From 3dad29fb4b085a159d26e2322dc07b46950ff72e Mon Sep 17 00:00:00 2001
From: Matthew Macy <mmacy@freebsd.org>
Date: Wed, 23 Sep 2020 11:09:48 -0700
Subject: [PATCH] FreeBSD: Don't save user FPU context in kernel threads

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Ryan Moeller <freqlabs@FreeBSD.org>
Signed-off-by: Matt Macy <mmacy@FreeBSD.org>
Closes #10899
---
 include/os/freebsd/spl/sys/simd_x86.h | 16 ++++++++--------
 module/os/freebsd/spl/spl_taskq.c     |  4 ++++
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/include/os/freebsd/spl/sys/simd_x86.h b/include/os/freebsd/spl/sys/simd_x86.h
index a35e205d5a..63d6017b79 100644
--- a/include/os/freebsd/spl/sys/simd_x86.h
+++ b/include/os/freebsd/spl/sys/simd_x86.h
@@ -29,6 +29,7 @@
 #include <sys/cdefs.h>
 #include <sys/types.h>
 #include <sys/systm.h>
+#include <sys/proc.h>
 #ifdef __i386__
 #include <x86/fpu.h>
 #else
@@ -42,16 +43,15 @@
 #define	kfpu_allowed()		1
 #define	kfpu_initialize(tsk)	do {} while (0)
 
-#define	kfpu_begin() {							\
-	critical_enter();					\
-	fpu_kern_enter(curthread, NULL, FPU_KERN_NOCTX); \
+#define	kfpu_begin() {					\
+	if (__predict_false(!is_fpu_kern_thread(0)))		\
+		fpu_kern_enter(curthread, NULL, FPU_KERN_NOCTX);\
 }
 
-#define	kfpu_end()						\
-	{						 \
-		fpu_kern_leave(curthread, NULL); \
-		critical_exit();			     \
-	}
+#define	kfpu_end()	{			\
+	if (__predict_false(curpcb->pcb_flags & PCB_FPUNOSAVE))	\
+		fpu_kern_leave(curthread, NULL);	\
+}
 
 /*
  * Check if OS supports AVX and AVX2 by checking XCR0
diff --git a/module/os/freebsd/spl/spl_taskq.c b/module/os/freebsd/spl/spl_taskq.c
index 049e889cf3..cc025de959 100644
--- a/module/os/freebsd/spl/spl_taskq.c
+++ b/module/os/freebsd/spl/spl_taskq.c
@@ -169,6 +169,10 @@ taskq_tsd_set(void *context)
 {
 	taskq_t *tq = context;
 
+#if defined(__amd64__) || defined(__i386__) || defined(__aarch64__)
+	if (context != NULL && tsd_get(taskq_tsd) == NULL)
+		fpu_kern_thread(FPU_KERN_NORMAL);
+#endif
 	tsd_set(taskq_tsd, tq);
 }