Re: [PATCH 2/2] cxl: Enable global TLBIs for cxl contexts

    
Signed-off-by: Frederic Barrat <redacted>

diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index 309592589e30..6447c0df7ec4 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h

@@ -77,6 +77,41 @@ extern void switch_cop(struct mm_struct *next);
 extern int use_cop(unsigned long acop, struct mm_struct *mm);
 extern void drop_cop(unsigned long acop, struct mm_struct *mm);
 
+#ifdef CONFIG_PPC_BOOK3S_64
+static inline void inc_mm_active_cpus(struct mm_struct *mm)
+{
+	atomic_inc(&mm->context.active_cpus);
+}
+
+static inline void dec_mm_active_cpus(struct mm_struct *mm)
+{
+	atomic_dec(&mm->context.active_cpus);
+}
+
+static inline void mm_context_add_copro(struct mm_struct *mm)
+{
+	inc_mm_active_cpus(mm);
+}
+
+static inline void mm_context_remove_copro(struct mm_struct *mm)
+{
+	/*
+	 * Need to broadcast a global flush of the full mm before
+	 * decrementing active_cpus count, as the next TLBI may be
+	 * local and the nMMU and/or PSL need to be cleaned up.
+	 * Should be rare enough so that it's acceptable.
+	 */
+	flush_tlb_mm(mm);
+	dec_mm_active_cpus(mm);
+}

+#else
+static inline void inc_mm_active_cpus(struct mm_struct *mm) { }
+static inline void dec_mm_active_cpus(struct mm_struct *mm) { }
+static inline void mm_context_add_copro(struct mm_struct *mm) { }
+static inline void mm_context_remove_copro(struct mm_struct *mm) { }
+#endif
+
+
 extern void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 			       struct task_struct *tsk);
 

diff --git a/arch/powerpc/mm/mmu_context.c b/arch/powerpc/mm/mmu_context.c
index 0f613bc63c50..d60a62bf4fc7 100644
--- a/arch/powerpc/mm/mmu_context.c
+++ b/arch/powerpc/mm/mmu_context.c

@@ -34,15 +34,6 @@ static inline void switch_mm_pgdir(struct task_struct *tsk,
 				   struct mm_struct *mm) { }
 #endif
 
-#ifdef CONFIG_PPC_BOOK3S_64
-static inline void inc_mm_active_cpus(struct mm_struct *mm)
-{
-	atomic_inc(&mm->context.active_cpus);
-}
-#else
-static inline void inc_mm_active_cpus(struct mm_struct *mm) { }
-#endif
-
 void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 			struct task_struct *tsk)
 {

diff --git a/drivers/misc/cxl/api.c b/drivers/misc/cxl/api.c
index e0dfd1eadd70..33daf33e0e05 100644
--- a/drivers/misc/cxl/api.c
+++ b/drivers/misc/cxl/api.c

@@ -15,6 +15,7 @@
 #include <linux/module.h>
 #include <linux/mount.h>
 #include <linux/sched/mm.h>
+#include <linux/mmu_context.h>
 
 #include "cxl.h"
 

@@ -332,8 +333,11 @@ int cxl_start_context(struct cxl_context *ctx, u64 wed,
 		cxl_context_mm_count_get(ctx);
 
 		/* decrement the use count */
-		if (ctx->mm)
+		if (ctx->mm) {
 			mmput(ctx->mm);
+			/* make TLBIs for this context global */
+			mm_context_add_copro(ctx->mm);
+		}
 	}
 
 	/*

@@ -342,13 +346,25 @@ int cxl_start_context(struct cxl_context *ctx, u64 wed,
 	 */
 	cxl_ctx_get();
 
+	/*
+	 * Barrier is needed to make sure all TLBIs are global before
+	 * we attach and the context starts being used by the adapter.
+	 *
+	 * Needed after mm_context_add_copro() for radix and
+	 * cxl_ctx_get() for hash/p8
+	 */
+	smp_mb();
+
 	if ((rc = cxl_ops->attach_process(ctx, kernel, wed, 0))) {
 		put_pid(ctx->pid);
 		ctx->pid = NULL;
 		cxl_adapter_context_put(ctx->afu->adapter);
 		cxl_ctx_put();
-		if (task)
+		if (task) {
 			cxl_context_mm_count_put(ctx);
+			if (ctx->mm)
+				mm_context_remove_copro(ctx->mm);
+		}
 		goto out;
 	}
 

diff --git a/drivers/misc/cxl/context.c b/drivers/misc/cxl/context.c
index 8c32040b9c09..12a41b2753f0 100644
--- a/drivers/misc/cxl/context.c
+++ b/drivers/misc/cxl/context.c

@@ -18,6 +18,7 @@
 #include <linux/slab.h>
 #include <linux/idr.h>
 #include <linux/sched/mm.h>
+#include <linux/mmu_context.h>
 #include <asm/cputable.h>
 #include <asm/current.h>
 #include <asm/copro.h>

@@ -267,6 +268,8 @@ int __detach_context(struct cxl_context *ctx)
 
 	/* Decrease the mm count on the context */
 	cxl_context_mm_count_put(ctx);
+	if (ctx->mm)
+		mm_context_remove_copro(ctx->mm);
 	ctx->mm = NULL;
 
 	return 0;

diff --git a/drivers/misc/cxl/file.c b/drivers/misc/cxl/file.c
index b76a491a485d..411e83cbbd82 100644
--- a/drivers/misc/cxl/file.c
+++ b/drivers/misc/cxl/file.c

@@ -19,6 +19,7 @@
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/sched/mm.h>
+#include <linux/mmu_context.h>
 #include <asm/cputable.h>
 #include <asm/current.h>
 #include <asm/copro.h>

@@ -220,9 +221,12 @@ static long afu_ioctl_start_work(struct cxl_context *ctx,
 	/* ensure this mm_struct can't be freed */
 	cxl_context_mm_count_get(ctx);
 
-	/* decrement the use count */
-	if (ctx->mm)
+	if (ctx->mm) {
+		/* decrement the use count */
 		mmput(ctx->mm);
+		/* make TLBIs for this context global */
+		mm_context_add_copro(ctx->mm);
+	}
 
 	/*
 	 * Increment driver use count. Enables global TLBIs for hash

@@ -230,6 +234,15 @@ static long afu_ioctl_start_work(struct cxl_context *ctx,
 	 */
 	cxl_ctx_get();
 
+	/*
+	 * Barrier is needed to make sure all TLBIs are global before
+	 * we attach and the context starts being used by the adapter.
+	 *
+	 * Needed after mm_context_add_copro() for radix and
+	 * cxl_ctx_get() for hash/p8
+	 */
+	smp_mb();
+
 	trace_cxl_attach(ctx, work.work_element_descriptor, work.num_interrupts, amr);
 
 	if ((rc = cxl_ops->attach_process(ctx, false, work.work_element_descriptor,

@@ -240,6 +253,8 @@ static long afu_ioctl_start_work(struct cxl_context *ctx,
 		ctx->pid = NULL;
 		cxl_ctx_put();
 		cxl_context_mm_count_put(ctx);
+		if (ctx->mm)
+			mm_context_remove_copro(ctx->mm);
 		goto out;
 	}