ocxl: Expose the thread_id needed for wait on POWER9

In order to successfully issue as_notify, an AFU needs to know the TID
to notify, which in turn means that this information should be
available in userspace so it can be communicated to the AFU.

Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
Acked-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

drivers/misc/ocxl/context.c

@@ -34,6 +34,8 @@ int ocxl_context_init(struct ocxl_context *ctx, struct ocxl_afu *afu,
 	mutex_init(&ctx->xsl_error_lock);
 	mutex_init(&ctx->irq_lock);
 	idr_init(&ctx->irq_idr);
+	ctx->tidr = 0;
+
 	/*
 	 * Keep a reference on the AFU to make sure it's valid for the
 	 * duration of the life of the context
@@ -65,6 +67,7 @@ int ocxl_context_attach(struct ocxl_context *ctx, u64 amr)
 {
 	int rc;
 
+	// Locks both status & tidr
 	mutex_lock(&ctx->status_mutex);
 	if (ctx->status != OPENED) {
 		rc = -EIO;
@@ -72,7 +75,7 @@ int ocxl_context_attach(struct ocxl_context *ctx, u64 amr)
 	}
 
 	rc = ocxl_link_add_pe(ctx->afu->fn->link, ctx->pasid,
-			current->mm->context.id, 0, amr, current->mm,
+			current->mm->context.id, ctx->tidr, amr, current->mm,
 			xsl_fault_error, ctx);
 	if (rc)
 		goto out;

drivers/misc/ocxl/file.c

@@ -5,6 +5,8 @@
 #include <linux/sched/signal.h>
 #include <linux/uaccess.h>
 #include <uapi/misc/ocxl.h>
+#include <asm/reg.h>
+#include <asm/switch_to.h>
 #include "ocxl_internal.h"
 
 
@@ -123,11 +125,55 @@ static long afu_ioctl_get_metadata(struct ocxl_context *ctx,
 	return 0;
 }
 
+#ifdef CONFIG_PPC64
+static long afu_ioctl_enable_p9_wait(struct ocxl_context *ctx,
+		struct ocxl_ioctl_p9_wait __user *uarg)
+{
+	struct ocxl_ioctl_p9_wait arg;
+
+	memset(&arg, 0, sizeof(arg));
+
+	if (cpu_has_feature(CPU_FTR_P9_TIDR)) {
+		enum ocxl_context_status status;
+
+		// Locks both status & tidr
+		mutex_lock(&ctx->status_mutex);
+		if (!ctx->tidr) {
+			if (set_thread_tidr(current))
+				return -ENOENT;
+
+			ctx->tidr = current->thread.tidr;
+		}
+
+		status = ctx->status;
+		mutex_unlock(&ctx->status_mutex);
+
+		if (status == ATTACHED) {
+			int rc;
+			struct link *link = ctx->afu->fn->link;
+
+			rc = ocxl_link_update_pe(link, ctx->pasid, ctx->tidr);
+			if (rc)
+				return rc;
+		}
+
+		arg.thread_id = ctx->tidr;
+	} else
+		return -ENOENT;
+
+	if (copy_to_user(uarg, &arg, sizeof(arg)))
+		return -EFAULT;
+
+	return 0;
+}
+#endif
+
 #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" :	\
 			x == OCXL_IOCTL_GET_METADATA ? "GET_METADATA" :	\
+			x == OCXL_IOCTL_ENABLE_P9_WAIT ? "ENABLE_P9_WAIT" :	\
 			"UNKNOWN")
 
 static long afu_ioctl(struct file *file, unsigned int cmd,
@@ -186,6 +232,13 @@ static long afu_ioctl(struct file *file, unsigned int cmd,
 				(struct ocxl_ioctl_metadata __user *) args);
 		break;
 
+#ifdef CONFIG_PPC64
+	case OCXL_IOCTL_ENABLE_P9_WAIT:
+		rc = afu_ioctl_enable_p9_wait(ctx,
+				(struct ocxl_ioctl_p9_wait __user *) args);
+		break;
+#endif
+
 	default:
 		rc = -EINVAL;
 	}

drivers/misc/ocxl/link.c

@@ -544,6 +544,42 @@ unlock:
 }
 EXPORT_SYMBOL_GPL(ocxl_link_add_pe);
 
+int ocxl_link_update_pe(void *link_handle, int pasid, __u16 tid)
+{
+	struct link *link = (struct link *) link_handle;
+	struct spa *spa = link->spa;
+	struct ocxl_process_element *pe;
+	int pe_handle, rc;
+
+	if (pasid > SPA_PASID_MAX)
+		return -EINVAL;
+
+	pe_handle = pasid & SPA_PE_MASK;
+	pe = spa->spa_mem + pe_handle;
+
+	mutex_lock(&spa->spa_lock);
+
+	pe->tid = tid;
+
+	/*
+	 * The barrier makes sure the PE is updated
+	 * before we clear the NPU context cache below, so that the
+	 * old PE cannot be reloaded erroneously.
+	 */
+	mb();
+
+	/*
+	 * hook to platform code
+	 * On powerpc, the entry needs to be cleared from the context
+	 * cache of the NPU.
+	 */
+	rc = pnv_ocxl_spa_remove_pe_from_cache(link->platform_data, pe_handle);
+	WARN_ON(rc);
+
+	mutex_unlock(&spa->spa_lock);
+	return rc;
+}
+
 int ocxl_link_remove_pe(void *link_handle, int pasid)
 {
 	struct link *link = (struct link *) link_handle;

drivers/misc/ocxl/ocxl_internal.h

@@ -77,6 +77,7 @@ struct ocxl_context {
 	struct ocxl_xsl_error xsl_error;
 	struct mutex irq_lock;
 	struct idr irq_idr;
+	u16 tidr; // Thread ID used for P9 wait implementation
 };
 
 struct ocxl_process_element {