iommu_domain_ops noiommu_amdv1_ops = {
+ IOMMU_PT_DOMAIN_OPS(amdv1),
+ .iotlb_sync = noiommu_iotlb_sync,
+ .free = noiommu_domain_free,
+};
+
+const struct iommu_ops iommufd_noiommu_ops = {
+ .domain_alloc_paging_flags = noiommu_alloc_paging_flags,
+};
diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index 6ac1965199e9..c8ed612e896a 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -464,6 +464,8 @@ static inline void iommufd_hw_pagetable_put(struct iommufd_ctx *ictx,
refcount_dec(&hwpt->obj.users);
}
+extern const struct iommu_ops iommufd_noiommu_ops;
+
struct iommufd_attach;
struct iommufd_group {
@@ -501,6 +503,16 @@ iommufd_get_device(struct iommufd_ucmd *ucmd, u32 id)
struct iommufd_device, obj);
}
+static inline struct iommu_device *
+iommufd_device_get_iommu_dev(struct iommufd_device *idev)
+{
+ if (IS_ENABLED(CONFIG_IOMMUFD_NOIOMMU) && !idev->igroup->group)
+ return NULL;
+ if (WARN_ON_ONCE(!idev->dev->iommu))
+ return NULL;
+ return __iommu_get_iommu_dev(idev->dev);
+}
+
void iommufd_device_pre_destroy(struct iommufd_object *obj);
void iommufd_device_destroy(struct iommufd_object *obj);
int iommufd_get_hw_info(struct iommufd_ucmd *ucmd);
diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
index 8c6d43601afb..f6ae60bd3f70 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -804,5 +804,6 @@ MODULE_ALIAS("devname:vfio/vfio");
MODULE_IMPORT_NS("IOMMUFD_INTERNAL");
MODULE_IMPORT_NS("IOMMUFD");
MODULE_IMPORT_NS("DMA_BUF");
+MODULE_IMPORT_NS("GENERIC_PT_IOMMU");
MODULE_DESCRIPTION("I/O Address Space Management for passthrough devices");
MODULE_LICENSE("GPL");
diff --git a/drivers/iommu/iommufd/viommu.c b/drivers/iommu/iommufd/viommu.c
index 4081deda9b33..b51f67fdf4e3 100644
--- a/drivers/iommu/iommufd/viommu.c
+++ b/drivers/iommu/iommufd/viommu.c
@@ -25,6 +25,7 @@ int iommufd_viommu_alloc_ioctl(struct iommufd_ucmd *ucmd)
struct iommufd_hwpt_paging *hwpt_paging;
struct iommufd_viommu *viommu;
struct iommufd_device *idev;
+ struct iommu_device *iommu_dev;
const struct iommu_ops *ops;
size_t viommu_size;
int rc;
@@ -36,7 +37,12 @@ int iommufd_viommu_alloc_ioctl(struct iommufd_ucmd *ucmd)
if (IS_ERR(idev))
return PTR_ERR(idev);
- ops = dev_iommu_ops(idev->dev);
+ iommu_dev = iommufd_device_get_iommu_dev(idev);
+ if (!iommu_dev) {
+ rc = -EOPNOTSUPP;
+ goto out_put_idev;
+ }
+ ops = iommu_dev->ops;
if (!ops->get_viommu_size || !ops->viommu_init) {
rc = -EOPNOTSUPP;
goto out_put_idev;
@@ -87,7 +93,7 @@ int iommufd_viommu_alloc_ioctl(struct iommufd_ucmd *ucmd)
* pluggable IOMMU instance (if exists) is responsible for refcounting
* on its own.
*/
- viommu->iommu_dev = __iommu_get_iommu_dev(idev->dev);
+ viommu->iommu_dev = iommu_dev;
rc = ops->viommu_init(viommu, hwpt_paging->common.domain,
user_data.len ? &user_data : NULL);
@@ -146,6 +152,7 @@ int iommufd_vdevice_alloc_ioctl(struct iommufd_ucmd *ucmd)
struct iommufd_vdevice *vdev, *curr;
size_t vdev_size = sizeof(*vdev);
struct iommufd_viommu *viommu;
+ struct iommu_device *iommu_dev;
struct iommufd_device *idev;
u64 virt_id = cmd->virt_id;
int rc = 0;
@@ -164,7 +171,8 @@ int iommufd_vdevice_alloc_ioctl(struct iommufd_ucmd *ucmd)
goto out_put_viommu;
}
- if (viommu->iommu_dev != __iommu_get_iommu_dev(idev->dev)) {
+ iommu_dev = iommufd_device_get_iommu_dev(idev);
+ if (!iommu_dev || viommu->iommu_dev != iommu_dev) {
rc = -EINVAL;
goto out_put_idev;
}
--
2.43.0
next prev parent reply other threads:[~2026-06-03 22:02 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-03 22:02 [PATCH v8 0/6] iommufd: Enable noiommu mode for cdev Jacob Pan
2026-06-03 22:02 ` Jacob Pan [this message]
2026-06-03 22:02 ` [PATCH v8 2/6] iommufd: Move igroup allocation to a function Jacob Pan
2026-06-03 22:02 ` [PATCH v8 3/6] iommufd: Allow binding to a noiommu device Jacob Pan
2026-06-03 22:02 ` [PATCH v8 4/6] iommufd: Add an ioctl to query PA from IOVA for noiommu mode Jacob Pan
2026-06-03 22:02 ` [PATCH v8 5/6] vfio: Enable cdev noiommu mode under iommufd Jacob Pan
2026-06-08 23:19 ` Alex Williamson
2026-06-09 18:50 ` Jacob Pan
2026-06-09 20:07 ` Alex Williamson
2026-06-09 21:11 ` Jacob Pan
2026-06-03 22:02 ` [PATCH v8 6/6] Documentation: Update VFIO NOIOMMU mode Jacob Pan
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