[PATCH V4 7/9] x86/hyperv: Implement Hyper-V virtual IOMMU

[Mukesh R <mrathor@linux.microsoft.com>]

Add a new file to implement a virtual IOMMU that works with Microsoft
Hyper-V hypervisor. The hypervisor claims the IOMMU upon boot, and this
driver communicates with it for creating and deleting paging domains,
mapping and unmapping of pages, etc. The default domain type is IDENTITY.
Lastly, this is only supported on baremetal or nested root/dom0, and not
L1VH root/dom0.

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 | 704 +++++++++++++++++++++++++++
 include/asm-generic/mshyperv.h       |   3 +
 include/linux/hyperv.h               |   6 +
 7 files changed, 732 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 1becc0f20222..e95a56a6e075 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..512b154b2f59
--- /dev/null
+++ b/drivers/iommu/hyperv/Kconfig
@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# Hyper-V IOMMU support
+
+config HYPERV_IOMMU
+	bool "Hyper-V IOMMU Device"
+	depends on HYPERV && X86
+	select IOMMU_API
+	default HYPERV
+	help
+	  This enables Hyper-V pseudo IOMMU device. 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..aaced370a94f 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_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..374fa0c177c6
--- /dev/null
+++ b/drivers/iommu/hyperv/hv-iommu-root.c
@@ -0,0 +1,704 @@
+// 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 needs it for debugger */
+static char *pci_devs_to_skip;
+static int __init hv_iommu_setup_skip(char *str)
+{
+	pci_devs_to_skip = str;
+
+	return 0;
+}
+/* hv_iommu_skip=(SSSS:BB:DD.F)(SSSS:BB:DD.F) */
+__setup("hv_iommu_skip=", hv_iommu_setup_skip);
+
+/* 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 */
+	u64 partid;			      /* partition id */
+	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. Stage 2 means that the page table is controlled by the hypervisor.
+ * It has two types:
+ *   S2 default: access to entire root partition memory. This for us easily
+ *		 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 except RMRR
+ */
+
+/*
+ * 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_null_dom;
+
+static bool hv_special_domain(struct hv_domain *hvdom)
+{
+	return hvdom == &hv_def_identity_dom || hvdom == &hv_null_dom;
+}
+
+struct iommu_domain_geometry default_geometry = (struct iommu_domain_geometry) {
+	.aperture_start = 0,
+	.aperture_end = -1UL,
+	.force_aperture = true,
+};
+
+#define HV_IOMMU_PGSIZES SZ_4K	/* for now, to be enhanced */
+
+static atomic_t hv_unique_id;		/* unique numeric id for a new domain */
+
+/*
+ * If the current thread is a VMM thread, return the partition id of the VM it
+ * is managing, else return HV_PARTITION_ID_INVALID.
+ */
+static u64 hv_get_current_partid(void)
+{
+	u64 (*fn)(void);
+	u64 ptid;
+
+	fn = symbol_get(mshv_current_partid);
+	if (!fn)
+		return HV_PARTITION_ID_INVALID;
+
+	ptid = fn();
+	symbol_put(mshv_current_partid);
+
+	return ptid;
+}
+
+static bool hv_iommu_capable(struct device *dev, enum iommu_cap cap)
+{
+	switch (cap) {
+	case IOMMU_CAP_CACHE_COHERENCY:
+		return true;
+	default:
+		return false;
+	}
+}
+
+/* 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;
+	u64 ptid = hv_get_current_partid();
+
+	if (ptid == HV_PARTITION_ID_INVALID)
+		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->partid = ptid;
+	hvdom->iommu_dom.geometry = default_geometry;
+	hvdom->iommu_dom.pgsize_bitmap = HV_IOMMU_PGSIZES;
+
+	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;
+
+	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);
+}
+
+static void hv_iommu_det_dev_from_dom(struct pci_dev *pdev)
+{
+	u64 status;
+	unsigned long flags;
+	struct hv_input_detach_device_domain *input;
+
+	local_irq_save(flags);
+	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
+	memset(input, 0, sizeof(*input));
+
+	input->partition_id = HV_PARTITION_ID_SELF;
+	input->device_id.as_uint64 = hv_build_devid_type_pci(pdev);
+	status = hv_do_hypercall(HVCALL_DETACH_DEVICE_DOMAIN, input, NULL);
+	local_irq_restore(flags);
+
+	if (!hv_result_success(status))
+		hv_status_err(status, "\n");
+}
+
+static void hv_iommu_detach_dev(struct hv_domain *hvdom, struct device *dev)
+{
+	struct pci_dev *pdev;
+
+	/* See the attach function, only PCI devices for now */
+	if (!dev_is_pci(dev))
+		return;
+
+	pdev = to_pci_dev(dev);
+	hv_iommu_det_dev_from_dom(pdev);
+}
+
+/*
+ * 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;
+
+	/* NB: Upon guest shutdown, device is re-attached to the default domain
+	 *     without explicit detach.
+	 */
+	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);
+}
+
+/* Attach a device for passthru to guest VMs, host apps like SPDK, etc */
+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);
+	struct hv_domain *hvdom_prev = to_hv_domain(old);
+
+	/* Only allow PCI devices for now */
+	if (!dev_is_pci(dev))
+		return -EINVAL;
+
+	pdev = to_pci_dev(dev);
+
+	/* There are no explicit detach calls, hence check first if we need
+	 * to detach first. Also, in case of guest shutdown, it's the VMM
+	 * thread that attaches it back to the hv_def_identity_dom, and
+	 * hvdom_prev will not be null then. It is null during boot.
+	 */
+	if (hvdom_prev && !hv_special_domain(hvdom_prev))
+		hv_iommu_detach_dev(hvdom_prev, dev);
+
+	rc = hv_iommu_att_dev2dom(hvdom_new, pdev);
+
+	if (rc == 0)
+		dev_iommu_priv_set(dev, hvdom_new);  /* sets "private" field */
+	else
+		dev_iommu_priv_set(dev, NULL);
+
+	return rc;
+}
+
+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);
+	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;
+}
+
+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);
+
+		/* Trying to split a mapping? Not supported for now. */
+		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;
+}
+
+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);
+		size = unmapped;
+	}
+
+	npages = size >> 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 (pci_devs_to_skip && *pci_devs_to_skip) {
+		int rc, pos = 0;
+		int parsed;
+		int segment, bus, slot, func;
+		struct pci_dev *pdev = to_pci_dev(dev);
+
+		do {
+			parsed = 0;
+
+			rc = sscanf(pci_devs_to_skip + pos, " (%x:%x:%x.%x) %n",
+				    &segment, &bus, &slot, &func, &parsed);
+			if (rc)
+				break;
+			if (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 (pci_devs_to_skip[pos]);
+	}
+
+	/* Device will be explicitly attached to the default domain, so no need
+	 * to do dev_iommu_priv_set() here.
+	 */
+
+	return &hv_virt_iommu;
+}
+
+static void hv_iommu_probe_finalize(struct device *dev)
+{
+	struct iommu_domain *immdom = iommu_get_domain_for_dev(dev);
+
+	if (immdom && immdom->type == IOMMU_DOMAIN_DMA)
+		iommu_setup_dma_ops(dev, immdom);
+	else
+		set_dma_ops(dev, NULL);
+}
+
+static void hv_iommu_release_device(struct device *dev)
+{
+	struct hv_domain *hvdom = dev_iommu_priv_get(dev);
+
+	/* Need to detach device from device domain if necessary. */
+	if (hvdom)
+		hv_iommu_detach_dev(hvdom, dev);
+
+	dev_iommu_priv_set(dev, NULL);
+	set_dma_ops(dev, NULL);
+}
+
+static struct iommu_group *hv_iommu_device_group(struct device *dev)
+{
+	if (dev_is_pci(dev))
+		return pci_device_group(dev);
+	else
+		return generic_device_group(dev);
+}
+
+static int hv_iommu_def_domain_type(struct device *dev)
+{
+	/* The hypervisor always creates this by default during boot */
+	return IOMMU_DOMAIN_IDENTITY;
+}
+
+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,
+	.probe_finalize     = hv_iommu_probe_finalize,
+	.release_device     = hv_iommu_release_device,
+	.def_domain_type    = hv_iommu_def_domain_type,
+	.device_group	    = hv_iommu_device_group,
+	.default_domain_ops = &(const struct iommu_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,
+	},
+	.owner		    = THIS_MODULE,
+	.identity_domain = &hv_def_identity_dom.iommu_dom,
+	.blocked_domain  = &hv_null_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.iommu_dom.geometry = default_geometry;
+	hv_def_identity_dom.domid_num = HV_DEVICE_DOMAIN_ID_S2_DEFAULT; /* 0 */
+
+	hv_null_dom.iommu_dom.type = IOMMU_DOMAIN_BLOCKED;
+	hv_null_dom.iommu_dom.ops = &hv_special_domain_ops;
+	hv_null_dom.iommu_dom.owner = &hv_iommu_ops;
+	hv_null_dom.iommu_dom.geometry = default_geometry;
+	hv_null_dom.domid_num = HV_DEVICE_DOMAIN_ID_S2_NULL;  /* INTMAX */
+}
+
+static int __init hv_iommu_init(void)
+{
+	int ret;
+	struct iommu_device *iommup = &hv_virt_iommu;
+
+	if (!hv_is_hyperv_initialized())
+		return -ENODEV;
+
+	ret = iommu_device_sysfs_add(iommup, NULL, NULL, "%s", "hyperv-iommu");
+	if (ret) {
+		pr_err("Hyper-V: iommu_device_sysfs_add failed: %d\n", ret);
+		return ret;
+	}
+
+	/* This must come before iommu_device_register() because the latter
+	 * calls into the hooks.
+	 */
+	hv_initialize_special_domains();
+
+	ret = iommu_device_register(iommup, &hv_iommu_ops, NULL);
+	if (ret) {
+		pr_err("Hyper-V: iommu_device_register failed: %d\n", ret);
+		goto err_sysfs_remove;
+	}
+
+	pr_info("Hyper-V IOMMU initialized\n");
+
+	return 0;
+
+err_sysfs_remove:
+	iommu_device_sysfs_remove(iommup);
+	return ret;
+}
+
+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 e8cbc4e3f7ad..2c5d0812f19d 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 964f1be8150c..f78645e8d776 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1769,4 +1769,10 @@ 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_IOMMU
+void __init hv_iommu_detect(void);
+#else
+static inline void hv_iommu_detect(void) { }
+#endif /* CONFIG_HYPERV_IOMMU */
+
 #endif /* _HYPERV_H */
-- 
2.51.2.vfs.0.1