[PATCH V0 0/3] Hyper-V: root VM iommu kernel only driver

[PATCH V0 0/3] Hyper-V: root VM iommu kernel only driver

[Mukesh R]

This short series introduces hyperv root VM iommu kernel only driver. This
driver acts as liason between the hypervisor and iommu layer. Details are
both in the actual commit and in the comments in the file implementing it.

Thanks,
-Mukesh

V0: based on upstream hyperv-next commit be0cfab740e5

Mukesh R (3):
  PCI: hv: Export hv_build_devid_type_pci() and change return type
  mshv: Import data structs around device domains from hyperv headers
  x86/hyperv: Implement Hyper-V virtual IOMMU on root VMs

 arch/x86/hyperv/irqdomain.c          |   9 +-
 arch/x86/include/asm/mshyperv.h      |   6 +
 arch/x86/kernel/pci-dma.c            |   2 +
 drivers/iommu/Kconfig                |   1 +
 drivers/iommu/hyperv/Kconfig         |  15 +
 drivers/iommu/hyperv/Makefile        |   1 +
 drivers/iommu/hyperv/hv-iommu-root.c | 645 +++++++++++++++++++++++++++
 include/asm-generic/mshyperv.h       |   3 +
 include/hyperv/hvgdk_mini.h          |   9 +
 include/hyperv/hvhdk_mini.h          |  90 ++++
 include/linux/hyperv.h               |   6 +
 11 files changed, 783 insertions(+), 4 deletions(-)
 create mode 100644 drivers/iommu/hyperv/Kconfig
 create mode 100644 drivers/iommu/hyperv/hv-iommu-root.c

-- 
2.51.2.vfs.0.1

[PATCH V0 1/3] PCI: hv: Export hv_build_devid_type_pci() and change return type

[Mukesh R]

On Hyper-V, most hypercalls related to device domain management like
attach device to a device domain, or to map/unmap regions, interrupts,
etc need a device ID as a parameter. So, make hv_build_devid_type_pci()
public and change return type to u64 to enforce it's size.

Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
Reviewed-by: Souradeep Chakrabarti <schakrabarti@linux.microsoft.com>
---
 arch/x86/hyperv/irqdomain.c     | 9 +++++----
 arch/x86/include/asm/mshyperv.h | 6 ++++++
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/arch/x86/hyperv/irqdomain.c b/arch/x86/hyperv/irqdomain.c
index b3ad50a874dc..8780573a4332 100644
--- a/arch/x86/hyperv/irqdomain.c
+++ b/arch/x86/hyperv/irqdomain.c
@@ -112,7 +112,7 @@ static int get_rid_cb(struct pci_dev *pdev, u16 alias, void *data)
 	return 0;
 }
 
-static union hv_device_id hv_build_devid_type_pci(struct pci_dev *pdev)
+u64 hv_build_devid_type_pci(struct pci_dev *pdev)
 {
 	int pos;
 	union hv_device_id hv_devid;
@@ -172,8 +172,9 @@ static union hv_device_id hv_build_devid_type_pci(struct pci_dev *pdev)
 	}
 
 out:
-	return hv_devid;
+	return hv_devid.as_uint64;
 }
+EXPORT_SYMBOL_GPL(hv_build_devid_type_pci);
 
 /*
  * hv_map_msi_interrupt() - Map the MSI IRQ in the hypervisor.
@@ -196,7 +197,7 @@ int hv_map_msi_interrupt(struct irq_data *data,
 
 	msidesc = irq_data_get_msi_desc(data);
 	pdev = msi_desc_to_pci_dev(msidesc);
-	hv_devid = hv_build_devid_type_pci(pdev);
+	hv_devid.as_uint64 = hv_build_devid_type_pci(pdev);
 	cpu = cpumask_first(irq_data_get_effective_affinity_mask(data));
 
 	return hv_map_interrupt(hv_devid, false, cpu, cfg->vector,
@@ -271,7 +272,7 @@ static int hv_unmap_msi_interrupt(struct pci_dev *pdev,
 {
 	union hv_device_id hv_devid;
 
-	hv_devid = hv_build_devid_type_pci(pdev);
+	hv_devid.as_uint64 = hv_build_devid_type_pci(pdev);
 	return hv_unmap_interrupt(hv_devid.as_uint64, irq_entry);
 }
 
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index f64393e853ee..8ebbd1cb7c8c 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -248,6 +248,12 @@ void hv_crash_asm_end(void);
 static inline void hv_root_crash_init(void) {}
 #endif  /* CONFIG_MSHV_ROOT && CONFIG_CRASH_DUMP */
 
+#ifdef CONFIG_PCI_MSI
+u64 hv_build_devid_type_pci(struct pci_dev *pdev);
+#else
+static inline u64 hv_build_devid_type_pci(struct pci_dev *pdev) { return 0; }
+#endif
+
 #else /* CONFIG_HYPERV */
 static inline void hyperv_init(void) {}
 static inline void hyperv_setup_mmu_ops(void) {}
-- 
2.51.2.vfs.0.1

[PATCH V0 2/3] mshv: Import data structs around device domains from hyperv headers

[Mukesh R]

Copy/import from Hyper-V public headers, definitions and declarations that
are related to creating iommu domains in the hypervisor, attaching devices
to them, doing the reverse, etc.

Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
---
 include/hyperv/hvgdk_mini.h |  9 ++++
 include/hyperv/hvhdk_mini.h | 90 +++++++++++++++++++++++++++++++++++++
 2 files changed, 99 insertions(+)

diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h
index 6a4e8b9d570f..3b74f3c0229d 100644
--- a/include/hyperv/hvgdk_mini.h
+++ b/include/hyperv/hvgdk_mini.h
@@ -326,6 +326,8 @@ union hv_hypervisor_version_info {
 /* stimer Direct Mode is available */
 #define HV_STIMER_DIRECT_MODE_AVAILABLE			BIT(19)
 
+#define HV_DEVICE_DOMAIN_AVAILABLE			BIT(24)
+
 /*
  * Implementation recommendations. Indicates which behaviors the hypervisor
  * recommends the OS implement for optimal performance.
@@ -486,9 +488,15 @@ union hv_vp_assist_msr_contents {	 /* HV_REGISTER_VP_ASSIST_PAGE */
 #define HVCALL_GET_VP_INDEX_FROM_APIC_ID		0x009a
 #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE	0x00af
 #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_LIST	0x00b0
+#define HVCALL_CREATE_DEVICE_DOMAIN                     0x00b1
+#define HVCALL_ATTACH_DEVICE_DOMAIN                     0x00b2
+#define HVCALL_MAP_DEVICE_GPA_PAGES                     0x00b3
+#define HVCALL_UNMAP_DEVICE_GPA_PAGES                   0x00b4
 #define HVCALL_SIGNAL_EVENT_DIRECT			0x00c0
 #define HVCALL_POST_MESSAGE_DIRECT			0x00c1
 #define HVCALL_DISPATCH_VP				0x00c2
+#define HVCALL_DETACH_DEVICE_DOMAIN                     0x00c4
+#define HVCALL_DELETE_DEVICE_DOMAIN                     0x00c5
 #define HVCALL_GET_GPA_PAGES_ACCESS_STATES		0x00c9
 #define HVCALL_ACQUIRE_SPARSE_SPA_PAGE_HOST_ACCESS	0x00d7
 #define HVCALL_RELEASE_SPARSE_SPA_PAGE_HOST_ACCESS	0x00d8
@@ -502,6 +510,7 @@ union hv_vp_assist_msr_contents {	 /* HV_REGISTER_VP_ASSIST_PAGE */
 #define HVCALL_MMIO_READ				0x0106
 #define HVCALL_MMIO_WRITE				0x0107
 #define HVCALL_DISABLE_HYP_EX                           0x010f
+#define HVCALL_GET_IOMMU_CAPABILITIES			0x0125
 #define HVCALL_MAP_STATS_PAGE2				0x0131
 
 /* HV_HYPERCALL_INPUT */
diff --git a/include/hyperv/hvhdk_mini.h b/include/hyperv/hvhdk_mini.h
index 035ba20870f7..3bb052fd6e06 100644
--- a/include/hyperv/hvhdk_mini.h
+++ b/include/hyperv/hvhdk_mini.h
@@ -548,4 +548,94 @@ union hv_device_id {		/* HV_DEVICE_ID */
 	} acpi;
 } __packed;
 
+/* 3 domain types: stage 1, stage 2, and SOC */
+#define HV_DEVICE_DOMAIN_TYPE_S2  0 /* HV_DEVICE_DOMAIN_ID_TYPE_S2 */
+#define HV_DEVICE_DOMAIN_TYPE_S1  1 /* HV_DEVICE_DOMAIN_ID_TYPE_S1 */
+#define HV_DEVICE_DOMAIN_TYPE_SOC 2 /* HV_DEVICE_DOMAIN_ID_TYPE_SOC */
+
+/* ID for stage 2 default domain and NULL domain */
+#define HV_DEVICE_DOMAIN_ID_S2_DEFAULT 0
+#define HV_DEVICE_DOMAIN_ID_S2_NULL    0xFFFFFFFFULL
+
+union hv_device_domain_id {
+	u64 as_uint64;
+	struct {
+		u32 type : 4;
+		u32 reserved : 28;
+		u32 id;
+	};
+} __packed;
+
+struct hv_input_device_domain { /* HV_INPUT_DEVICE_DOMAIN */
+	u64 partition_id;
+	union hv_input_vtl owner_vtl;
+	u8 padding[7];
+	union hv_device_domain_id domain_id;
+} __packed;
+
+union hv_create_device_domain_flags {	/* HV_CREATE_DEVICE_DOMAIN_FLAGS */
+	u32 as_uint32;
+	struct {
+		u32 forward_progress_required : 1;
+		u32 inherit_owning_vtl : 1;
+		u32 reserved : 30;
+	} __packed;
+} __packed;
+
+struct hv_input_create_device_domain {	/* HV_INPUT_CREATE_DEVICE_DOMAIN */
+	struct hv_input_device_domain device_domain;
+	union hv_create_device_domain_flags create_device_domain_flags;
+} __packed;
+
+struct hv_input_delete_device_domain {	/* HV_INPUT_DELETE_DEVICE_DOMAIN */
+	struct hv_input_device_domain device_domain;
+} __packed;
+
+struct hv_input_attach_device_domain {	/* HV_INPUT_ATTACH_DEVICE_DOMAIN */
+	struct hv_input_device_domain device_domain;
+	union hv_device_id device_id;
+} __packed;
+
+struct hv_input_detach_device_domain {	/* HV_INPUT_DETACH_DEVICE_DOMAIN */
+	u64 partition_id;
+	union hv_device_id device_id;
+} __packed;
+
+/* HV_INPUT_GET_IOMMU_CAPABILITIES */
+struct hv_input_get_iommu_capabilities {
+	u64 partition_id;
+	u64 reserved;
+} __packed;
+
+#define HV_IOMMU_CAP_PRESENT    BIT_ULL(0)
+#define HV_IOMMU_CAP_S2         BIT_ULL(1)
+#define HV_IOMMU_CAP_S1         BIT_ULL(2)
+#define HV_IOMMU_CAP_S1_5LVL    BIT_ULL(3)
+#define HV_IOMMU_CAP_PASID      BIT_ULL(4)
+#define HV_IOMMU_CAP_ATS        BIT_ULL(5)
+#define HV_IOMMU_CAP_PRI        BIT_ULL(6)
+
+struct hv_output_get_iommu_capabilities { /* HV_OUTPUT_GET_IOMMU_CAPABILITIES */
+	u32 size;
+	u16 reserved;
+	u8  max_iova_width;
+	u8  max_pasid_width;
+	u64 iommu_cap;          /* HV_IOMMU_CAP_* above */
+	u64 pgsize_bitmap;
+} __packed;
+
+struct hv_input_map_device_gpa_pages {	/* HV_INPUT_MAP_DEVICE_GPA_PAGES */
+	struct hv_input_device_domain device_domain;
+	union hv_input_vtl target_vtl;
+	u8 padding[3];
+	u32 map_flags;
+	u64 target_device_va_base;
+	u64 gpa_page_list[];
+} __packed;
+
+struct hv_input_unmap_device_gpa_pages {  /* HV_INPUT_UNMAP_DEVICE_GPA_PAGES */
+	struct hv_input_device_domain device_domain;
+	u64 target_device_va_base;
+} __packed;
+
 #endif /* _HV_HVHDK_MINI_H */
-- 
2.51.2.vfs.0.1

[PATCH V0 3/3] x86/hyperv: Implement root VM IOMMU kernel only driver

[Mukesh R]

Add a new file to implement a kernel only virtual IOMMU that works
with Microsoft Hyper-V hypervisor on privileged VMs aka root VMs. The
hypervisor claims the IOMMU upon boot, and this driver communicates with
it for creating and deleting paging domains, attaching of devices, mapping
and unmapping of pages, etc. During boot, hypervisor automatically creates
identity and blocked domains, so there is no need to do hypercalls to
create them.  This is a kernel only driver and only supported on baremetal
root (and not L1VH root) without any guest passthru support. Support
for guest device passthru will be added incrementally.

Signed-off-by: Mukesh R <mrathor@linux.microsoft.com>
---
 arch/x86/kernel/pci-dma.c            |   2 +
 drivers/iommu/Kconfig                |   1 +
 drivers/iommu/hyperv/Kconfig         |  15 +
 drivers/iommu/hyperv/Makefile        |   1 +
 drivers/iommu/hyperv/hv-iommu-root.c | 645 +++++++++++++++++++++++++++
 include/asm-generic/mshyperv.h       |   3 +
 include/linux/hyperv.h               |   6 +
 7 files changed, 673 insertions(+)
 create mode 100644 drivers/iommu/hyperv/Kconfig
 create mode 100644 drivers/iommu/hyperv/hv-iommu-root.c

diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 6267363e0189..37fed8c7a8c2 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -8,6 +8,7 @@
 #include <linux/gfp.h>
 #include <linux/pci.h>
 #include <linux/amd-iommu.h>
+#include <linux/hyperv.h>
 
 #include <asm/proto.h>
 #include <asm/dma.h>
@@ -103,6 +104,7 @@ void __init pci_iommu_alloc(void)
 	}
 	pci_swiotlb_detect();
 	gart_iommu_hole_init();
+	hv_iommu_detect();
 	amd_iommu_detect();
 	detect_intel_iommu();
 	swiotlb_init(x86_swiotlb_enable, x86_swiotlb_flags);
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 6e07bd69467a..3e410e0f3e1d 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -197,6 +197,7 @@ source "drivers/iommu/arm/Kconfig"
 source "drivers/iommu/intel/Kconfig"
 source "drivers/iommu/iommufd/Kconfig"
 source "drivers/iommu/riscv/Kconfig"
+source "drivers/iommu/hyperv/Kconfig"
 
 config IRQ_REMAP
 	bool "Support for Interrupt Remapping"
diff --git a/drivers/iommu/hyperv/Kconfig b/drivers/iommu/hyperv/Kconfig
new file mode 100644
index 000000000000..4342043443e7
--- /dev/null
+++ b/drivers/iommu/hyperv/Kconfig
@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# Hyper-V IOMMU support
+
+config HYPERV_ROOT_IOMMU
+	bool "Hyper-V root VM IOMMU Device"
+	depends on HYPERV && X86
+	select IOMMU_API
+	default HYPERV
+	help
+	  This enables Hyper-V pseudo IOMMU device on a root VM. When running
+          as privileged VM aka root on Microsoft Hyper-V hypervisor, this must
+          be enabled for doing any PCI passthru of devices to guest VMs. This
+          applies to both PFs and VFs. When enabling this, it is best to
+          disable amd/intel iommus via: intel_iommu=off amd_iommu=off as
+          the hypervisor really owns the iommu.
diff --git a/drivers/iommu/hyperv/Makefile b/drivers/iommu/hyperv/Makefile
index 6ef0ef97f3dd..c7e7d0dac2a4 100644
--- a/drivers/iommu/hyperv/Makefile
+++ b/drivers/iommu/hyperv/Makefile
@@ -1,2 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_IRQ_REMAP) += hv-irq-remap-x86.o
+obj-$(CONFIG_HYPERV_ROOT_IOMMU) += hv-iommu-root.o
diff --git a/drivers/iommu/hyperv/hv-iommu-root.c b/drivers/iommu/hyperv/hv-iommu-root.c
new file mode 100644
index 000000000000..a5268e0e52cc
--- /dev/null
+++ b/drivers/iommu/hyperv/hv-iommu-root.c
@@ -0,0 +1,645 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Hyper-V root vIOMMU driver.
+ * Copyright (C) 2026, Microsoft, Inc.
+ */
+#include <linux/pci.h>
+#include <linux/dma-map-ops.h>
+#include <linux/interval_tree.h>
+#include <linux/hyperv.h>
+#include <asm/iommu.h>
+#include <asm/mshyperv.h>
+#include "../dma-iommu.h"
+
+/*
+ * We will not claim these PCI devices. Eg hypervisor debugger is using it
+ * for a dynamic debug session. They cannot be enumerated under static ACPI
+ * device scope.
+ */
+static char *hv_skip_pci_devs;
+static int __init hv_iommu_setup_skip(char *str)
+{
+	hv_skip_pci_devs = str;
+	return 1;
+}
+/* Eg: hv_iommu_skip=(SSSS:BB:DD.F)(SSSS:BB:DD.F) */
+__setup("hv_iommu_skip=", hv_iommu_setup_skip);
+
+static dma_addr_t hv_max_iova_width;
+static struct iommu_domain_ops hv_paging_domain_ops;
+
+/* IOMMU device that we export to the world. HyperV supports max of one */
+static struct iommu_device hv_virt_iommu;
+
+struct hv_domain {
+	struct iommu_domain iommu_dom;
+	u32 domid_num;			      /* as opposed to domain_id.type */
+	spinlock_t mappings_lock;	      /* protects mappings_tree */
+	struct rb_root_cached mappings_tree;  /* iova to pa lookup tree */
+};
+
+#define to_hv_domain(d) container_of(d, struct hv_domain, iommu_dom)
+
+struct hv_iommu_mapping {
+	phys_addr_t paddr;
+	struct interval_tree_node iova;
+	u32 flags;
+};
+
+/*
+ * By default, during boot the hypervisor creates one Stage 2 (S2) default
+ * domain. It has two types:
+ *   S2 default: access to entire root partition memory. This for the host
+ *               maps to IOMMU_DOMAIN_IDENTITY in the iommu subsystem, and
+ *               is called HV_DEVICE_DOMAIN_ID_S2_DEFAULT in the hypervisor.
+ *   S2 NULL: Blocks everything, ie, IOMMU_DOMAIN_BLOCKED in linux.
+ */
+
+/*
+ * Create dummy domains to correspond to hypervisor prebuilt default identity
+ * and null domains (dummy because we do not make hypercalls to create them).
+ */
+static struct hv_domain hv_def_identity_dom;
+static struct hv_domain hv_def_blocked_dom;
+
+static bool hv_special_domain(struct hv_domain *hvdom)
+{
+	return hvdom == &hv_def_identity_dom || hvdom == &hv_def_blocked_dom;
+}
+
+#define HV_IOMMU_PGSIZES SZ_4K		/* for now, to be enhanced */
+static atomic_t hv_unique_id;		/* unique numeric id for a new domain */
+
+static bool hv_iommu_capable(struct device *dev, enum iommu_cap cap)
+{
+	switch (cap) {
+	case IOMMU_CAP_CACHE_COHERENCY:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static int hv_iommu_add_tree_mapping(struct hv_domain *hvdom,
+				     unsigned long iova, phys_addr_t paddr,
+				     size_t size, u32 flags)
+{
+	unsigned long irqflags;
+	struct hv_iommu_mapping *mapping;
+
+	mapping = kzalloc_obj(struct hv_iommu_mapping, GFP_ATOMIC);
+	if (!mapping)
+		return -ENOMEM;
+
+	mapping->paddr = paddr;
+	mapping->iova.start = iova;
+	mapping->iova.last = iova + size - 1;
+	mapping->flags = flags;
+
+	spin_lock_irqsave(&hvdom->mappings_lock, irqflags);
+	interval_tree_insert(&mapping->iova, &hvdom->mappings_tree);
+	spin_unlock_irqrestore(&hvdom->mappings_lock, irqflags);
+
+	return 0;
+}
+
+/* If size == 0, then last = ULONG_MAX. With iova 0, will remove everything */
+static size_t hv_iommu_del_tree_mappings(struct hv_domain *hvdom,
+					 unsigned long iova, size_t size)
+{
+	unsigned long flags;
+	size_t unmapped = 0;
+	unsigned long last = iova + size - 1;
+	struct hv_iommu_mapping *mapping = NULL;
+	struct interval_tree_node *node, *next;
+
+	spin_lock_irqsave(&hvdom->mappings_lock, flags);
+	next = interval_tree_iter_first(&hvdom->mappings_tree, iova, last);
+	while (next) {
+		node = next;
+		mapping = container_of(node, struct hv_iommu_mapping, iova);
+		next = interval_tree_iter_next(node, iova, last);
+
+		/* Splitting of a mapping is not supported at present */
+		if (mapping->iova.start < iova)
+			break;
+
+		unmapped += mapping->iova.last - mapping->iova.start + 1;
+
+		interval_tree_remove(node, &hvdom->mappings_tree);
+		kfree(mapping);
+	}
+	spin_unlock_irqrestore(&hvdom->mappings_lock, flags);
+
+	return unmapped;
+}
+
+/* Create a new device domain in the hypervisor */
+static int hv_iommu_create_hyp_devdom(struct hv_domain *hvdom)
+{
+	u64 status;
+	struct hv_input_device_domain *ddp;
+	struct hv_input_create_device_domain *input;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	memset(input, 0, sizeof(*input));
+
+	ddp = &input->device_domain;
+	ddp->partition_id = HV_PARTITION_ID_SELF;
+	ddp->domain_id.type = HV_DEVICE_DOMAIN_TYPE_S2;
+	ddp->domain_id.id = hvdom->domid_num;
+
+	input->create_device_domain_flags.forward_progress_required = 1;
+	input->create_device_domain_flags.inherit_owning_vtl = 0;
+
+	status = hv_do_hypercall(HVCALL_CREATE_DEVICE_DOMAIN, input, NULL);
+
+	local_irq_restore(flags);
+
+	if (!hv_result_success(status))
+		hv_status_err(status, "\n");
+
+	return hv_result_to_errno(status);
+}
+
+static struct iommu_domain *hv_iommu_domain_alloc_paging(struct device *dev)
+{
+	struct hv_domain *hvdom;
+	int rc;
+	u32 unique_id;
+
+	if (!dev_is_pci(dev))
+		return NULL;
+
+	hvdom = kzalloc_obj(struct hv_domain);
+	if (hvdom == NULL)
+		return NULL;
+
+	spin_lock_init(&hvdom->mappings_lock);
+	hvdom->mappings_tree = RB_ROOT_CACHED;
+
+	unique_id = (u32)atomic_inc_return(&hv_unique_id);
+	if (unique_id == HV_DEVICE_DOMAIN_ID_S2_NULL)	/* ie, UINTMAX */
+		goto out_err;
+
+	hvdom->domid_num = unique_id;
+
+	hvdom->iommu_dom.pgsize_bitmap = HV_IOMMU_PGSIZES;
+	hvdom->iommu_dom.geometry.aperture_start = 0;
+	hvdom->iommu_dom.geometry.aperture_end = hv_max_iova_width;
+	hvdom->iommu_dom.geometry.force_aperture = true;
+	hvdom->iommu_dom.ops = &hv_paging_domain_ops;
+
+	rc = hv_iommu_create_hyp_devdom(hvdom);
+	if (rc)
+		goto out_err;
+
+	return &hvdom->iommu_dom;
+
+out_err:
+	kfree(hvdom);
+	return NULL;
+}
+
+static void hv_iommu_domain_free(struct iommu_domain *immdom)
+{
+	unsigned long flags;
+	u64 status;
+	struct hv_input_delete_device_domain *input;
+	struct hv_input_device_domain *ddp;
+	struct hv_domain *hvdom = to_hv_domain(immdom);
+
+	if (hv_special_domain(hvdom))
+		return;
+
+	/* Cleanup any remaining. 0 for size results in ULONG_MAX as the last */
+	hv_iommu_del_tree_mappings(hvdom, 0, 0);
+
+	local_irq_save(flags);
+	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	ddp = &input->device_domain;
+	memset(input, 0, sizeof(*input));
+
+	ddp->partition_id = HV_PARTITION_ID_SELF;
+	ddp->domain_id.type = HV_DEVICE_DOMAIN_TYPE_S2;
+	ddp->domain_id.id = hvdom->domid_num;
+
+	status = hv_do_hypercall(HVCALL_DELETE_DEVICE_DOMAIN, input,
+				 NULL);
+	local_irq_restore(flags);
+
+	if (!hv_result_success(status))
+		hv_status_err(status, "\n");
+
+	kfree(hvdom);
+}
+
+/*
+ * Attach a device to the default domain, or the null domain, or to a domain
+ * previously created in the hypervisor.
+ */
+static int hv_iommu_att_dev2dom(struct hv_domain *hvdom, struct pci_dev *pdev)
+{
+	unsigned long flags;
+	u64 status;
+	struct hv_input_attach_device_domain *input;
+
+	local_irq_save(flags);
+	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	memset(input, 0, sizeof(*input));
+
+	/* For null domain, hvdom->domid_num == HV_DEVICE_DOMAIN_ID_S2_NULL */
+	input->device_domain.partition_id = HV_PARTITION_ID_SELF;
+	input->device_domain.domain_id.type = HV_DEVICE_DOMAIN_TYPE_S2;
+	input->device_domain.domain_id.id = hvdom->domid_num;
+
+	input->device_id.as_uint64 = hv_build_devid_type_pci(pdev);
+
+	status = hv_do_hypercall(HVCALL_ATTACH_DEVICE_DOMAIN, input, NULL);
+	local_irq_restore(flags);
+
+	if (!hv_result_success(status))
+		hv_status_err(status, "\n");
+
+	return hv_result_to_errno(status);
+}
+
+static int hv_iommu_attach_dev(struct iommu_domain *immdom, struct device *dev,
+			       struct iommu_domain *old)
+{
+	struct pci_dev *pdev;
+	int rc;
+	struct hv_domain *hvdom_new = to_hv_domain(immdom);
+
+	if (!dev_is_pci(dev))
+		return -EINVAL;
+
+	pdev = to_pci_dev(dev);
+
+	rc = hv_iommu_att_dev2dom(hvdom_new, pdev);
+	if (rc)
+		WARN(1, "Failed to attach pdev:%s\n", pci_name(pdev));
+
+	return rc;
+}
+
+static u64 hv_iommu_unmap_batch(u32 domid_num, ulong iova, u16 count)
+{
+	ulong flags;
+	struct hv_input_unmap_device_gpa_pages *input;
+	u64 status;
+
+	local_irq_save(flags);
+	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	memset(input, 0, sizeof(*input));
+
+	input->device_domain.partition_id = HV_PARTITION_ID_SELF;
+	input->device_domain.domain_id.type = HV_DEVICE_DOMAIN_TYPE_S2;
+	input->device_domain.domain_id.id = domid_num;
+	input->target_device_va_base = iova;
+
+	status = hv_do_rep_hypercall(HVCALL_UNMAP_DEVICE_GPA_PAGES, count,
+				     0, input, NULL);
+	local_irq_restore(flags);
+
+	if (!hv_result_success(status))
+		hv_status_err(status, "iova:0x%lx count:0x%x\n", iova, count);
+
+	return status;
+}
+
+static size_t hv_iommu_unmap_pages(struct iommu_domain *immdom, ulong iova,
+				   size_t pgsize, size_t pgcount,
+				   struct iommu_iotlb_gather *gather)
+{
+	unsigned long npages;
+	u64 status;
+	struct hv_domain *hvdom = to_hv_domain(immdom);
+	size_t unmapped, tot_done = 0, size = pgsize * pgcount;
+
+	unmapped = hv_iommu_del_tree_mappings(hvdom, iova, size);
+	if (unmapped < size)
+		pr_err("%s: could not delete all mappings (%lx:%lx/%lx)\n",
+		       __func__, iova, unmapped, size);
+
+	npages = unmapped >> HV_HYP_PAGE_SHIFT;
+
+	while (npages) {
+		int done, count = min(npages, HV_REP_COUNT_MAX);
+
+		status = hv_iommu_unmap_batch(hvdom->domid_num, iova, count);
+
+		done = hv_repcomp(status);
+		tot_done += done;
+		npages -= done;
+		iova += done << HV_HYP_PAGE_SHIFT;
+
+		if (!hv_result_success(status))
+			break;
+	}
+
+	return tot_done << HV_HYP_PAGE_SHIFT;
+}
+
+/* Return: must return exact status from the hypercall without changes */
+static u64 hv_iommu_map_pgs(struct hv_domain *hvdom,
+			    unsigned long iova, phys_addr_t paddr,
+			    unsigned long npages, u32 map_flags)
+{
+	u64 status;
+	int i;
+	struct hv_input_map_device_gpa_pages *input;
+	unsigned long flags, pfn;
+
+	local_irq_save(flags);
+	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	memset(input, 0, sizeof(*input));
+
+	input->device_domain.partition_id = HV_PARTITION_ID_SELF;
+	input->device_domain.domain_id.type = HV_DEVICE_DOMAIN_TYPE_S2;
+	input->device_domain.domain_id.id = hvdom->domid_num;
+	input->map_flags = map_flags;
+	input->target_device_va_base = iova;
+
+	pfn = paddr >> HV_HYP_PAGE_SHIFT;
+	for (i = 0; i < npages; i++, pfn++)
+		input->gpa_page_list[i] = pfn;
+
+	status = hv_do_rep_hypercall(HVCALL_MAP_DEVICE_GPA_PAGES, npages, 0,
+				     input, NULL);
+	local_irq_restore(flags);
+
+	return status;
+}
+
+#define HV_MAP_DEVICE_GPA_BATCH_SIZE   \
+	((HV_HYP_PAGE_SIZE - sizeof(struct hv_input_map_device_gpa_pages)) \
+			/ sizeof(u64))
+
+/*
+ * The core VFIO code loops over memory ranges calling this function with the
+ * largest pgsize from HV_IOMMU_PGSIZES. cond_resched() is in vfio_iommu_map.
+ */
+static int hv_iommu_map_pages(struct iommu_domain *immdom, ulong iova,
+			      phys_addr_t paddr, size_t pgsize, size_t pgcount,
+			      int prot, gfp_t gfp, size_t *mapped)
+{
+	u32 map_flags;
+	int ret;
+	u64 status;
+	unsigned long npages, done = 0;
+	struct hv_domain *hvdom = to_hv_domain(immdom);
+	size_t size = pgsize * pgcount;
+
+	map_flags = HV_MAP_GPA_READABLE;	/* required */
+	map_flags |= prot & IOMMU_WRITE ? HV_MAP_GPA_WRITABLE : 0;
+
+	ret = hv_iommu_add_tree_mapping(hvdom, iova, paddr, size, map_flags);
+	if (ret)
+		return ret;
+
+	npages = size >> HV_HYP_PAGE_SHIFT;
+	while (done < npages) {
+		ulong completed, remain = npages - done;
+
+		remain = min(remain, HV_MAP_DEVICE_GPA_BATCH_SIZE);
+
+		status = hv_iommu_map_pgs(hvdom, iova, paddr, remain,
+					  map_flags);
+
+		completed = hv_repcomp(status);
+		done = done + completed;
+		iova = iova + (completed << HV_HYP_PAGE_SHIFT);
+		paddr = paddr + (completed << HV_HYP_PAGE_SHIFT);
+
+		if (hv_result(status) == HV_STATUS_INSUFFICIENT_MEMORY) {
+			ret = hv_call_deposit_pages(NUMA_NO_NODE,
+						    hv_current_partition_id,
+						    256);
+			if (ret)
+				break;
+			continue;
+		}
+		if (!hv_result_success(status))
+			break;
+	}
+
+	if (!hv_result_success(status)) {
+		size_t done_size = done << HV_HYP_PAGE_SHIFT;
+
+		hv_status_err(status, "pgs:%lx/%lx iova:%lx\n",
+			      done, npages, iova);
+		/*
+		 * lookup tree has all mappings [0 - size-1]. Below unmap will
+		 * only remove from [0 - done], we need to remove second chunk
+		 * [done+1 - size-1].
+		 */
+		hv_iommu_del_tree_mappings(hvdom, iova, size - done_size);
+		hv_iommu_unmap_pages(immdom, iova - done_size, HV_HYP_PAGE_SIZE,
+				     done, NULL);
+		if (mapped)
+			*mapped = 0;
+	} else
+		if (mapped)
+			*mapped = size;
+
+	return hv_result_to_errno(status);
+}
+
+static phys_addr_t hv_iommu_iova_to_phys(struct iommu_domain *immdom,
+					 dma_addr_t iova)
+{
+	unsigned long flags;
+	struct hv_iommu_mapping *mapping;
+	struct interval_tree_node *node;
+	u64 paddr = 0;
+	struct hv_domain *hvdom = to_hv_domain(immdom);
+
+	spin_lock_irqsave(&hvdom->mappings_lock, flags);
+	node = interval_tree_iter_first(&hvdom->mappings_tree, iova, iova);
+	if (node) {
+		mapping = container_of(node, struct hv_iommu_mapping, iova);
+		paddr = mapping->paddr + (iova - mapping->iova.start);
+	}
+	spin_unlock_irqrestore(&hvdom->mappings_lock, flags);
+
+	return paddr;
+}
+
+/*
+ * Currently, hypervisor does not provide list of devices it is using
+ * dynamically. So use this to allow users to manually specify devices that
+ * should be skipped. (eg. hypervisor debugger using some network device).
+ */
+static struct iommu_device *hv_iommu_probe_device(struct device *dev)
+{
+	if (!dev_is_pci(dev))
+		return ERR_PTR(-ENODEV);
+
+	if (hv_skip_pci_devs && *hv_skip_pci_devs) {
+		int rc, parsed, segment, bus, slot, func;
+		int pos = 0;
+		struct pci_dev *pdev = to_pci_dev(dev);
+
+		do {
+			parsed = 0;
+
+			rc = sscanf(hv_skip_pci_devs + pos, " (%x:%x:%x.%x) %n",
+				    &segment, &bus, &slot, &func, &parsed);
+
+			if (rc != 4 || parsed <= 0)
+				break;
+
+			if (pci_domain_nr(pdev->bus) == segment &&
+			    pdev->bus->number == bus &&
+			    PCI_SLOT(pdev->devfn) == slot &&
+			    PCI_FUNC(pdev->devfn) == func) {
+
+				dev_info(dev, "skipped by Hyper-V IOMMU\n");
+				return ERR_PTR(-ENODEV);
+			}
+			pos += parsed;
+
+		} while (hv_skip_pci_devs[pos]);
+	}
+
+	return &hv_virt_iommu;
+}
+
+static struct iommu_group *hv_iommu_device_group(struct device *dev)
+{
+	if (dev_is_pci(dev))
+		return pci_device_group(dev);
+
+	return generic_device_group(dev);
+}
+
+static void hv_iommu_get_resv_regions(struct device *dev,
+				      struct list_head *head)
+{
+	struct iommu_resv_region *reg;
+
+	/* reserve the entire LAPIC region */
+	reg = iommu_alloc_resv_region(0xfee00000, SZ_1M, 0, IOMMU_RESV_MSI,
+				      GFP_KERNEL);
+	if (reg)
+		list_add_tail(&reg->list, head);
+}
+
+static struct iommu_domain_ops hv_paging_domain_ops = {
+	.attach_dev = hv_iommu_attach_dev,
+	.map_pages = hv_iommu_map_pages,
+	.unmap_pages = hv_iommu_unmap_pages,
+	.iova_to_phys = hv_iommu_iova_to_phys,
+	.free = hv_iommu_domain_free,
+};
+
+static struct iommu_ops hv_iommu_ops = {
+	.capable	    = hv_iommu_capable,
+	.domain_alloc_paging	= hv_iommu_domain_alloc_paging,
+	.probe_device	    = hv_iommu_probe_device,
+	.device_group	    = hv_iommu_device_group,
+	.get_resv_regions   = hv_iommu_get_resv_regions,
+	.owner		    = THIS_MODULE,
+	.identity_domain    = &hv_def_identity_dom.iommu_dom,
+	.blocked_domain     = &hv_def_blocked_dom.iommu_dom,
+};
+
+static const struct iommu_domain_ops hv_special_domain_ops = {
+	.attach_dev = hv_iommu_attach_dev,
+};
+
+static void __init hv_initialize_special_domains(void)
+{
+	hv_def_identity_dom.iommu_dom.type = IOMMU_DOMAIN_IDENTITY;
+	hv_def_identity_dom.iommu_dom.ops = &hv_special_domain_ops;
+	hv_def_identity_dom.iommu_dom.owner = &hv_iommu_ops;
+	hv_def_identity_dom.domid_num = HV_DEVICE_DOMAIN_ID_S2_DEFAULT; /* 0 */
+
+	hv_def_blocked_dom.iommu_dom.type = IOMMU_DOMAIN_BLOCKED;
+	hv_def_blocked_dom.iommu_dom.ops = &hv_special_domain_ops;
+	hv_def_blocked_dom.iommu_dom.owner = &hv_iommu_ops;
+	hv_def_blocked_dom.domid_num = HV_DEVICE_DOMAIN_ID_S2_NULL; /* INTMAX */
+}
+
+
+static int hv_iommu_get_caps(struct hv_output_get_iommu_capabilities *caps)
+{
+	u64 status;
+	unsigned long flags;
+	struct hv_input_get_iommu_capabilities *input;
+	struct hv_output_get_iommu_capabilities *output;
+
+	local_irq_save(flags);
+
+	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	output = *this_cpu_ptr(hyperv_pcpu_output_arg);
+	memset(input, 0, sizeof(*input));
+	input->partition_id = HV_PARTITION_ID_SELF;
+	status = hv_do_hypercall(HVCALL_GET_IOMMU_CAPABILITIES, input, output);
+	*caps = *output;
+
+	local_irq_restore(flags);
+
+	if (!hv_result_success(status))
+		hv_status_err(status, "\n");
+
+	return hv_result_to_errno(status);
+}
+
+static int __init hv_iommu_init(void)
+{
+	int rc;
+	struct iommu_device *iommup = &hv_virt_iommu;
+	struct hv_output_get_iommu_capabilities caps;
+
+	if (!hv_is_hyperv_initialized())
+		return -ENODEV;
+
+	rc = hv_iommu_get_caps(&caps);
+	if (rc)
+		return rc;
+
+	hv_max_iova_width = caps.max_iova_width;
+
+	rc = iommu_device_sysfs_add(iommup, NULL, NULL, "%s", "hyperv-iommu");
+	if (rc) {
+		pr_err("Hyper-V: iommu_device_sysfs_add failed: %d\n", rc);
+		return rc;
+	}
+
+	/* This must come before iommu_device_register() because the latter
+	 * calls into the hooks.
+	 */
+	hv_initialize_special_domains();
+
+	rc = iommu_device_register(iommup, &hv_iommu_ops, NULL);
+	if (rc) {
+		pr_err("Hyper-V: iommu_device_register failed: %d\n", rc);
+		goto err_sysfs_remove;
+	}
+
+	pr_info("Hyper-V IOMMU initialized\n");
+
+	return 0;
+
+err_sysfs_remove:
+	iommu_device_sysfs_remove(iommup);
+	return rc;
+}
+
+void __init hv_iommu_detect(void)
+{
+	if (no_iommu || iommu_detected || hv_l1vh_partition())
+		return;
+
+	if (!(ms_hyperv.misc_features & HV_DEVICE_DOMAIN_AVAILABLE))
+		return;
+
+	iommu_detected = 1;
+	x86_init.iommu.iommu_init = hv_iommu_init;
+
+	pci_request_acs();
+}
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index bf601d67cecb..fa8331c7c3a2 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -28,6 +28,9 @@
 
 #define VTPM_BASE_ADDRESS 0xfed40000
 
+#define HV_REP_COUNT_MAX        \
+	(HV_HYPERCALL_REP_COMP_MASK >> HV_HYPERCALL_REP_COMP_OFFSET)
+
 enum hv_partition_type {
 	HV_PARTITION_TYPE_GUEST,
 	HV_PARTITION_TYPE_ROOT,
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 9e109d91aa14..01a69f88cfa7 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1783,4 +1783,10 @@ static inline unsigned long virt_to_hvpfn(void *addr)
 #define HVPFN_DOWN(x)	((x) >> HV_HYP_PAGE_SHIFT)
 #define page_to_hvpfn(page)	(page_to_pfn(page) * NR_HV_HYP_PAGES_IN_PAGE)
 
+#ifdef CONFIG_HYPERV_ROOT_IOMMU
+void __init hv_iommu_detect(void);
+#else
+static inline void hv_iommu_detect(void) { }
+#endif /* CONFIG_HYPERV_ROOT_IOMMU */
+
 #endif /* _HYPERV_H */
-- 
2.51.2.vfs.0.1