From db52ef74b35dcb91fd154fa52c618bdd1b90e28e Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Sat, 27 Jun 2015 10:25:14 +0200 Subject: [PATCH] x86/fpu: Fix FPU related boot regression when CPUID masking BIOS feature is enabled Mike Galbraith reported: " My i7-4790 box is having one hell of a time with this merge window, dead in the water. BIOS setting "Limit CPUID Maximum" upsets new fpu code mightily. " It turns out that Linux does a double workaround here, as per: 066941bd4eeb ("x86: unmask CPUID levels on Intel CPUs") it undoes the BIOS workaround - but as a side effect the CPUID state is not completely constant during early init anymore, and the new FPU init code did not take this into account. So what happened is that the xstate init code did not have full CPUID available, which broke subsequent attempts to use xstate features. Fix this by ordering the early FPU init code to after we've stabilized the CPUID state. Reported-bisected-and-tested-by: Mike Galbraith Cc: Andrew Morton Cc: Borislav Petkov Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20150627082514.GA10894@gmail.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/common.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 9fc5e3d9d9c8..922c5e0cea4c 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -742,7 +742,6 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) cpu_detect(c); get_cpu_vendor(c); get_cpu_cap(c); - fpu__init_system(c); if (this_cpu->c_early_init) this_cpu->c_early_init(c); @@ -754,6 +753,7 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) this_cpu->c_bsp_init(c); setup_force_cpu_cap(X86_FEATURE_ALWAYS); + fpu__init_system(c); } void __init early_cpu_init(void) -- 2.20.1