In eager fpu mode, having deactivated fpu without immediately reloading some other context is illegal. Therefore, to recover from FNSAVE, we can't just deactivate the state -- we need to reload it if we're not actively context switching.
We had this wrong in fpu__save and fpu__copy. Fix both. __kernel_fpu_begin was fine -- add a comment. This fixes a warning triggerable with nofxsr eagerfpu=on. Signed-off-by: Andy Lutomirski <[email protected]> --- arch/x86/kernel/fpu/core.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 08e1e11a05ca..7a9244df33e2 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -114,6 +114,10 @@ void __kernel_fpu_begin(void) kernel_fpu_disable(); if (fpu->fpregs_active) { + /* + * Ignore return value -- we don't care if reg state + * is clobbered. + */ copy_fpregs_to_fpstate(fpu); } else { this_cpu_write(fpu_fpregs_owner_ctx, NULL); @@ -189,8 +193,12 @@ void fpu__save(struct fpu *fpu) preempt_disable(); if (fpu->fpregs_active) { - if (!copy_fpregs_to_fpstate(fpu)) - fpregs_deactivate(fpu); + if (!copy_fpregs_to_fpstate(fpu)) { + if (use_eager_fpu()) + copy_kernel_to_fpregs(&fpu->state); + else + fpregs_deactivate(fpu); + } } preempt_enable(); } @@ -259,7 +267,11 @@ static void fpu_copy(struct fpu *dst_fpu, struct fpu *src_fpu) preempt_disable(); if (!copy_fpregs_to_fpstate(dst_fpu)) { memcpy(&src_fpu->state, &dst_fpu->state, xstate_size); - fpregs_deactivate(src_fpu); + + if (use_eager_fpu()) + copy_kernel_to_fpregs(&src_fpu->state); + else + fpregs_deactivate(src_fpu); } preempt_enable(); } -- 2.5.0
