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Subject[RFC PATCH 09/10] x86/fpu: copy non-resident FPU state at fork time
Date
From: Rik van Riel <riel@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 <riel@surriel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@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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