4.4-stable review patch. If anyone has any objections, please let me know.
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From: Andy Lutomirski luto@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 luto@kernel.org Cc: Andy Lutomirski luto@amacapital.net Cc: Borislav Petkov bp@alien8.de Cc: Brian Gerst brgerst@gmail.com Cc: Dave Hansen dave.hansen@linux.intel.com Cc: Denys Vlasenko dvlasenk@redhat.com Cc: Fenghua Yu fenghua.yu@intel.com Cc: H. Peter Anvin hpa@zytor.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Oleg Nesterov oleg@redhat.com Cc: Peter Zijlstra peterz@infradead.org Cc: Quentin Casasnovas quentin.casasnovas@oracle.com Cc: Sai Praneeth Prakhya sai.praneeth.prakhya@intel.com Cc: Thomas Gleixner tglx@linutronix.de Cc: yu-cheng yu yu-cheng.yu@intel.com Fixes: 4f81cbafcce2 ("x86/fpu: Fix early FPU command-line parsing") Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@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) {