ocxl: Add AFU interrupt support

Add user APIs through ioctl to allocate, free, and be notified of an
AFU interrupt.

For opencapi, an AFU can trigger an interrupt on the host by sending a
specific command targeting a 64-bit object handle. On POWER9, this is
implemented by mapping a special page in the address space of a
process and a write to that page will trigger an interrupt.
Signed-off-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/pnv-ocxl.h

@@ -30,4 +30,7 @@ extern int pnv_ocxl_spa_setup(struct pci_dev *dev, void *spa_mem, int PE_mask,
 extern void pnv_ocxl_spa_release(void *platform_data);
 extern int pnv_ocxl_spa_remove_pe(void *platform_data, int pe_handle);
 
+extern int pnv_ocxl_alloc_xive_irq(u32 *irq, u64 *trigger_addr);
+extern void pnv_ocxl_free_xive_irq(u32 irq);
+
 #endif /* _ASM_PNV_OCXL_H */

arch/powerpc/platforms/powernv/ocxl.c

@@ -2,6 +2,7 @@
 // Copyright 2017 IBM Corp.
 #include <asm/pnv-ocxl.h>
 #include <asm/opal.h>
+#include <asm/xive.h>
 #include <misc/ocxl-config.h>
 #include "pci.h"
 
@@ -483,3 +484,32 @@ int pnv_ocxl_spa_remove_pe(void *platform_data, int pe_handle)
 	return rc;
 }
 EXPORT_SYMBOL_GPL(pnv_ocxl_spa_remove_pe);
+
+int pnv_ocxl_alloc_xive_irq(u32 *irq, u64 *trigger_addr)
+{
+	__be64 flags, trigger_page;
+	s64 rc;
+	u32 hwirq;
+
+	hwirq = xive_native_alloc_irq();
+	if (!hwirq)
+		return -ENOENT;
+
+	rc = opal_xive_get_irq_info(hwirq, &flags, NULL, &trigger_page, NULL,
+				NULL);
+	if (rc || !trigger_page) {
+		xive_native_free_irq(hwirq);
+		return -ENOENT;
+	}
+	*irq = hwirq;
+	*trigger_addr = be64_to_cpu(trigger_page);
+	return 0;
+
+}
+EXPORT_SYMBOL_GPL(pnv_ocxl_alloc_xive_irq);
+
+void pnv_ocxl_free_xive_irq(u32 irq)
+{
+	xive_native_free_irq(irq);
+}
+EXPORT_SYMBOL_GPL(pnv_ocxl_free_xive_irq);

drivers/misc/ocxl/afu_irq.c

+// SPDX-License-Identifier: GPL-2.0+
+// Copyright 2017 IBM Corp.
+#include <linux/interrupt.h>
+#include <linux/eventfd.h>
+#include <asm/pnv-ocxl.h>
+#include "ocxl_internal.h"
+
+struct afu_irq {
+	int id;
+	int hw_irq;
+	unsigned int virq;
+	char *name;
+	u64 trigger_page;
+	struct eventfd_ctx *ev_ctx;
+};
+
+static int irq_offset_to_id(struct ocxl_context *ctx, u64 offset)
+{
+	return (offset - ctx->afu->irq_base_offset) >> PAGE_SHIFT;
+}
+
+static u64 irq_id_to_offset(struct ocxl_context *ctx, int id)
+{
+	return ctx->afu->irq_base_offset + (id << PAGE_SHIFT);
+}
+
+static irqreturn_t afu_irq_handler(int virq, void *data)
+{
+	struct afu_irq *irq = (struct afu_irq *) data;
+
+	if (irq->ev_ctx)
+		eventfd_signal(irq->ev_ctx, 1);
+	return IRQ_HANDLED;
+}
+
+static int setup_afu_irq(struct ocxl_context *ctx, struct afu_irq *irq)
+{
+	int rc;
+
+	irq->virq = irq_create_mapping(NULL, irq->hw_irq);
+	if (!irq->virq) {
+		pr_err("irq_create_mapping failed\n");
+		return -ENOMEM;
+	}
+	pr_debug("hw_irq %d mapped to virq %u\n", irq->hw_irq, irq->virq);
+
+	irq->name = kasprintf(GFP_KERNEL, "ocxl-afu-%u", irq->virq);
+	if (!irq->name) {
+		irq_dispose_mapping(irq->virq);
+		return -ENOMEM;
+	}
+
+	rc = request_irq(irq->virq, afu_irq_handler, 0, irq->name, irq);
+	if (rc) {
+		kfree(irq->name);
+		irq->name = NULL;
+		irq_dispose_mapping(irq->virq);
+		pr_err("request_irq failed: %d\n", rc);
+		return rc;
+	}
+	return 0;
+}
+
+static void release_afu_irq(struct afu_irq *irq)
+{
+	free_irq(irq->virq, irq);
+	irq_dispose_mapping(irq->virq);
+	kfree(irq->name);
+}
+
+int ocxl_afu_irq_alloc(struct ocxl_context *ctx, u64 *irq_offset)
+{
+	struct afu_irq *irq;
+	int rc;
+
+	irq = kzalloc(sizeof(struct afu_irq), GFP_KERNEL);
+	if (!irq)
+		return -ENOMEM;
+
+	/*
+	 * We limit the number of afu irqs per context and per link to
+	 * avoid a single process or user depleting the pool of IPIs
+	 */
+
+	mutex_lock(&ctx->irq_lock);
+
+	irq->id = idr_alloc(&ctx->irq_idr, irq, 0, MAX_IRQ_PER_CONTEXT,
+			GFP_KERNEL);
+	if (irq->id < 0) {
+		rc = -ENOSPC;
+		goto err_unlock;
+	}
+
+	rc = ocxl_link_irq_alloc(ctx->afu->fn->link, &irq->hw_irq,
+				&irq->trigger_page);
+	if (rc)
+		goto err_idr;
+
+	rc = setup_afu_irq(ctx, irq);
+	if (rc)
+		goto err_alloc;
+
+	*irq_offset = irq_id_to_offset(ctx, irq->id);
+
+	mutex_unlock(&ctx->irq_lock);
+	return 0;
+
+err_alloc:
+	ocxl_link_free_irq(ctx->afu->fn->link, irq->hw_irq);
+err_idr:
+	idr_remove(&ctx->irq_idr, irq->id);
+err_unlock:
+	mutex_unlock(&ctx->irq_lock);
+	kfree(irq);
+	return rc;
+}
+
+static void afu_irq_free(struct afu_irq *irq, struct ocxl_context *ctx)
+{
+	if (ctx->mapping)
+		unmap_mapping_range(ctx->mapping,
+				irq_id_to_offset(ctx, irq->id),
+				1 << PAGE_SHIFT, 1);
+	release_afu_irq(irq);
+	if (irq->ev_ctx)
+		eventfd_ctx_put(irq->ev_ctx);
+	ocxl_link_free_irq(ctx->afu->fn->link, irq->hw_irq);
+	kfree(irq);
+}
+
+int ocxl_afu_irq_free(struct ocxl_context *ctx, u64 irq_offset)
+{
+	struct afu_irq *irq;
+	int id = irq_offset_to_id(ctx, irq_offset);
+
+	mutex_lock(&ctx->irq_lock);
+
+	irq = idr_find(&ctx->irq_idr, id);
+	if (!irq) {
+		mutex_unlock(&ctx->irq_lock);
+		return -EINVAL;
+	}
+	idr_remove(&ctx->irq_idr, irq->id);
+	afu_irq_free(irq, ctx);
+	mutex_unlock(&ctx->irq_lock);
+	return 0;
+}
+
+void ocxl_afu_irq_free_all(struct ocxl_context *ctx)
+{
+	struct afu_irq *irq;
+	int id;
+
+	mutex_lock(&ctx->irq_lock);
+	idr_for_each_entry(&ctx->irq_idr, irq, id)
+		afu_irq_free(irq, ctx);
+	mutex_unlock(&ctx->irq_lock);
+}
+
+int ocxl_afu_irq_set_fd(struct ocxl_context *ctx, u64 irq_offset, int eventfd)
+{
+	struct afu_irq *irq;
+	struct eventfd_ctx *ev_ctx;
+	int rc = 0, id = irq_offset_to_id(ctx, irq_offset);
+
+	mutex_lock(&ctx->irq_lock);
+	irq = idr_find(&ctx->irq_idr, id);
+	if (!irq) {
+		rc = -EINVAL;
+		goto unlock;
+	}
+
+	ev_ctx = eventfd_ctx_fdget(eventfd);
+	if (IS_ERR(ev_ctx)) {
+		rc = -EINVAL;
+		goto unlock;
+	}
+
+	irq->ev_ctx = ev_ctx;
+unlock:
+	mutex_unlock(&ctx->irq_lock);
+	return rc;
+}
+
+u64 ocxl_afu_irq_get_addr(struct ocxl_context *ctx, u64 irq_offset)
+{
+	struct afu_irq *irq;
+	int id = irq_offset_to_id(ctx, irq_offset);
+	u64 addr = 0;
+
+	mutex_lock(&ctx->irq_lock);
+	irq = idr_find(&ctx->irq_idr, id);
+	if (irq)
+		addr = irq->trigger_page;
+	mutex_unlock(&ctx->irq_lock);
+	return addr;
+}

drivers/misc/ocxl/context.c

@@ -31,6 +31,8 @@ int ocxl_context_init(struct ocxl_context *ctx, struct ocxl_afu *afu,
 	mutex_init(&ctx->mapping_lock);
 	init_waitqueue_head(&ctx->events_wq);
 	mutex_init(&ctx->xsl_error_lock);
+	mutex_init(&ctx->irq_lock);
+	idr_init(&ctx->irq_idr);
 	/*
 	 * Keep a reference on the AFU to make sure it's valid for the
 	 * duration of the life of the context
@@ -80,6 +82,19 @@ int ocxl_context_attach(struct ocxl_context *ctx, u64 amr)
 	return rc;
 }
 
+static int map_afu_irq(struct vm_area_struct *vma, unsigned long address,
+		u64 offset, struct ocxl_context *ctx)
+{
+	u64 trigger_addr;
+
+	trigger_addr = ocxl_afu_irq_get_addr(ctx, offset);
+	if (!trigger_addr)
+		return VM_FAULT_SIGBUS;
+
+	vm_insert_pfn(vma, address, trigger_addr >> PAGE_SHIFT);
+	return VM_FAULT_NOPAGE;
+}
+
 static int map_pp_mmio(struct vm_area_struct *vma, unsigned long address,
 		u64 offset, struct ocxl_context *ctx)
 {
@@ -118,7 +133,10 @@ static int ocxl_mmap_fault(struct vm_fault *vmf)
 	pr_debug("%s: pasid %d address 0x%lx offset 0x%llx\n", __func__,
 		ctx->pasid, vmf->address, offset);
 
+	if (offset < ctx->afu->irq_base_offset)
 		rc = map_pp_mmio(vma, vmf->address, offset, ctx);
+	else
+		rc = map_afu_irq(vma, vmf->address, offset, ctx);
 	return rc;
 }
 
@@ -126,6 +144,30 @@ static const struct vm_operations_struct ocxl_vmops = {
 	.fault = ocxl_mmap_fault,
 };
 
+static int check_mmap_afu_irq(struct ocxl_context *ctx,
+			struct vm_area_struct *vma)
+{
+	/* only one page */
+	if (vma_pages(vma) != 1)
+		return -EINVAL;
+
+	/* check offset validty */
+	if (!ocxl_afu_irq_get_addr(ctx, vma->vm_pgoff << PAGE_SHIFT))
+		return -EINVAL;
+
+	/*
+	 * trigger page should only be accessible in write mode.
+	 *
+	 * It's a bit theoretical, as a page mmaped with only
+	 * PROT_WRITE is currently readable, but it doesn't hurt.
+	 */
+	if ((vma->vm_flags & VM_READ) || (vma->vm_flags & VM_EXEC) ||
+		!(vma->vm_flags & VM_WRITE))
+		return -EINVAL;
+	vma->vm_flags &= ~(VM_MAYREAD | VM_MAYEXEC);
+	return 0;
+}
+
 static int check_mmap_mmio(struct ocxl_context *ctx,
 			struct vm_area_struct *vma)
 {
@@ -139,7 +181,10 @@ int ocxl_context_mmap(struct ocxl_context *ctx, struct vm_area_struct *vma)
 {
 	int rc;
 
+	if ((vma->vm_pgoff << PAGE_SHIFT) < ctx->afu->irq_base_offset)
 		rc = check_mmap_mmio(ctx, vma);
+	else
+		rc = check_mmap_afu_irq(ctx, vma);
 	if (rc)
 		return rc;
 
@@ -224,6 +269,8 @@ void ocxl_context_free(struct ocxl_context *ctx)
 	idr_remove(&ctx->afu->contexts_idr, ctx->pasid);
 	mutex_unlock(&ctx->afu->contexts_lock);
 
+	ocxl_afu_irq_free_all(ctx);
+	idr_destroy(&ctx->irq_idr);
 	/* reference to the AFU taken in ocxl_context_init */
 	ocxl_afu_put(ctx->afu);
 	kfree(ctx);

drivers/misc/ocxl/file.c

@@ -103,12 +103,17 @@ static long afu_ioctl_attach(struct ocxl_context *ctx,
 }
 
 #define CMD_STR(x) (x == OCXL_IOCTL_ATTACH ? "ATTACH" :			\
+			x == OCXL_IOCTL_IRQ_ALLOC ? "IRQ_ALLOC" :	\
+			x == OCXL_IOCTL_IRQ_FREE ? "IRQ_FREE" :		\
+			x == OCXL_IOCTL_IRQ_SET_FD ? "IRQ_SET_FD" :	\
 			"UNKNOWN")
 
 static long afu_ioctl(struct file *file, unsigned int cmd,
 		unsigned long args)
 {
 	struct ocxl_context *ctx = file->private_data;
+	struct ocxl_ioctl_irq_fd irq_fd;
+	u64 irq_offset;
 	long rc;
 
 	pr_debug("%s for context %d, command %s\n", __func__, ctx->pasid,
@@ -123,6 +128,35 @@ static long afu_ioctl(struct file *file, unsigned int cmd,
 				(struct ocxl_ioctl_attach __user *) args);
 		break;
 
+	case OCXL_IOCTL_IRQ_ALLOC:
+		rc = ocxl_afu_irq_alloc(ctx, &irq_offset);
+		if (!rc) {
+			rc = copy_to_user((u64 __user *) args, &irq_offset,
+					sizeof(irq_offset));
+			if (rc)
+				ocxl_afu_irq_free(ctx, irq_offset);
+		}
+		break;
+
+	case OCXL_IOCTL_IRQ_FREE:
+		rc = copy_from_user(&irq_offset, (u64 __user *) args,
+				sizeof(irq_offset));
+		if (rc)
+			return -EFAULT;
+		rc = ocxl_afu_irq_free(ctx, irq_offset);
+		break;
+
+	case OCXL_IOCTL_IRQ_SET_FD:
+		rc = copy_from_user(&irq_fd, (u64 __user *) args,
+				sizeof(irq_fd));
+		if (rc)
+			return -EFAULT;
+		if (irq_fd.reserved)
+			return -EINVAL;
+		rc = ocxl_afu_irq_set_fd(ctx, irq_fd.irq_offset,
+					irq_fd.eventfd);
+		break;
+
 	default:
 		rc = -EINVAL;
 	}

drivers/misc/ocxl/link.c

@@ -601,3 +601,31 @@ int ocxl_link_remove_pe(void *link_handle, int pasid)
 	mutex_unlock(&spa->spa_lock);
 	return rc;
 }
+
+int ocxl_link_irq_alloc(void *link_handle, int *hw_irq, u64 *trigger_addr)
+{
+	struct link *link = (struct link *) link_handle;
+	int rc, irq;
+	u64 addr;
+
+	if (atomic_dec_if_positive(&link->irq_available) < 0)
+		return -ENOSPC;
+
+	rc = pnv_ocxl_alloc_xive_irq(&irq, &addr);
+	if (rc) {
+		atomic_inc(&link->irq_available);
+		return rc;
+	}
+
+	*hw_irq = irq;
+	*trigger_addr = addr;
+	return 0;
+}
+
+void ocxl_link_free_irq(void *link_handle, int hw_irq)
+{
+	struct link *link = (struct link *) link_handle;
+
+	pnv_ocxl_free_xive_irq(hw_irq);
+	atomic_inc(&link->irq_available);
+}

drivers/misc/ocxl/ocxl_internal.h

@@ -190,4 +190,11 @@ extern void ocxl_context_free(struct ocxl_context *ctx);
 extern int ocxl_sysfs_add_afu(struct ocxl_afu *afu);
 extern void ocxl_sysfs_remove_afu(struct ocxl_afu *afu);
 
+extern int ocxl_afu_irq_alloc(struct ocxl_context *ctx, u64 *irq_offset);
+extern int ocxl_afu_irq_free(struct ocxl_context *ctx, u64 irq_offset);
+extern void ocxl_afu_irq_free_all(struct ocxl_context *ctx);
+extern int ocxl_afu_irq_set_fd(struct ocxl_context *ctx, u64 irq_offset,
+			int eventfd);
+extern u64 ocxl_afu_irq_get_addr(struct ocxl_context *ctx, u64 irq_offset);
+
 #endif /* _OCXL_INTERNAL_H_ */

include/uapi/misc/ocxl.h

@@ -32,9 +32,18 @@ struct ocxl_ioctl_attach {
 	__u64 reserved3;
 };
 
+struct ocxl_ioctl_irq_fd {
+	__u64 irq_offset;
+	__s32 eventfd;
+	__u32 reserved;
+};
+
 /* ioctl numbers */
 #define OCXL_MAGIC 0xCA
 /* AFU devices */
 #define OCXL_IOCTL_ATTACH	_IOW(OCXL_MAGIC, 0x10, struct ocxl_ioctl_attach)
+#define OCXL_IOCTL_IRQ_ALLOC	_IOR(OCXL_MAGIC, 0x11, __u64)
+#define OCXL_IOCTL_IRQ_FREE	_IOW(OCXL_MAGIC, 0x12, __u64)
+#define OCXL_IOCTL_IRQ_SET_FD	_IOW(OCXL_MAGIC, 0x13, struct ocxl_ioctl_irq_fd)
 
 #endif /* _UAPI_MISC_OCXL_H */