cxl: Add support for ASB_Notify on POWER9

The POWER9 core supports a new feature: ASB_Notify which requires the
support of the Special Purpose Register: TIDR.

The ASB_Notify command, generated by the AFU, will attempt to
wake-up the host thread identified by the particular LPID:PID:TID.

This patch assign a unique TIDR (thread id) for the current thread which
will be used in the process element entry.
Signed-off-by: Christophe Lombard <clombard@linux.vnet.ibm.com>
Reviewed-by: Philippe Bergheaud <felix@linux.vnet.ibm.com>
Acked-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Reviewed-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Acked-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/process.c

@@ -1590,6 +1590,7 @@ int set_thread_tidr(struct task_struct *t)
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(set_thread_tidr);
 
 #endif /* CONFIG_PPC64 */
 

drivers/misc/cxl/context.c

@@ -45,6 +45,8 @@ int cxl_context_init(struct cxl_context *ctx, struct cxl_afu *afu, bool master)
 	ctx->pid = NULL; /* Set in start work ioctl */
 	mutex_init(&ctx->mapping_lock);
 	ctx->mapping = NULL;
+	ctx->tidr = 0;
+	ctx->assign_tidr = false;
 
 	if (cxl_is_power8()) {
 		spin_lock_init(&ctx->sste_lock);

drivers/misc/cxl/cxl.h

@@ -630,6 +630,9 @@ struct cxl_context {
 	struct list_head extra_irq_contexts;
 
 	struct mm_struct *mm;
+
+	u16 tidr;
+	bool assign_tidr;
 };
 
 struct cxl_irq_info;

drivers/misc/cxl/cxllib.c

@@ -199,10 +199,11 @@ int cxllib_get_PE_attributes(struct task_struct *task,
 		 */
 		attr->pid = mm->context.id;
 		mmput(mm);
+		attr->tid = task->thread.tidr;
 	} else {
 		attr->pid = 0;
+		attr->tid = 0;
 	}
-	attr->tid = 0;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(cxllib_get_PE_attributes);

drivers/misc/cxl/file.c

@@ -173,7 +173,7 @@ static long afu_ioctl_start_work(struct cxl_context *ctx,
 	 * flags are set it's invalid
 	 */
 	if (work.reserved1 || work.reserved2 || work.reserved3 ||
-	    work.reserved4 || work.reserved5 || work.reserved6 ||
+	    work.reserved4 || work.reserved5 ||
 	    (work.flags & ~CXL_START_WORK_ALL)) {
 		rc = -EINVAL;
 		goto out;
@@ -186,12 +186,16 @@ static long afu_ioctl_start_work(struct cxl_context *ctx,
 		rc =  -EINVAL;
 		goto out;
 	}
+
 	if ((rc = afu_register_irqs(ctx, work.num_interrupts)))
 		goto out;
 
 	if (work.flags & CXL_START_WORK_AMR)
 		amr = work.amr & mfspr(SPRN_UAMOR);
 
+	if (work.flags & CXL_START_WORK_TID)
+		ctx->assign_tidr = true;
+
 	ctx->mmio_err_ff = !!(work.flags & CXL_START_WORK_ERR_FF);
 
 	/*
@@ -263,8 +267,15 @@ static long afu_ioctl_start_work(struct cxl_context *ctx,
 		goto out;
 	}
 
-	ctx->status = STARTED;
 	rc = 0;
+	if (work.flags & CXL_START_WORK_TID) {
+		work.tid = ctx->tidr;
+		if (copy_to_user(uwork, &work, sizeof(work)))
+			rc = -EFAULT;
+	}
+
+	ctx->status = STARTED;
+
 out:
 	mutex_unlock(&ctx->status_mutex);
 	return rc;

drivers/misc/cxl/native.c

@@ -16,6 +16,7 @@
 #include <linux/uaccess.h>
 #include <linux/delay.h>
 #include <asm/synch.h>
+#include <asm/switch_to.h>
 #include <misc/cxl-base.h>
 
 #include "cxl.h"
@@ -655,6 +656,7 @@ static void update_ivtes_directed(struct cxl_context *ctx)
 static int process_element_entry_psl9(struct cxl_context *ctx, u64 wed, u64 amr)
 {
 	u32 pid;
+	int rc;
 
 	cxl_assign_psn_space(ctx);
 
@@ -673,7 +675,16 @@ static int process_element_entry_psl9(struct cxl_context *ctx, u64 wed, u64 amr)
 		pid = ctx->mm->context.id;
 	}
 
-	ctx->elem->common.tid = 0;
+	/* Assign a unique TIDR (thread id) for the current thread */
+	if (!(ctx->tidr) && (ctx->assign_tidr)) {
+		rc = set_thread_tidr(current);
+		if (rc)
+			return -ENODEV;
+		ctx->tidr = current->thread.tidr;
+		pr_devel("%s: current tidr: %d\n", __func__, ctx->tidr);
+	}
+
+	ctx->elem->common.tid = cpu_to_be32(ctx->tidr);
 	ctx->elem->common.pid = cpu_to_be32(pid);
 
 	ctx->elem->sr = cpu_to_be64(calculate_sr(ctx));

include/uapi/misc/cxl.h

@@ -20,20 +20,22 @@ struct cxl_ioctl_start_work {
 	__u64 work_element_descriptor;
 	__u64 amr;
 	__s16 num_interrupts;
-	__s16 reserved1;
-	__s32 reserved2;
+	__u16 tid;
+	__s32 reserved1;
+	__u64 reserved2;
 	__u64 reserved3;
 	__u64 reserved4;
 	__u64 reserved5;
-	__u64 reserved6;
 };
 
 #define CXL_START_WORK_AMR		0x0000000000000001ULL
 #define CXL_START_WORK_NUM_IRQS		0x0000000000000002ULL
 #define CXL_START_WORK_ERR_FF		0x0000000000000004ULL
+#define CXL_START_WORK_TID		0x0000000000000008ULL
 #define CXL_START_WORK_ALL		(CXL_START_WORK_AMR |\
 					 CXL_START_WORK_NUM_IRQS |\
-					 CXL_START_WORK_ERR_FF)
+					 CXL_START_WORK_ERR_FF |\
+					 CXL_START_WORK_TID)
 
 
 /* Possible modes that an afu can be in */