The default kernel_fpu_begin() doesn't work on systems that support XMM but
haven't yet enabled OSFXSR. This causes crashes when _mmx_memcpy() is
called too early.
Fix it by using kernel_fpu_begin(KFPU_MMX) explicitly. This should also be
faster, since it skips both the reasonably fast LDMXCSR and also the rather
slow FNINIT instructions.
Fixes: 7ad816762f9b ("x86/fpu: Reset MXCSR to default in kernel_fpu_begin()")
Reported-by: Krzysztof Mazur <krzys...@podlesie.net>
Signed-off-by: Andy Lutomirski <l...@kernel.org>
---
arch/x86/lib/mmx_32.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/arch/x86/lib/mmx_32.c b/arch/x86/lib/mmx_32.c
index 4321fa02e18d..daa80fa005fb 100644
--- a/arch/x86/lib/mmx_32.c
+++ b/arch/x86/lib/mmx_32.c
@@ -37,7 +37,7 @@ void *_mmx_memcpy(void *to, const void *from, size_t len)
p = to;
i = len >> 6; /* len/64 */
- kernel_fpu_begin();
+ kernel_fpu_begin_mask(KFPU_MMX);
__asm__ __volatile__ (
"1: prefetch (%0)\n" /* This set is 28 bytes */
@@ -127,7 +127,7 @@ static void fast_clear_page(void *page)
{
int i;
- kernel_fpu_begin();
+ kernel_fpu_begin_mask(KFPU_MMX);
__asm__ __volatile__ (
" pxor %%mm0, %%mm0\n" : :
@@ -160,7 +160,7 @@ static void fast_copy_page(void *to, void *from)
{
int i;
- kernel_fpu_begin();
+ kernel_fpu_begin_mask(KFPU_MMX);
/*
* maybe the prefetch stuff can go before the expensive fnsave...
@@ -247,7 +247,7 @@ static void fast_clear_page(void *page)
{
int i;
- kernel_fpu_begin();
+ kernel_fpu_begin_mask(KFPU_MMX);
__asm__ __volatile__ (
" pxor %%mm0, %%mm0\n" : :
@@ -282,7 +282,7 @@ static void fast_copy_page(void *to, void *from)
{
int i;
- kernel_fpu_begin();
+ kernel_fpu_begin_mask(KFPU_MMX);
__asm__ __volatile__ (
"1: prefetch (%0)\n"
--
2.29.2
