diff --git a/drivers/ntb/Kconfig b/drivers/ntb/Kconfig
index 95944e52fa36..5760764052be 100644
--- a/drivers/ntb/Kconfig
+++ b/drivers/ntb/Kconfig
@@ -12,6 +12,17 @@ menuconfig NTB
 
 if NTB
 
+config NTB_MSI
+	bool "MSI Interrupt Support"
+	depends on PCI_MSI
+	help
+	 Support using MSI interrupt forwarding instead of (or in addition to)
+	 hardware doorbells. MSI interrupts typically offer lower latency
+	 than doorbells and more MSI interrupts can be made available to
+	 clients. However this requires an extra memory window and support
+	 in the hardware driver for creating the MSI interrupts.
+
+	 If unsure, say N.
 source "drivers/ntb/hw/Kconfig"
 
 source "drivers/ntb/test/Kconfig"
diff --git a/drivers/ntb/Makefile b/drivers/ntb/Makefile
index 537226f8e78d..cc27ad2ef150 100644
--- a/drivers/ntb/Makefile
+++ b/drivers/ntb/Makefile
@@ -1,4 +1,5 @@
 obj-$(CONFIG_NTB) += ntb.o hw/ test/
 obj-$(CONFIG_NTB_TRANSPORT) += ntb_transport.o
 
-ntb-y := core.o
+ntb-y			:= core.o
+ntb-$(CONFIG_NTB_MSI)	+= msi.o
diff --git a/drivers/ntb/msi.c b/drivers/ntb/msi.c
new file mode 100644
index 000000000000..9dddf133658f
--- /dev/null
+++ b/drivers/ntb/msi.c
@@ -0,0 +1,415 @@
+// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
+
+#include <linux/irq.h>
+#include <linux/module.h>
+#include <linux/ntb.h>
+#include <linux/msi.h>
+#include <linux/pci.h>
+
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_VERSION("0.1");
+MODULE_AUTHOR("Logan Gunthorpe <logang@deltatee.com>");
+MODULE_DESCRIPTION("NTB MSI Interrupt Library");
+
+struct ntb_msi {
+	u64 base_addr;
+	u64 end_addr;
+
+	void (*desc_changed)(void *ctx);
+
+	u32 __iomem *peer_mws[];
+};
+
+/**
+ * ntb_msi_init() - Initialize the MSI context
+ * @ntb:	NTB device context
+ *
+ * This function must be called before any other ntb_msi function.
+ * It initializes the context for MSI operations and maps
+ * the peer memory windows.
+ *
+ * This function reserves the last N outbound memory windows (where N
+ * is the number of peers).
+ *
+ * Return: Zero on success, otherwise a negative error number.
+ */
+int ntb_msi_init(struct ntb_dev *ntb,
+		 void (*desc_changed)(void *ctx))
+{
+	phys_addr_t mw_phys_addr;
+	resource_size_t mw_size;
+	size_t struct_size;
+	int peer_widx;
+	int peers;
+	int ret;
+	int i;
+
+	peers = ntb_peer_port_count(ntb);
+	if (peers <= 0)
+		return -EINVAL;
+
+	struct_size = sizeof(*ntb->msi) + sizeof(*ntb->msi->peer_mws) * peers;
+
+	ntb->msi = devm_kzalloc(&ntb->dev, struct_size, GFP_KERNEL);
+	if (!ntb->msi)
+		return -ENOMEM;
+
+	ntb->msi->desc_changed = desc_changed;
+
+	for (i = 0; i < peers; i++) {
+		peer_widx = ntb_peer_mw_count(ntb) - 1 - i;
+
+		ret = ntb_peer_mw_get_addr(ntb, peer_widx, &mw_phys_addr,
+					   &mw_size);
+		if (ret)
+			goto unroll;
+
+		ntb->msi->peer_mws[i] = devm_ioremap(&ntb->dev, mw_phys_addr,
+						     mw_size);
+		if (!ntb->msi->peer_mws[i]) {
+			ret = -EFAULT;
+			goto unroll;
+		}
+	}
+
+	return 0;
+
+unroll:
+	for (i = 0; i < peers; i++)
+		if (ntb->msi->peer_mws[i])
+			devm_iounmap(&ntb->dev, ntb->msi->peer_mws[i]);
+
+	devm_kfree(&ntb->dev, ntb->msi);
+	ntb->msi = NULL;
+	return ret;
+}
+EXPORT_SYMBOL(ntb_msi_init);
+
+/**
+ * ntb_msi_setup_mws() - Initialize the MSI inbound memory windows
+ * @ntb:	NTB device context
+ *
+ * This function sets up the required inbound memory windows. It should be
+ * called from a work function after a link up event.
+ *
+ * Over the entire network, this function will reserves the last N
+ * inbound memory windows for each peer (where N is the number of peers).
+ *
+ * ntb_msi_init() must be called before this function.
+ *
+ * Return: Zero on success, otherwise a negative error number.
+ */
+int ntb_msi_setup_mws(struct ntb_dev *ntb)
+{
+	struct msi_desc *desc;
+	u64 addr;
+	int peer, peer_widx;
+	resource_size_t addr_align, size_align, size_max;
+	resource_size_t mw_size = SZ_32K;
+	resource_size_t mw_min_size = mw_size;
+	int i;
+	int ret;
+
+	if (!ntb->msi)
+		return -EINVAL;
+
+	desc = first_msi_entry(&ntb->pdev->dev);
+	addr = desc->msg.address_lo + ((uint64_t)desc->msg.address_hi << 32);
+
+	for (peer = 0; peer < ntb_peer_port_count(ntb); peer++) {
+		peer_widx = ntb_peer_highest_mw_idx(ntb, peer);
+		if (peer_widx < 0)
+			return peer_widx;
+
+		ret = ntb_mw_get_align(ntb, peer, peer_widx, &addr_align,
+				       NULL, NULL);
+		if (ret)
+			return ret;
+
+		addr &= ~(addr_align - 1);
+	}
+
+	for (peer = 0; peer < ntb_peer_port_count(ntb); peer++) {
+		peer_widx = ntb_peer_highest_mw_idx(ntb, peer);
+		if (peer_widx < 0) {
+			ret = peer_widx;
+			goto error_out;
+		}
+
+		ret = ntb_mw_get_align(ntb, peer, peer_widx, NULL,
+				       &size_align, &size_max);
+		if (ret)
+			goto error_out;
+
+		mw_size = round_up(mw_size, size_align);
+		mw_size = max(mw_size, size_max);
+		if (mw_size < mw_min_size)
+			mw_min_size = mw_size;
+
+		ret = ntb_mw_set_trans(ntb, peer, peer_widx,
+				       addr, mw_size);
+		if (ret)
+			goto error_out;
+	}
+
+	ntb->msi->base_addr = addr;
+	ntb->msi->end_addr = addr + mw_min_size;
+
+	return 0;
+
+error_out:
+	for (i = 0; i < peer; i++) {
+		peer_widx = ntb_peer_highest_mw_idx(ntb, peer);
+		if (peer_widx < 0)
+			continue;
+
+		ntb_mw_clear_trans(ntb, i, peer_widx);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(ntb_msi_setup_mws);
+
+/**
+ * ntb_msi_clear_mws() - Clear all inbound memory windows
+ * @ntb:	NTB device context
+ *
+ * This function tears down the resources used by ntb_msi_setup_mws().
+ */
+void ntb_msi_clear_mws(struct ntb_dev *ntb)
+{
+	int peer;
+	int peer_widx;
+
+	for (peer = 0; peer < ntb_peer_port_count(ntb); peer++) {
+		peer_widx = ntb_peer_highest_mw_idx(ntb, peer);
+		if (peer_widx < 0)
+			continue;
+
+		ntb_mw_clear_trans(ntb, peer, peer_widx);
+	}
+}
+EXPORT_SYMBOL(ntb_msi_clear_mws);
+
+struct ntb_msi_devres {
+	struct ntb_dev *ntb;
+	struct msi_desc *entry;
+	struct ntb_msi_desc *msi_desc;
+};
+
+static int ntb_msi_set_desc(struct ntb_dev *ntb, struct msi_desc *entry,
+			    struct ntb_msi_desc *msi_desc)
+{
+	u64 addr;
+
+	addr = entry->msg.address_lo +
+		((uint64_t)entry->msg.address_hi << 32);
+
+	if (addr < ntb->msi->base_addr || addr >= ntb->msi->end_addr) {
+		dev_warn_once(&ntb->dev,
+			      "IRQ %d: MSI Address not within the memory window (%llx, [%llx %llx])\n",
+			      entry->irq, addr, ntb->msi->base_addr,
+			      ntb->msi->end_addr);
+		return -EFAULT;
+	}
+
+	msi_desc->addr_offset = addr - ntb->msi->base_addr;
+	msi_desc->data = entry->msg.data;
+
+	return 0;
+}
+
+static void ntb_msi_write_msg(struct msi_desc *entry, void *data)
+{
+	struct ntb_msi_devres *dr = data;
+
+	WARN_ON(ntb_msi_set_desc(dr->ntb, entry, dr->msi_desc));
+
+	if (dr->ntb->msi->desc_changed)
+		dr->ntb->msi->desc_changed(dr->ntb->ctx);
+}
+
+static void ntbm_msi_callback_release(struct device *dev, void *res)
+{
+	struct ntb_msi_devres *dr = res;
+
+	dr->entry->write_msi_msg = NULL;
+	dr->entry->write_msi_msg_data = NULL;
+}
+
+static int ntbm_msi_setup_callback(struct ntb_dev *ntb, struct msi_desc *entry,
+				   struct ntb_msi_desc *msi_desc)
+{
+	struct ntb_msi_devres *dr;
+
+	dr = devres_alloc(ntbm_msi_callback_release,
+			  sizeof(struct ntb_msi_devres), GFP_KERNEL);
+	if (!dr)
+		return -ENOMEM;
+
+	dr->ntb = ntb;
+	dr->entry = entry;
+	dr->msi_desc = msi_desc;
+
+	devres_add(&ntb->dev, dr);
+
+	dr->entry->write_msi_msg = ntb_msi_write_msg;
+	dr->entry->write_msi_msg_data = dr;
+
+	return 0;
+}
+
+/**
+ * ntbm_msi_request_threaded_irq() - allocate an MSI interrupt
+ * @ntb:	NTB device context
+ * @handler:	Function to be called when the IRQ occurs
+ * @thread_fn:  Function to be called in a threaded interrupt context. NULL
+ *              for clients which handle everything in @handler
+ * @devname:    An ascii name for the claiming device, dev_name(dev) if NULL
+ * @dev_id:     A cookie passed back to the handler function
+ *
+ * This function assigns an interrupt handler to an unused
+ * MSI interrupt and returns the descriptor used to trigger
+ * it. The descriptor can then be sent to a peer to trigger
+ * the interrupt.
+ *
+ * The interrupt resource is managed with devres so it will
+ * be automatically freed when the NTB device is torn down.
+ *
+ * If an IRQ allocated with this function needs to be freed
+ * separately, ntbm_free_irq() must be used.
+ *
+ * Return: IRQ number assigned on success, otherwise a negative error number.
+ */
+int ntbm_msi_request_threaded_irq(struct ntb_dev *ntb, irq_handler_t handler,
+				  irq_handler_t thread_fn,
+				  const char *name, void *dev_id,
+				  struct ntb_msi_desc *msi_desc)
+{
+	struct msi_desc *entry;
+	struct irq_desc *desc;
+	int ret;
+
+	if (!ntb->msi)
+		return -EINVAL;
+
+	for_each_pci_msi_entry(entry, ntb->pdev) {
+		desc = irq_to_desc(entry->irq);
+		if (desc->action)
+			continue;
+
+		ret = devm_request_threaded_irq(&ntb->dev, entry->irq, handler,
+						thread_fn, 0, name, dev_id);
+		if (ret)
+			continue;
+
+		if (ntb_msi_set_desc(ntb, entry, msi_desc)) {
+			devm_free_irq(&ntb->dev, entry->irq, dev_id);
+			continue;
+		}
+
+		ret = ntbm_msi_setup_callback(ntb, entry, msi_desc);
+		if (ret) {
+			devm_free_irq(&ntb->dev, entry->irq, dev_id);
+			return ret;
+		}
+
+
+		return entry->irq;
+	}
+
+	return -ENODEV;
+}
+EXPORT_SYMBOL(ntbm_msi_request_threaded_irq);
+
+static int ntbm_msi_callback_match(struct device *dev, void *res, void *data)
+{
+	struct ntb_dev *ntb = dev_ntb(dev);
+	struct ntb_msi_devres *dr = res;
+
+	return dr->ntb == ntb && dr->entry == data;
+}
+
+/**
+ * ntbm_msi_free_irq() - free an interrupt
+ * @ntb:	NTB device context
+ * @irq:	Interrupt line to free
+ * @dev_id:	Device identity to free
+ *
+ * This function should be used to manually free IRQs allocated with
+ * ntbm_request_[threaded_]irq().
+ */
+void ntbm_msi_free_irq(struct ntb_dev *ntb, unsigned int irq, void *dev_id)
+{
+	struct msi_desc *entry = irq_get_msi_desc(irq);
+
+	entry->write_msi_msg = NULL;
+	entry->write_msi_msg_data = NULL;
+
+	WARN_ON(devres_destroy(&ntb->dev, ntbm_msi_callback_release,
+			       ntbm_msi_callback_match, entry));
+
+	devm_free_irq(&ntb->dev, irq, dev_id);
+}
+EXPORT_SYMBOL(ntbm_msi_free_irq);
+
+/**
+ * ntb_msi_peer_trigger() - Trigger an interrupt handler on a peer
+ * @ntb:	NTB device context
+ * @peer:	Peer index
+ * @desc:	MSI descriptor data which triggers the interrupt
+ *
+ * This function triggers an interrupt on a peer. It requires
+ * the descriptor structure to have been passed from that peer
+ * by some other means.
+ *
+ * Return: Zero on success, otherwise a negative error number.
+ */
+int ntb_msi_peer_trigger(struct ntb_dev *ntb, int peer,
+			 struct ntb_msi_desc *desc)
+{
+	int idx;
+
+	if (!ntb->msi)
+		return -EINVAL;
+
+	idx = desc->addr_offset / sizeof(*ntb->msi->peer_mws[peer]);
+
+	iowrite32(desc->data, &ntb->msi->peer_mws[peer][idx]);
+
+	return 0;
+}
+EXPORT_SYMBOL(ntb_msi_peer_trigger);
+
+/**
+ * ntb_msi_peer_addr() - Get the DMA address to trigger a peer's MSI interrupt
+ * @ntb:	NTB device context
+ * @peer:	Peer index
+ * @desc:	MSI descriptor data which triggers the interrupt
+ * @msi_addr:   Physical address to trigger the interrupt
+ *
+ * This function allows using DMA engines to trigger an interrupt
+ * (for example, trigger an interrupt to process the data after
+ * sending it). To trigger the interrupt, write @desc.data to the address
+ * returned in @msi_addr
+ *
+ * Return: Zero on success, otherwise a negative error number.
+ */
+int ntb_msi_peer_addr(struct ntb_dev *ntb, int peer,
+		      struct ntb_msi_desc *desc,
+		      phys_addr_t *msi_addr)
+{
+	int peer_widx = ntb_peer_mw_count(ntb) - 1 - peer;
+	phys_addr_t mw_phys_addr;
+	int ret;
+
+	ret = ntb_peer_mw_get_addr(ntb, peer_widx, &mw_phys_addr, NULL);
+	if (ret)
+		return ret;
+
+	if (msi_addr)
+		*msi_addr = mw_phys_addr + desc->addr_offset;
+
+	return 0;
+}
+EXPORT_SYMBOL(ntb_msi_peer_addr);
diff --git a/include/linux/ntb.h b/include/linux/ntb.h
index a14a43b17952..e732ad08d988 100644
--- a/include/linux/ntb.h
+++ b/include/linux/ntb.h
@@ -58,9 +58,11 @@
 
 #include <linux/completion.h>
 #include <linux/device.h>
+#include <linux/interrupt.h>
 
 struct ntb_client;
 struct ntb_dev;
+struct ntb_msi;
 struct pci_dev;
 
 /**
@@ -426,6 +428,10 @@ struct ntb_dev {
 	spinlock_t			ctx_lock;
 	/* block unregister until device is fully released */
 	struct completion		released;
+
+#ifdef CONFIG_NTB_MSI
+	struct ntb_msi *msi;
+#endif
 };
 #define dev_ntb(__dev) container_of((__dev), struct ntb_dev, dev)
 
@@ -1627,4 +1633,71 @@ static inline int ntb_peer_highest_mw_idx(struct ntb_dev *ntb, int pidx)
 	return ntb_mw_count(ntb, pidx) - ret - 1;
 }
 
+struct ntb_msi_desc {
+	u32 addr_offset;
+	u32 data;
+};
+
+#ifdef CONFIG_NTB_MSI
+
+int ntb_msi_init(struct ntb_dev *ntb, void (*desc_changed)(void *ctx));
+int ntb_msi_setup_mws(struct ntb_dev *ntb);
+void ntb_msi_clear_mws(struct ntb_dev *ntb);
+int ntbm_msi_request_threaded_irq(struct ntb_dev *ntb, irq_handler_t handler,
+				  irq_handler_t thread_fn,
+				  const char *name, void *dev_id,
+				  struct ntb_msi_desc *msi_desc);
+void ntbm_msi_free_irq(struct ntb_dev *ntb, unsigned int irq, void *dev_id);
+int ntb_msi_peer_trigger(struct ntb_dev *ntb, int peer,
+			 struct ntb_msi_desc *desc);
+int ntb_msi_peer_addr(struct ntb_dev *ntb, int peer,
+		      struct ntb_msi_desc *desc,
+		      phys_addr_t *msi_addr);
+
+#else /* not CONFIG_NTB_MSI */
+
+static inline int ntb_msi_init(struct ntb_dev *ntb,
+			       void (*desc_changed)(void *ctx))
+{
+	return -EOPNOTSUPP;
+}
+static inline int ntb_msi_setup_mws(struct ntb_dev *ntb)
+{
+	return -EOPNOTSUPP;
+}
+static inline void ntb_msi_clear_mws(struct ntb_dev *ntb) {}
+static inline int ntbm_msi_request_threaded_irq(struct ntb_dev *ntb,
+						irq_handler_t handler,
+						irq_handler_t thread_fn,
+						const char *name, void *dev_id,
+						struct ntb_msi_desc *msi_desc)
+{
+	return -EOPNOTSUPP;
+}
+static inline void ntbm_msi_free_irq(struct ntb_dev *ntb, unsigned int irq,
+				     void *dev_id) {}
+static inline int ntb_msi_peer_trigger(struct ntb_dev *ntb, int peer,
+				       struct ntb_msi_desc *desc)
+{
+	return -EOPNOTSUPP;
+}
+static inline int ntb_msi_peer_addr(struct ntb_dev *ntb, int peer,
+				    struct ntb_msi_desc *desc,
+				    phys_addr_t *msi_addr)
+{
+	return -EOPNOTSUPP;
+
+}
+
+#endif /* CONFIG_NTB_MSI */
+
+static inline int ntbm_msi_request_irq(struct ntb_dev *ntb,
+				       irq_handler_t handler,
+				       const char *name, void *dev_id,
+				       struct ntb_msi_desc *msi_desc)
+{
+	return ntbm_msi_request_threaded_irq(ntb, handler, NULL, name,
+					     dev_id, msi_desc);
+}
+
 #endif
