From: Rik van Riel <r...@surriel.com>

If the FPU state is not loaded in registers at fork time, memcpy the
fpstate from the parent task to the child task.

Signed-off-by: Rik van Riel <r...@surriel.com>
Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de>
---
 arch/x86/kernel/fpu/core.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 2ea85b32421a0..8564086c217fc 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -210,11 +210,14 @@ int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
         * ( The function 'fails' in the FNSAVE case, which destroys
         *   register contents so we have to copy them back. )
         */
-       if (!copy_fpregs_to_fpstate(dst_fpu)) {
+       __fpregs_changes_begin();
+       if (test_thread_flag(TIF_LOAD_FPU)) {
+               memcpy(&src_fpu->state, &dst_fpu->state, 
fpu_kernel_xstate_size);
+       } else if (!copy_fpregs_to_fpstate(dst_fpu)) {
                memcpy(&src_fpu->state, &dst_fpu->state, 
fpu_kernel_xstate_size);
                copy_kernel_to_fpregs(&src_fpu->state);
        }
-
+       __fpregs_changes_end();
        trace_x86_fpu_copy_src(src_fpu);
        trace_x86_fpu_copy_dst(dst_fpu);
 
-- 
2.19.0

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