Booting a 486 with "no387 nofxsr" ends with | math_emulate: 0060:c101987d | Kernel panic - not syncing: Math emulation needed in kernel

on the first context switch in user land. The reason is that copy_fpregs_to_fpstate() tries `fnsave' which does not work. This happens since commit f1c8cd0176078 ("x86/fpu: Change fpu->fpregs_active users to fpu->fpstate_active").

Add a check for X86_FEATURE_FPU before trying to save FPU registers (we have such a check switch_fpu_finish() already).

Fixes: f1c8cd0176078 ("x86/fpu: Change fpu->fpregs_active users to fpu->fpstate_active") Cc: stable@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior bigeasy@linutronix.de --- arch/x86/include/asm/fpu/internal.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index a38bf5a1e37ad..69dcdf195b611 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -528,7 +528,7 @@ static inline void fpregs_activate(struct fpu *fpu) static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu) { - if (old_fpu->initialized) { + if (static_cpu_has(X86_FEATURE_FPU) && old_fpu->initialized) { if (!copy_fpregs_to_fpstate(old_fpu)) old_fpu->last_cpu = -1; else