4.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: Andy Lutomirski <l...@kernel.org> commit f363938c70a04e6bc99023a5e0c44ef7879b903f upstream. After fixing FPU option parsing, we now parse the 'no387' boot option too early: no387 clears X86_FEATURE_FPU before it's even probed, so the boot CPU promptly re-enables it. I suspect it gets even more confused on SMP. Fix the probing code to leave X86_FEATURE_FPU off if it's been disabled by setup_clear_cpu_cap(). Signed-off-by: Andy Lutomirski <l...@kernel.org> Cc: Andy Lutomirski <l...@amacapital.net> Cc: Borislav Petkov <b...@alien8.de> Cc: Brian Gerst <brge...@gmail.com> Cc: Dave Hansen <dave.han...@linux.intel.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: Fenghua Yu <fenghua...@intel.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Oleg Nesterov <o...@redhat.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Quentin Casasnovas <quentin.casasno...@oracle.com> Cc: Sai Praneeth Prakhya <sai.praneeth.prak...@intel.com> Cc: Thomas Gleixner <t...@linutronix.de> Cc: yu-cheng yu <yu-cheng...@intel.com> Fixes: 4f81cbafcce2 ("x86/fpu: Fix early FPU command-line parsing") Signed-off-by: Ingo Molnar <mi...@kernel.org> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- arch/x86/kernel/fpu/init.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) --- a/arch/x86/kernel/fpu/init.c +++ b/arch/x86/kernel/fpu/init.c @@ -78,13 +78,15 @@ static void fpu__init_system_early_gener cr0 &= ~(X86_CR0_TS | X86_CR0_EM); write_cr0(cr0); - asm volatile("fninit ; fnstsw %0 ; fnstcw %1" - : "+m" (fsw), "+m" (fcw)); + if (!test_bit(X86_FEATURE_FPU, (unsigned long *)cpu_caps_cleared)) { + asm volatile("fninit ; fnstsw %0 ; fnstcw %1" + : "+m" (fsw), "+m" (fcw)); - if (fsw == 0 && (fcw & 0x103f) == 0x003f) - set_cpu_cap(c, X86_FEATURE_FPU); - else - clear_cpu_cap(c, X86_FEATURE_FPU); + if (fsw == 0 && (fcw & 0x103f) == 0x003f) + set_cpu_cap(c, X86_FEATURE_FPU); + else + clear_cpu_cap(c, X86_FEATURE_FPU); + } #ifndef CONFIG_MATH_EMULATION if (!cpu_has_fpu) {