xtensa: support coprocessors on SMP

Current coprocessor support on xtensa only works correctly on
uniprocessor configurations. Make it work on SMP too and keep it lazy.

Make coprocessor_owner array per-CPU and move it to struct exc_table for
easy access from the fast_coprocessor exception handler. Allow task to
have live coprocessors only on single CPU, record this CPU number in the
struct thread_info::cp_owner_cpu. Change struct thread_info::cpenable
meaning to be 'coprocessors live on cp_owner_cpu'.
Introduce C-level coprocessor exception handler that flushes and
releases live coprocessors of the task taking 'coprocessor disabled'
exception and call it from the fast_coprocessor handler when the task
has live coprocessors on other CPU.
Make coprocessor_flush_all and coprocessor_release_all work correctly
when called from any CPU by sending IPI to the cp_owner_cpu. Add
function coprocessor_flush_release_all to do flush followed by release
atomically. Add function local_coprocessors_flush_release_all to flush
and release all coprocessors on the local CPU and use it to flush
coprocessor contexts from the CPU that goes offline.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

3 files changed, 15 insertions, 2 deletions

diff --git a/arch/xtensa/include/asm/coprocessor.h b/arch/xtensa/include/asm/coprocessor.h
index a360efced7e7..3b1a0d5d2169 100644
--- a/arch/xtensa/include/asm/coprocessor.h
+++ b/arch/xtensa/include/asm/coprocessor.h
@@ -142,10 +142,12 @@ typedef struct { XCHAL_CP6_SA_LIST(2) } xtregs_cp6_t
 typedef struct { XCHAL_CP7_SA_LIST(2) } xtregs_cp7_t
 	__attribute__ ((aligned (XCHAL_CP7_SA_ALIGN)));
 
-extern struct thread_info* coprocessor_owner[XCHAL_CP_MAX];
+struct thread_info;
 void coprocessor_flush(struct thread_info *ti, int cp_index);
 void coprocessor_release_all(struct thread_info *ti);
 void coprocessor_flush_all(struct thread_info *ti);
+void coprocessor_flush_release_all(struct thread_info *ti);
+void local_coprocessors_flush_release_all(void);
 
 #endif	/* XTENSA_HAVE_COPROCESSORS */
 
diff --git a/arch/xtensa/include/asm/thread_info.h b/arch/xtensa/include/asm/thread_info.h
index f6fcbba1d02f..52974317a6b6 100644
--- a/arch/xtensa/include/asm/thread_info.h
+++ b/arch/xtensa/include/asm/thread_info.h
@@ -52,12 +52,17 @@ struct thread_info {
 	__u32			cpu;		/* current CPU */
 	__s32			preempt_count;	/* 0 => preemptable,< 0 => BUG*/
 
-	unsigned long		cpenable;
 #if XCHAL_HAVE_EXCLUSIVE
 	/* result of the most recent exclusive store */
 	unsigned long		atomctl8;
 #endif
 
+	/*
+	 * If i-th bit is set then coprocessor state is loaded into the
+	 * coprocessor i on CPU cp_owner_cpu.
+	 */
+	unsigned long		cpenable;
+	u32			cp_owner_cpu;
 	/* Allocate storage for extra user states and coprocessor states. */
 #if XTENSA_HAVE_COPROCESSORS
 	xtregs_coprocessor_t	xtregs_cp;
diff --git a/arch/xtensa/include/asm/traps.h b/arch/xtensa/include/asm/traps.h
index 514376eff58c..6f74ccc0c7ea 100644
--- a/arch/xtensa/include/asm/traps.h
+++ b/arch/xtensa/include/asm/traps.h
@@ -27,6 +27,10 @@ struct exc_table {
 	void *fixup;
 	/* For passing a parameter to fixup */
 	void *fixup_param;
+#if XTENSA_HAVE_COPROCESSORS
+	/* Pointers to owner struct thread_info */
+	struct thread_info *coprocessor_owner[XCHAL_CP_MAX];
+#endif
 	/* Fast user exception handlers */
 	void *fast_user_handler[EXCCAUSE_N];
 	/* Fast kernel exception handlers */
@@ -35,6 +39,8 @@ struct exc_table {
 	xtensa_exception_handler *default_handler[EXCCAUSE_N];
 };
 
+DECLARE_PER_CPU(struct exc_table, exc_table);
+
 xtensa_exception_handler *
 __init trap_set_handler(int cause, xtensa_exception_handler *handler);