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>

1 files changed, 197 insertions, 0 deletions

diff --git a/drivers/misc/ocxl/afu_irq.c b/drivers/misc/ocxl/afu_irq.c
new file mode 100644
index 000000000000..f40d853de401
--- /dev/null
+++ b/drivers/misc/ocxl/afu_irq.c
@@ -0,0 +1,197 @@
+// 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;
+}