[PATCH v4 08/21] iommu/riscv: Add IRQ domain for interrupt remapping
From: Andrew Jones
Date: Thu Aug 20 2026 - 17:43:01 EST
Create a per-device MSI parent domain as a hook for interrupt remapping.
Keep the remapping tables with the attached paging domain because MSI
IOVA mappings are part of its page tables.
Initially, the new domain only forwards operations to its parent. Later
commits add MSI target mappings for paging domains, while non-paging
domains continue to use physical IMSIC addresses.
Signed-off-by: Andrew Jones <andrew.jones@xxxxxxxxxxxxxxxx>
---
drivers/iommu/riscv/Makefile | 2 +-
drivers/iommu/riscv/iommu-ir.c | 118 ++++++++++++++++++++++++++++
drivers/iommu/riscv/iommu.c | 46 ++++++-----
drivers/iommu/riscv/iommu.h | 27 +++++++
include/linux/irqchip/riscv-imsic.h | 7 ++
5 files changed, 181 insertions(+), 19 deletions(-)
create mode 100644 drivers/iommu/riscv/iommu-ir.c
diff --git a/drivers/iommu/riscv/Makefile b/drivers/iommu/riscv/Makefile
index b5929f9f23e6..9c83f877d50f 100644
--- a/drivers/iommu/riscv/Makefile
+++ b/drivers/iommu/riscv/Makefile
@@ -1,3 +1,3 @@
# SPDX-License-Identifier: GPL-2.0-only
-obj-y += iommu.o iommu-platform.o
+obj-y += iommu.o iommu-ir.o iommu-platform.o
obj-$(CONFIG_RISCV_IOMMU_PCI) += iommu-pci.o
diff --git a/drivers/iommu/riscv/iommu-ir.c b/drivers/iommu/riscv/iommu-ir.c
new file mode 100644
index 000000000000..0aab0efeb70e
--- /dev/null
+++ b/drivers/iommu/riscv/iommu-ir.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * IOMMU Interrupt Remapping
+ *
+ * Copyright (c) 2026 Qualcomm Technologies, Inc.
+ */
+#include <linux/cleanup.h>
+#include <linux/msi.h>
+#include <linux/slab.h>
+
+#include "iommu.h"
+
+static struct irq_chip riscv_iommu_ir_irq_chip = {
+ .name = "IOMMU-IR",
+ .irq_ack = irq_chip_ack_parent,
+ .irq_mask = irq_chip_mask_parent,
+ .irq_unmask = irq_chip_unmask_parent,
+ .irq_set_affinity = irq_chip_set_affinity_parent,
+};
+
+static int riscv_iommu_ir_irq_domain_alloc_irqs(struct irq_domain *irqdomain,
+ unsigned int irq_base, unsigned int nr_irqs,
+ void *arg)
+{
+ int ret;
+
+ ret = irq_domain_alloc_irqs_parent(irqdomain, irq_base, nr_irqs, arg);
+ if (ret)
+ return ret;
+
+ for (unsigned int i = 0; i < nr_irqs; i++) {
+ struct irq_data *data = irq_domain_get_irq_data(irqdomain, irq_base + i);
+
+ data->chip = &riscv_iommu_ir_irq_chip;
+ }
+
+ return 0;
+}
+
+static const struct irq_domain_ops riscv_iommu_ir_irq_domain_ops = {
+ .alloc = riscv_iommu_ir_irq_domain_alloc_irqs,
+ .free = irq_domain_free_irqs_parent,
+};
+
+static const struct msi_parent_ops riscv_iommu_ir_msi_parent_ops = {
+ .prefix = "IR-",
+ .supported_flags = MSI_GENERIC_FLAGS_MASK |
+ MSI_FLAG_PCI_MSIX,
+ .required_flags = MSI_FLAG_USE_DEF_DOM_OPS |
+ MSI_FLAG_USE_DEF_CHIP_OPS |
+ MSI_FLAG_PCI_MSI_MASK_PARENT,
+ .chip_flags = MSI_CHIP_FLAG_SET_ACK,
+ .init_dev_msi_info = msi_parent_init_dev_msi_info,
+};
+
+struct irq_domain *riscv_iommu_ir_irq_domain_create(struct device *dev,
+ struct riscv_iommu_info *info)
+{
+ struct irq_domain *irqparent = dev_get_msi_domain(dev);
+ char *fwname __free(kfree) = NULL;
+ struct irq_domain *irqdomain;
+ struct fwnode_handle *fn;
+
+ if (!irqparent)
+ return NULL;
+
+ fwname = kasprintf(GFP_KERNEL, "IOMMU-IR-%s", dev_name(dev));
+ if (!fwname)
+ return ERR_PTR(-ENOMEM);
+
+ fn = irq_domain_alloc_named_fwnode(fwname);
+ if (!fn)
+ return ERR_PTR(-ENOMEM);
+
+ irqdomain = irq_domain_create_hierarchy(irqparent, 0, 0, fn,
+ &riscv_iommu_ir_irq_domain_ops, info);
+ if (!irqdomain) {
+ irq_domain_free_fwnode(fn);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ /*
+ * The RISC-V IOMMU doesn't validate MSI data, so we can't set
+ * IRQ_DOMAIN_FLAG_ISOLATED_MSI. This means VFIO requires its
+ * allow_unsafe_interrupts module parameter.
+ */
+ irqdomain->flags |= IRQ_DOMAIN_FLAG_MSI_PARENT;
+ irqdomain->msi_parent_ops = &riscv_iommu_ir_msi_parent_ops;
+ irq_domain_update_bus_token(irqdomain, DOMAIN_BUS_MSI_REMAP);
+
+ dev_set_msi_domain(dev, irqdomain);
+
+ return irqdomain;
+}
+
+void riscv_iommu_ir_irq_domain_remove(struct device *dev, struct riscv_iommu_info *info)
+{
+ struct fwnode_handle *fn;
+
+ if (!info->irqdomain)
+ return;
+
+ dev_set_msi_domain(dev, info->irqdomain->parent);
+ fn = info->irqdomain->fwnode;
+ irq_domain_remove(info->irqdomain);
+ info->irqdomain = NULL;
+ irq_domain_free_fwnode(fn);
+}
+
+int riscv_iommu_ir_attach_paging_domain(struct iommu_domain *iommu_domain, struct device *dev,
+ struct iommu_domain *old)
+{
+ return 0;
+}
+
+void riscv_iommu_ir_free_paging_domain(struct iommu_domain *iommu_domain)
+{
+}
diff --git a/drivers/iommu/riscv/iommu.c b/drivers/iommu/riscv/iommu.c
index cec3ddd7ab10..bfe606a0cb9a 100644
--- a/drivers/iommu/riscv/iommu.c
+++ b/drivers/iommu/riscv/iommu.c
@@ -19,9 +19,9 @@
#include <linux/init.h>
#include <linux/iommu.h>
#include <linux/iopoll.h>
+#include <linux/irqchip/riscv-imsic.h>
#include <linux/kernel.h>
#include <linux/pci.h>
-#include <linux/generic_pt/iommu.h>
#include "../iommu-pages.h"
#include "iommu-bits.h"
@@ -810,26 +810,9 @@ static int riscv_iommu_iodir_set_mode(struct riscv_iommu_device *iommu,
return 0;
}
-/* This struct contains protection domain specific IOMMU driver data. */
-struct riscv_iommu_domain {
- union {
- struct iommu_domain domain;
- struct pt_iommu_riscv_64 riscvpt;
- };
- struct list_head bonds;
- spinlock_t lock; /* protect bonds list updates. */
- int pscid;
-};
-PT_IOMMU_CHECK_DOMAIN(struct riscv_iommu_domain, riscvpt.iommu, domain);
-
#define iommu_domain_to_riscv(iommu_domain) \
container_of(iommu_domain, struct riscv_iommu_domain, domain)
-/* Private IOMMU data for managed devices, dev_iommu_priv_* */
-struct riscv_iommu_info {
- struct riscv_iommu_domain *domain;
-};
-
/*
* Linkage between an iommu_domain and attached devices.
*
@@ -1258,6 +1241,8 @@ static void riscv_iommu_free_paging_domain(struct iommu_domain *iommu_domain)
WARN_ON(!list_empty(&domain->bonds));
+ riscv_iommu_ir_free_paging_domain(iommu_domain);
+
if ((int)domain->pscid > 0)
ida_free(&riscv_iommu_pscids, domain->pscid);
@@ -1289,6 +1274,7 @@ static int riscv_iommu_attach_paging_domain(struct iommu_domain *iommu_domain,
struct riscv_iommu_info *info = dev_iommu_priv_get(dev);
struct pt_iommu_riscv_64_hw_info pt_info;
u64 fsc, ta;
+ int ret;
pt_iommu_riscv_64_hw_info(&domain->riscvpt, &pt_info);
@@ -1303,6 +1289,12 @@ static int riscv_iommu_attach_paging_domain(struct iommu_domain *iommu_domain,
if (riscv_iommu_bond_link(domain, dev))
return -ENOMEM;
+ ret = riscv_iommu_ir_attach_paging_domain(iommu_domain, dev, old);
+ if (ret) {
+ riscv_iommu_bond_unlink(domain, dev);
+ return ret;
+ }
+
riscv_iommu_iodir_update(iommu, dev, fsc, ta);
riscv_iommu_bond_unlink(info->domain, dev);
info->domain = domain;
@@ -1430,6 +1422,7 @@ static int riscv_iommu_of_xlate(struct device *dev, const struct of_phandle_args
static struct iommu_device *riscv_iommu_probe_device(struct device *dev)
{
struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
+ struct irq_domain *irqdomain = NULL;
struct riscv_iommu_device *iommu;
struct riscv_iommu_info *info;
struct riscv_iommu_dc *dc;
@@ -1453,6 +1446,21 @@ static struct iommu_device *riscv_iommu_probe_device(struct device *dev)
info = kzalloc_obj(*info);
if (!info)
return ERR_PTR(-ENOMEM);
+
+ if (imsic_enabled()) {
+ irqdomain = riscv_iommu_ir_irq_domain_create(dev, info);
+ if (IS_ERR(irqdomain)) {
+ kfree(info);
+ return ERR_CAST(irqdomain);
+ }
+ }
+
+ /*
+ * irqdomain is NULL when it's not necessary; either there aren't
+ * any IMSICs or no MSI domain has been set up for the device.
+ */
+ info->irqdomain = irqdomain;
+
/*
* Allocate and pre-configure device context entries in
* the device directory. Do not mark the context valid yet.
@@ -1461,6 +1469,7 @@ static struct iommu_device *riscv_iommu_probe_device(struct device *dev)
for (i = 0; i < fwspec->num_ids; i++) {
dc = riscv_iommu_get_dc(iommu, fwspec->ids[i]);
if (!dc) {
+ riscv_iommu_ir_irq_domain_remove(dev, info);
kfree(info);
return ERR_PTR(-ENODEV);
}
@@ -1478,6 +1487,7 @@ static void riscv_iommu_release_device(struct device *dev)
{
struct riscv_iommu_info *info = dev_iommu_priv_get(dev);
+ riscv_iommu_ir_irq_domain_remove(dev, info);
kfree_rcu_mightsleep(info);
}
diff --git a/drivers/iommu/riscv/iommu.h b/drivers/iommu/riscv/iommu.h
index 46df79dd5495..5d83537911b6 100644
--- a/drivers/iommu/riscv/iommu.h
+++ b/drivers/iommu/riscv/iommu.h
@@ -14,9 +14,29 @@
#include <linux/iommu.h>
#include <linux/types.h>
#include <linux/iopoll.h>
+#include <linux/irqdomain.h>
+#include <linux/generic_pt/iommu.h>
#include "iommu-bits.h"
+/* This struct contains protection domain specific IOMMU driver data. */
+struct riscv_iommu_domain {
+ union {
+ struct iommu_domain domain;
+ struct pt_iommu_riscv_64 riscvpt;
+ };
+ struct list_head bonds;
+ spinlock_t lock; /* protect bonds list updates. */
+ int pscid;
+};
+PT_IOMMU_CHECK_DOMAIN(struct riscv_iommu_domain, riscvpt.iommu, domain);
+
+/* Private IOMMU data for managed devices, dev_iommu_priv_* */
+struct riscv_iommu_info {
+ struct riscv_iommu_domain *domain;
+ struct irq_domain *irqdomain;
+};
+
struct riscv_iommu_device;
struct riscv_iommu_queue {
@@ -66,6 +86,13 @@ int riscv_iommu_init(struct riscv_iommu_device *iommu);
void riscv_iommu_remove(struct riscv_iommu_device *iommu);
void riscv_iommu_disable(struct riscv_iommu_device *iommu);
+struct irq_domain *riscv_iommu_ir_irq_domain_create(struct device *dev,
+ struct riscv_iommu_info *info);
+void riscv_iommu_ir_irq_domain_remove(struct device *dev, struct riscv_iommu_info *info);
+int riscv_iommu_ir_attach_paging_domain(struct iommu_domain *iommu_domain, struct device *dev,
+ struct iommu_domain *old);
+void riscv_iommu_ir_free_paging_domain(struct iommu_domain *iommu_domain);
+
#define riscv_iommu_readl(iommu, addr) \
readl_relaxed((iommu)->reg + (addr))
diff --git a/include/linux/irqchip/riscv-imsic.h b/include/linux/irqchip/riscv-imsic.h
index 61af3a5bea09..ce8fe1ead7a0 100644
--- a/include/linux/irqchip/riscv-imsic.h
+++ b/include/linux/irqchip/riscv-imsic.h
@@ -91,6 +91,13 @@ static inline const struct imsic_global_config *imsic_get_global_config(void)
#endif
+static inline bool imsic_enabled(void)
+{
+ const struct imsic_global_config *imsic_global = imsic_get_global_config();
+
+ return imsic_global && imsic_global->nr_ids;
+}
+
#if IS_ENABLED(CONFIG_ACPI) && IS_ENABLED(CONFIG_RISCV_IMSIC)
int imsic_platform_acpi_probe(struct fwnode_handle *fwnode);
struct fwnode_handle *imsic_acpi_get_fwnode(struct device *dev);
--
2.43.0