linux-kernel - [PATCH] drm/i915: check to see if the FPU is available before using it

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Message-Id: <20200328000422.98978-1-Jason@zx2c4.com>
Date:   Fri, 27 Mar 2020 18:04:22 -0600
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
        chris@...is-wilson.co.uk, linux-kernel@...r.kernel.org
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH] drm/i915: check to see if the FPU is available before using it

It's not safe to just grab the FPU willy nilly without first checking to
see if it's available. This patch adds the usual call to may_use_simd()
and falls back to boring memcpy if it's not available.

Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 drivers/gpu/drm/i915/i915_memcpy.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_memcpy.c b/drivers/gpu/drm/i915/i915_memcpy.c
index fdd550405fd3..7c0e022586bc 100644
--- a/drivers/gpu/drm/i915/i915_memcpy.c
+++ b/drivers/gpu/drm/i915/i915_memcpy.c
@@ -24,6 +24,7 @@
 
 #include <linux/kernel.h>
 #include <asm/fpu/api.h>
+#include <asm/simd.h>
 
 #include "i915_memcpy.h"
 
@@ -38,6 +39,12 @@ static DEFINE_STATIC_KEY_FALSE(has_movntdqa);
 #ifdef CONFIG_AS_MOVNTDQA
 static void __memcpy_ntdqa(void *dst, const void *src, unsigned long len)
 {
+	if (unlikely(!may_use_simd())) {
+		memcpy(dst, src, len);
+		return;
+	}
+
+
 	kernel_fpu_begin();
 
 	while (len >= 4) {
@@ -67,6 +74,11 @@ static void __memcpy_ntdqa(void *dst, const void *src, unsigned long len)
 
 static void __memcpy_ntdqu(void *dst, const void *src, unsigned long len)
 {
+	if (unlikely(!may_use_simd())) {
+		memcpy(dst, src, len);
+		return;
+	}
+
 	kernel_fpu_begin();
 
 	while (len >= 4) {
-- 
2.26.0