[PATCH v12 00/11] KVM PCIe/MSI passthrough on ARM/ARM64: kernel part 2/3: msi changes

@@ -400,5 +400,6 @@ struct msi_domain_info *msi_get_domain_info(struct irq_domain *domain)
 {
 	return (struct msi_domain_info *)domain->host_data;
 }
+EXPORT_SYMBOL_GPL(msi_get_domain_info);
 
 #endif /* CONFIG_GENERIC_MSI_IRQ_DOMAIN */

@@ -29,6 +29,8 @@
 #include <linux/of_platform.h>
 #include <linux/percpu.h>
 #include <linux/slab.h>
+#include <linux/iommu.h>
+#include <linux/msi-doorbell.h>
 
 #include <linux/irqchip.h>
 #include <linux/irqchip/arm-gic-v3.h>

@@ -71,19 +73,20 @@ struct its_baser {
  * list of devices writing to it.
  */
 struct its_node {
-	raw_spinlock_t		lock;
-	struct list_head	entry;
-	void __iomem		*base;
-	unsigned long		phys_base;
-	struct its_cmd_block	*cmd_base;
-	struct its_cmd_block	*cmd_write;
-	struct its_baser	tables[GITS_BASER_NR_REGS];
-	struct its_collection	*collections;
-	struct list_head	its_device_list;
-	u64			flags;
-	u32			ite_size;
-	u32			device_ids;
-	int			numa_node;
+	raw_spinlock_t			lock;
+	struct list_head		entry;
+	void __iomem			*base;
+	unsigned long			phys_base;
+	struct its_cmd_block		*cmd_base;
+	struct its_cmd_block		*cmd_write;
+	struct its_baser		tables[GITS_BASER_NR_REGS];
+	struct its_collection		*collections;
+	struct list_head		its_device_list;
+	u64				flags;
+	u32				ite_size;
+	u32				device_ids;
+	int				numa_node;
+	struct msi_doorbell_info	*doorbell_info;
 };
 
 #define ITS_ITT_ALIGN		SZ_256

@@ -656,13 +659,24 @@ static void its_irq_compose_msi_msg(struct irq_data *d, struct msi_msg *msg)
 	msg->data		= its_get_event_id(d);
 }
 
+static struct msi_doorbell_info *
+its_irq_get_msi_doorbell_info(struct irq_data *d)
+{
+	struct its_device *its_dev = irq_data_get_irq_chip_data(d);
+	struct its_node *its = its_dev->its;
+
+	return its->doorbell_info;
+}
+
+
 static struct irq_chip its_irq_chip = {
-	.name			= "ITS",
-	.irq_mask		= its_mask_irq,
-	.irq_unmask		= its_unmask_irq,
-	.irq_eoi		= irq_chip_eoi_parent,
-	.irq_set_affinity	= its_set_affinity,
-	.irq_compose_msi_msg	= its_irq_compose_msi_msg,
+	.name				= "ITS",
+	.irq_mask			= its_mask_irq,
+	.irq_unmask			= its_unmask_irq,
+	.irq_eoi			= irq_chip_eoi_parent,
+	.irq_set_affinity		= its_set_affinity,
+	.irq_compose_msi_msg		= its_irq_compose_msi_msg,
+	.irq_get_msi_doorbell_info	= its_irq_get_msi_doorbell_info,
 };
 
 /*

@@ -1607,6 +1621,7 @@ static int __init its_probe(struct device_node *node,
 
 	if (of_property_read_bool(node, "msi-controller")) {
 		struct msi_domain_info *info;
+		phys_addr_t translater;
 
 		info = kzalloc(sizeof(*info), GFP_KERNEL);
 		if (!info) {

@@ -1614,10 +1629,24 @@ static int __init its_probe(struct device_node *node,
 			goto out_free_tables;
 		}
 
+		translater = its->phys_base + GITS_TRANSLATER;
+		its->doorbell_info =
+			msi_doorbell_register_global(translater, sizeof(u32),
+						     IOMMU_WRITE | IOMMU_MMIO,
+						     true);
+
+		if (!its->doorbell_info)  {
+			err = -ENOMEM;
+			kfree(info);
+			goto out_free_tables;
+		}
+
+
 		inner_domain = irq_domain_add_tree(node, &its_domain_ops, its);
 		if (!inner_domain) {
 			err = -ENOMEM;
 			kfree(info);
+			msi_doorbell_unregister_global(its->doorbell_info);
 			goto out_free_tables;
 		}
 

@@ -14,6 +14,9 @@
 #include <linux/irq.h>
 #include <linux/irqdomain.h>
 #include <linux/msi.h>
+#include <linux/msi-iommu.h>
+#include <linux/iommu.h>
+#include <linux/msi-doorbell.h>
 
 /* Temparory solution for building, will be removed later */
 #include <linux/pci.h>

@@ -322,6 +325,131 @@ int msi_domain_populate_irqs(struct irq_domain *domain, struct device *dev,
 }
 
 /**
+ * msi_get_doorbell_info - return the MSI doorbell descriptor corresponding
+ * to an irq data
+ * @data: irq data handle
+ *
+ * Return: the doorbell descriptor pointer if any, NULL if none, an ERR_PTR
+ * otherwise
+ */
+static struct msi_doorbell_info *msi_get_doorbell_info(struct irq_data *data)
+{
+	struct irq_chip *chip;
+
+	while (data) {
+		chip = irq_data_get_irq_chip(data);
+		if (chip->irq_get_msi_doorbell_info)
+			break;
+		data = data->parent_data;
+	}
+
+	if (!data)
+		return NULL;
+
+	return chip->irq_get_msi_doorbell_info(data);
+}
+
+/**
+ * msi_map_global_doorbell - iommu map/unmap the global doorbell physical
+ * address
+ * @domain: iommu domain the mapping is associated to
+ * @dbi: doorbell descriptor
+ * @map: true if map operation, false if unmap operation
+ *
+ * Return: 0 on success or an error code
+ */
+static int msi_map_global_doorbell(struct iommu_domain *domain,
+			       const struct msi_doorbell_info *dbi, bool map)
+{
+	dma_addr_t iova;
+	int ret = 0;
+
+	if (map)
+		ret = iommu_msi_get_doorbell_iova(domain, dbi->global_doorbell,
+						  dbi->size, dbi->prot, &iova);
+	else
+		iommu_msi_put_doorbell_iova(domain, dbi->global_doorbell);
+	return ret;
+}
+
+/**
+ * msi_map_percpu_doorbell - iommu map/unmap the percpu doorbell physical
+ * addresses
+ * @domain: iommu domain the mapping is associated to
+ * @dbi: doorbell descriptor
+ * @map: true if map operation, false if unmap operation
+ *
+ * Return: 0 on success or an error code
+ */
+static int msi_map_percpu_doorbell(struct iommu_domain *domain,
+			       const struct msi_doorbell_info *dbi, bool map)
+{
+	int cpu, ret;
+
+	for_each_possible_cpu(cpu) {
+		phys_addr_t __percpu *db_addr;
+		dma_addr_t iova;
+
+		db_addr = per_cpu_ptr(dbi->percpu_doorbells, cpu);
+
+		if (map) {
+			ret = iommu_msi_get_doorbell_iova(domain, *db_addr,
+							  dbi->size, dbi->prot,
+							  &iova);
+			if (ret)
+				return ret;
+		} else {
+			iommu_msi_put_doorbell_iova(domain, *db_addr);
+		}
+	}
+	return 0;
+}
+
+/**
+ * msi_handle_doorbell_mappings - IOMMU map/unmap any MSI doorbell associated
+ * to the irq data handle
+ * @data: irq data handle
+ * @map: true if map operation, false if unmap operation
+ *
+ * In case the irq data corresponds to an MSI sent by a device in front of
+ * an IOMMU and this latter does not bypass MSI transactions,
+ * traverse the irq domain hierarchy to retrieve the MSI doorbells and
+ * iommu_map/unmap them according to @map boolean.
+ *
+ * Return 0 on success or if no action is required, or an error code
+ */
+static int msi_handle_doorbell_mappings(struct irq_data *data, bool map)
+{
+	const struct msi_doorbell_info *dbi;
+	struct iommu_domain *domain;
+	struct device *dev;
+
+	/* Is the MSI address translated by an IOMMU? */
+	dev = msi_desc_to_dev(irq_data_get_msi_desc(data));
+	domain = iommu_msi_domain(dev);
+	if (!domain)
+		return 0;
+
+	/**
+	 * Do we find a doorbell to IOMMU map?
+	 * If we don't either the doorbell registration failed, or
+	 * the actual MSI controller did not register its doorbell:
+	 * either the MSI controller is behind the IOMMU and the MSI
+	 * controller should have registered its doorbell; or the MSI
+	 * controller is inbetween the device and the IOMMU. We currently
+	 * do not support this case.
+	 */
+	dbi = msi_get_doorbell_info(data);
+	if (!dbi)
+		return -ENODEV;
+
+	if (dbi->doorbell_is_percpu)
+		return msi_map_percpu_doorbell(domain, dbi, map);
+	else
+		return msi_map_global_doorbell(domain, dbi, map);
+}
+
+/**
  * msi_domain_alloc_irqs - Allocate interrupts from a MSI interrupt domain
  * @domain:	The domain to allocate from
  * @dev:	Pointer to device struct of the device for which the interrupts

@@ -354,18 +482,23 @@ int msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
 					       dev_to_node(dev), &arg, false);
 		if (virq < 0) {
 			ret = -ENOSPC;
-			if (ops->handle_error)
-				ret = ops->handle_error(domain, desc, ret);
-			if (ops->msi_finish)
-				ops->msi_finish(&arg, ret);
-			return ret;
+			goto error;
 		}
 
 		desc->flags |= MSI_DESC_FLAG_ALLOCATED;
-		desc->flags |= MSI_DESC_FLAG_FUNCTIONAL;
 
 		for (i = 0; i < desc->nvec_used; i++)
 			irq_set_msi_desc_off(virq, i, desc);
+
+		for (i = 0; i < desc->nvec_used; i++) {
+			struct irq_data *d = irq_get_irq_data(virq + i);
+
+			ret = msi_handle_doorbell_mappings(d, true);
+			if (ret)
+				goto error;
+		}
+
+		desc->flags |= MSI_DESC_FLAG_FUNCTIONAL;
 	}
 
 	if (ops->msi_finish)

@@ -380,6 +513,12 @@ int msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
 	}
 
 	return 0;
+error:
+	if (ops->handle_error)
+		ret = ops->handle_error(domain, desc, ret);
+	if (ops->msi_finish)
+		ops->msi_finish(&arg, ret);
+	return ret;
 }
 
 /**

@@ -399,6 +538,9 @@ void msi_domain_free_irqs(struct irq_domain *domain, struct device *dev)
 		 * entry. If that's the case, don't do anything.
 		 */
 		if (desc->flags & MSI_DESC_FLAG_ALLOCATED) {
+			struct irq_data *d = irq_get_irq_data(desc->irq);
+
+			msi_handle_doorbell_mappings(d, false);
 			irq_domain_free_irqs(desc->irq, desc->nvec_used);
 			desc->irq = 0;
 			desc->flags &= ~MSI_DESC_FLAG_ALLOCATED;

@@ -793,7 +793,7 @@ out_avail:
 		int avail = 0;
 
 		for_each_pci_msi_entry(entry, dev) {
-			if (entry->irq != 0)
+			if (entry->flags & MSI_DESC_FLAG_FUNCTIONAL)
 				avail++;
 		}
 		if (avail != 0)

@@ -47,6 +47,7 @@ struct fsl_mc_msi_desc {
  * @nvec_used:	The number of vectors used
  * @dev:	Pointer to the device which uses this descriptor
  * @msg:	The last set MSI message cached for reuse
+ * @flags:	flags to describe the MSI descriptor status or features
  *
  * @masked:	[PCI MSI/X] Mask bits
  * @is_msix:	[PCI MSI/X] True if MSI-X

@@ -67,6 +68,7 @@ struct msi_desc {
 	unsigned int			nvec_used;
 	struct device			*dev;
 	struct msi_msg			msg;
+	u32						flags;
 
 	union {
 		/* PCI MSI/X specific data */

@@ -99,6 +101,18 @@ struct msi_desc {
 	};
 };
 
+/* Flags for msi_desc */
+enum {
+	/* the base IRQ is allocated */
+	MSI_DESC_FLAG_ALLOCATED	=	(1 << 0),
+	/**
+	 * the MSI is functional; in some cases the fact the base IRQ is
+	 * allocated is not sufficient for the MSIs to be functional: for
+	 * example the MSI doorbell(s) may need to be IOMMU mapped.
+	 */
+	MSI_DESC_FLAG_FUNCTIONAL =	(1 << 1),
+};
+
 /* Helpers to hide struct msi_desc implementation details */
 #define msi_desc_to_dev(desc)		((desc)->dev)
 #define dev_to_msi_list(dev)		(&(dev)->msi_list)

@@ -361,6 +361,9 @@ int msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
 			return ret;
 		}
 
+		desc->flags |= MSI_DESC_FLAG_ALLOCATED;
+		desc->flags |= MSI_DESC_FLAG_FUNCTIONAL;
+
 		for (i = 0; i < desc->nvec_used; i++)
 			irq_set_msi_desc_off(virq, i, desc);
 	}

@@ -395,9 +398,11 @@ void msi_domain_free_irqs(struct irq_domain *domain, struct device *dev)
 		 * enough that there is no IRQ associated to this
 		 * entry. If that's the case, don't do anything.
 		 */
-		if (desc->irq) {
+		if (desc->flags & MSI_DESC_FLAG_ALLOCATED) {
 			irq_domain_free_irqs(desc->irq, desc->nvec_used);
 			desc->irq = 0;
+			desc->flags &= ~MSI_DESC_FLAG_ALLOCATED;
+			desc->flags &= ~MSI_DESC_FLAG_FUNCTIONAL;
 		}
 	}
 }

@@ -24,6 +24,8 @@
 #include <linux/of_pci.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
+#include <linux/iommu.h>
+#include <linux/msi-doorbell.h>
 
 /*
 * MSI_TYPER:

@@ -68,6 +70,7 @@ struct v2m_data {
 	u32 spi_offset;		/* offset to be subtracted from SPI number */
 	unsigned long *bm;	/* MSI vector bitmap */
 	u32 flags;		/* v2m flags for specific implementation */
+	struct msi_doorbell_info *doorbell_info; /* MSI doorbell */
 };
 
 static void gicv2m_mask_msi_irq(struct irq_data *d)

@@ -109,13 +112,22 @@ static void gicv2m_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 		msg->data -= v2m->spi_offset;
 }
 
+static struct msi_doorbell_info *
+gicv2m_irq_get_msi_doorbell_info(struct irq_data *data)
+{
+	struct v2m_data *v2m = irq_data_get_irq_chip_data(data);
+
+	return v2m->doorbell_info;
+}
+
 static struct irq_chip gicv2m_irq_chip = {
-	.name			= "GICv2m",
-	.irq_mask		= irq_chip_mask_parent,
-	.irq_unmask		= irq_chip_unmask_parent,
-	.irq_eoi		= irq_chip_eoi_parent,
-	.irq_set_affinity	= irq_chip_set_affinity_parent,
-	.irq_compose_msi_msg	= gicv2m_compose_msi_msg,
+	.name				= "GICv2m",
+	.irq_mask			= irq_chip_mask_parent,
+	.irq_unmask			= irq_chip_unmask_parent,
+	.irq_eoi			= irq_chip_eoi_parent,
+	.irq_set_affinity		= irq_chip_set_affinity_parent,
+	.irq_compose_msi_msg		= gicv2m_compose_msi_msg,
+	.irq_get_msi_doorbell_info	= gicv2m_irq_get_msi_doorbell_info,
 };
 
 static int gicv2m_irq_gic_domain_alloc(struct irq_domain *domain,

@@ -366,12 +378,21 @@ static int __init gicv2m_init_one(struct fwnode_handle *fwnode,
 		goto err_iounmap;
 	}
 
+	v2m->doorbell_info =
+		msi_doorbell_register_global(v2m->res.start, sizeof(u32),
+					     IOMMU_WRITE | IOMMU_MMIO, false);
+	if (!v2m->doorbell_info) {
+		ret = -ENOMEM;
+		goto err_free_bm;
+	}
+
 	list_add_tail(&v2m->entry, &v2m_nodes);
 
 	pr_info("range%pR, SPI[%d:%d]\n", res,
 		v2m->spi_start, (v2m->spi_start + v2m->nr_spis - 1));
 	return 0;
-
+err_free_bm:
+	kfree(v2m->bm);
 err_iounmap:
 	iounmap(v2m->base);
 err_free_v2m:

@@ -63,10 +63,18 @@ static int msi_compose(struct irq_data *irq_data,
 {
 	int ret = 0;
 
-	if (erase)
+	if (erase) {
 		memset(msg, 0, sizeof(*msg));
-	else
+	} else {
+		struct device *dev;
+
 		ret = irq_chip_compose_msi_msg(irq_data, msg);
+		if (ret)
+			return ret;
+
+		dev = msi_desc_to_dev(irq_data_get_msi_desc(irq_data));
+		ret = iommu_msi_msg_pa_to_va(dev, msg);
+	}
 
 	return ret;
 }

@@ -47,6 +47,14 @@ void msi_doorbell_unregister_global(struct msi_doorbell_info *db);
  */
 int msi_doorbell_calc_pages(unsigned int order);
 
+/**
+ * msi_doorbell_safe - return whether all registered doorbells are safe
+ *
+ * Safe doorbells are those which implement irq remapping
+ * Return: true if all doorbells are safe, false otherwise
+ */
+bool msi_doorbell_safe(void);
+
 #else
 
 static inline struct msi_doorbell_info *

@@ -64,6 +72,11 @@ static inline int msi_doorbell_calc_pages(unsigned int order)
 	return 0;
 }
 
+static inline bool
+msi_doorbell_safe(void)
+{
+	return true;
+}
 #endif /* CONFIG_MSI_DOORBELL */
 
 #endif

@@ -130,3 +130,9 @@ int msi_doorbell_calc_pages(unsigned int order)
 	return ret;
 }
 EXPORT_SYMBOL_GPL(msi_doorbell_calc_pages);
+
+bool msi_doorbell_safe(void)
+{
+	return !nb_unsafe_doorbells;
+}
+EXPORT_SYMBOL_GPL(msi_doorbell_safe);

@@ -55,6 +55,19 @@ static inline void irq_chip_write_msi_msg(struct irq_data *data,
 	data->chip->irq_write_msi_msg(data, msg);
 }
 
+static int msi_compose(struct irq_data *irq_data,
+		       struct msi_msg *msg, bool erase)
+{
+	int ret = 0;
+
+	if (erase)
+		memset(msg, 0, sizeof(*msg));
+	else
+		ret = irq_chip_compose_msi_msg(irq_data, msg);
+
+	return ret;
+}
+
 /**
  * msi_domain_set_affinity - Generic affinity setter function for MSI domains
  * @irq_data:	The irq data associated to the interrupt

@@ -73,7 +86,7 @@ int msi_domain_set_affinity(struct irq_data *irq_data,
 
 	ret = parent->chip->irq_set_affinity(parent, mask, force);
 	if (ret >= 0 && ret != IRQ_SET_MASK_OK_DONE) {
-		BUG_ON(irq_chip_compose_msi_msg(irq_data, &msg));
+		BUG_ON(msi_compose(irq_data, &msg, false));
 		irq_chip_write_msi_msg(irq_data, &msg);
 	}
 

@@ -85,7 +98,7 @@ static void msi_domain_activate(struct irq_domain *domain,
 {
 	struct msi_msg msg;
 
-	BUG_ON(irq_chip_compose_msi_msg(irq_data, &msg));
+	BUG_ON(msi_compose(irq_data, &msg, false));
 	irq_chip_write_msi_msg(irq_data, &msg);
 }
 

@@ -94,7 +107,7 @@ static void msi_domain_deactivate(struct irq_domain *domain,
 {
 	struct msi_msg msg;
 
-	memset(&msg, 0, sizeof(msg));
+	msi_compose(irq_data, &msg, true);
 	irq_chip_write_msi_msg(irq_data, &msg);
 }
 

@@ -313,6 +313,26 @@ static inline irq_hw_number_t irqd_to_hwirq(struct irq_data *d)
 }
 
 /**
+ * struct msi_doorbell_info - MSI doorbell region descriptor
+ * @percpu_doorbells: per cpu doorbell base address
+ * @global_doorbell: base address of the doorbell
+ * @doorbell_is_percpu: is the doorbell per cpu or global?
+ * @irq_remapping: is irq_remapping implemented?
+ * @size: size of the doorbell
+ * @prot: iommu protection flag
+ */
+struct msi_doorbell_info {
+	union {
+		phys_addr_t __percpu	*percpu_doorbells;
+		phys_addr_t		global_doorbell;
+	};
+	bool	doorbell_is_percpu;
+	bool	irq_remapping;
+	size_t	size;
+	int	prot;
+};
+
+/**
  * struct irq_chip - hardware interrupt chip descriptor
  *
  * @name:		name for /proc/interrupts

@@ -349,6 +369,7 @@ static inline irq_hw_number_t irqd_to_hwirq(struct irq_data *d)
  * @irq_get_irqchip_state:	return the internal state of an interrupt
  * @irq_set_irqchip_state:	set the internal state of a interrupt
  * @irq_set_vcpu_affinity:	optional to target a vCPU in a virtual machine
+ * @irq_get_msi_doorbell_info:	return the MSI doorbell info
  * @ipi_send_single:	send a single IPI to destination cpus
  * @ipi_send_mask:	send an IPI to destination cpus in cpumask
  * @flags:		chip specific flags

@@ -394,7 +415,7 @@ struct irq_chip {
 	int		(*irq_set_irqchip_state)(struct irq_data *data, enum irqchip_irq_state which, bool state);
 
 	int		(*irq_set_vcpu_affinity)(struct irq_data *data, void *vcpu_info);
-
+	struct msi_doorbell_info *(*irq_get_msi_doorbell_info)(struct irq_data *data);
 	void		(*ipi_send_single)(struct irq_data *data, unsigned int cpu);
 	void		(*ipi_send_mask)(struct irq_data *data, const struct cpumask *dest);
 

@@ -38,6 +38,15 @@ msi_doorbell_register_global(phys_addr_t base, size_t size,
  */
 void msi_doorbell_unregister_global(struct msi_doorbell_info *db);
 
+/**
+ * msi_doorbell_calc_pages - compute the number of pages
+ * requested to map all the registered doorbells
+ * @order: iommu page order
+ *
+ * Return: the number of requested pages
+ */
+int msi_doorbell_calc_pages(unsigned int order);
+
 #else
 
 static inline struct msi_doorbell_info *

@@ -50,6 +59,11 @@ msi_doorbell_register_global(phys_addr_t base, size_t size,
 static inline void
 msi_doorbell_unregister_global(struct msi_doorbell_info *db) {}
 
+static inline int msi_doorbell_calc_pages(unsigned int order)
+{
+	return 0;
+}
+
 #endif /* CONFIG_MSI_DOORBELL */
 
 #endif

@@ -66,3 +66,67 @@ void msi_doorbell_unregister_global(struct msi_doorbell_info *dbinfo)
 	kfree(db);
 }
 EXPORT_SYMBOL_GPL(msi_doorbell_unregister_global);
+
+/**
+ * calc_region_reqs - compute the number of pages requested to map a region
+ *
+ * @addr: physical base address of the region
+ * @size: size of the region
+ * @order: the page order
+ *
+ * Return: the number of requested pages to map this region
+ */
+static int calc_region_reqs(phys_addr_t addr, size_t size, unsigned int order)
+{
+	phys_addr_t offset, granule;
+	unsigned int nb_pages;
+
+	granule = (uint64_t)(1 << order);
+	offset = addr & (granule - 1);
+	size = ALIGN(size + offset, granule);
+	nb_pages = size >> order;
+
+	return nb_pages;
+}
+
+/**
+ * calc_dbinfo_reqs - compute the number of pages requested to map a given
+ * MSI doorbell
+ *
+ * @dbi: doorbell info descriptor
+ * @order: page order
+ *
+ * Return: the number of requested pages to map this doorbell
+ */
+static int calc_dbinfo_reqs(struct msi_doorbell_info *dbi, unsigned int order)
+{
+	int ret = 0;
+
+	if (!dbi->doorbell_is_percpu) {
+		ret = calc_region_reqs(dbi->global_doorbell, dbi->size, order);
+	} else {
+		phys_addr_t __percpu *pbase;
+		int cpu;
+
+		for_each_possible_cpu(cpu) {
+			pbase = per_cpu_ptr(dbi->percpu_doorbells, cpu);
+			ret += calc_region_reqs(*pbase, dbi->size, order);
+		}
+	}
+	return ret;
+}
+
+int msi_doorbell_calc_pages(unsigned int order)
+{
+	struct msi_doorbell *db;
+	int ret = 0;
+
+	mutex_lock(&msi_doorbell_mutex);
+	list_for_each_entry(db, &msi_doorbell_list, next)
+		ret += calc_dbinfo_reqs(&db->info, order);
+
+	mutex_unlock(&msi_doorbell_mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(msi_doorbell_calc_pages);

@@ -78,6 +78,7 @@ config IOMMU_DMA
 config IOMMU_MSI
 	bool
 	select IOMMU_DMA
+	select MSI_DOORBELL
 
 config FSL_PAMU
 	bool "Freescale IOMMU support"

@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2016 Eric Auger
+ *
+ * Eric Auger <eric.auger@linaro.org>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2.  This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#ifndef _LINUX_MSI_DOORBELL_H
+#define _LINUX_MSI_DOORBELL_H
+
+#include <linux/irq.h>
+
+#ifdef CONFIG_MSI_DOORBELL
+
+/**
+ * msi_doorbell_register_global - allocate and register a global doorbell
+ * @base: physical base address of the global doorbell
+ * @size: size of the global doorbell
+ * @prot: protection/memory attributes
+ * @irq_remapping: is irq_remapping implemented for this doorbell
+ *
+ * Return: the newly allocated doorbell info handle or NULL if allocation
+ * failed
+ */
+struct msi_doorbell_info *
+msi_doorbell_register_global(phys_addr_t base, size_t size,
+			     int prot, bool irq_remapping);
+
+/**
+ * msi_doorbell_unregister_global - unregister a global doorbell
+ * @db: doorbell info to unregister
+ *
+ * remove the doorbell descriptor from the list of registered doorbells
+ * and deallocates it
+ */
+void msi_doorbell_unregister_global(struct msi_doorbell_info *db);
+
+#else
+
+static inline struct msi_doorbell_info *
+msi_doorbell_register_global(phys_addr_t base, size_t size,
+			     int prot, bool irq_remapping)
+{
+	return NULL;
+}
+
+static inline void
+msi_doorbell_unregister_global(struct msi_doorbell_info *db) {}
+
+#endif /* CONFIG_MSI_DOORBELL */
+
+#endif

@@ -72,6 +72,10 @@ config GENERIC_IRQ_IPI
 config GENERIC_MSI_IRQ
 	bool
 
+# MSI doorbell support (for doorbell IOMMU mapping)
+config MSI_DOORBELL
+	bool
+
 # Generic MSI hierarchical interrupt domain support
 config GENERIC_MSI_IRQ_DOMAIN
 	bool

@@ -9,3 +9,4 @@ obj-$(CONFIG_GENERIC_IRQ_MIGRATION) += cpuhotplug.o
 obj-$(CONFIG_PM_SLEEP) += pm.o
 obj-$(CONFIG_GENERIC_MSI_IRQ) += msi.o
 obj-$(CONFIG_GENERIC_IRQ_IPI) += ipi.o
+obj-$(CONFIG_MSI_DOORBELL) += msi-doorbell.o

@@ -0,0 +1,68 @@
+/*
+ * linux/kernel/irq/msi-doorbell.c
+ *
+ * Copyright (C) 2016 Linaro
+ * Author: Eric Auger <eric.auger@linaro.org>
+ *
+ * This file is licensed under GPLv2.
+ *
+ * This file contains common code to manage MSI doorbells likely
+ * to be iommu mapped. Typically meaningful on ARM.
+ */
+
+#include <linux/slab.h>
+#include <linux/irq.h>
+#include <linux/msi-doorbell.h>
+
+struct msi_doorbell {
+	struct msi_doorbell_info	info;
+	struct list_head		next;
+};
+
+/* list of registered MSI doorbells */
+static LIST_HEAD(msi_doorbell_list);
+
+/* counts the number of unsafe registered doorbells */
+static uint nb_unsafe_doorbells;
+
+/* protects the list and nb__unsafe_doorbells */
+static DEFINE_MUTEX(msi_doorbell_mutex);
+
+struct msi_doorbell_info *
+msi_doorbell_register_global(phys_addr_t base, size_t size,
+			     int prot, bool irq_remapping)
+{
+	struct msi_doorbell *db;
+
+	db = kzalloc(sizeof(*db), GFP_KERNEL);
+	if (!db)
+		return NULL;
+
+	db->info.global_doorbell = base;
+	db->info.size = size;
+	db->info.prot = prot;
+	db->info.irq_remapping = irq_remapping;
+
+	mutex_lock(&msi_doorbell_mutex);
+	list_add(&db->next, &msi_doorbell_list);
+	if (!db->info.irq_remapping)
+		nb_unsafe_doorbells++;
+	mutex_unlock(&msi_doorbell_mutex);
+	return &db->info;
+}
+EXPORT_SYMBOL_GPL(msi_doorbell_register_global);
+
+void msi_doorbell_unregister_global(struct msi_doorbell_info *dbinfo)
+{
+	struct msi_doorbell *db;
+
+	db = container_of(dbinfo, struct msi_doorbell, info);
+
+	mutex_lock(&msi_doorbell_mutex);
+	list_del(&db->next);
+	if (!db->info.irq_remapping)
+		nb_unsafe_doorbells--;
+	mutex_unlock(&msi_doorbell_mutex);
+	kfree(db);
+}
+EXPORT_SYMBOL_GPL(msi_doorbell_unregister_global);