From 8ccb3dcd1f8e80e8702642e1de26541b52f6bb7c Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 3 Oct 2006 09:45:46 -0700 Subject: [PATCH] x86: Fix booting with "no387 nofxsr" Jesper Juhl reported that testing the software math-emulation by forcing "no387" doesn't work on modern CPU's. The reason was two-fold: - you also need to pass in "nofxsr" to make sure that we not only don't touch the old i387 legacy hardware, it also needs to disable the modern XMM/FXSR sequences - "nofxsr" didn't actually clear the capability bits immediately, leaving the early boot sequence still using FXSR until we got to the identify_cpu() stage. This fixes the "nofxsr" flag to take effect immediately on the boot CPU. Debugging by Randy Dunlap Acked-by: Randy Dunlap Cc: Jesper Juhl Cc: Andi Kleen Signed-off-by: Linus Torvalds --- arch/i386/kernel/cpu/common.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/i386/kernel/cpu/common.c b/arch/i386/kernel/cpu/common.c index 2799baaadf..b2f24d57fd 100644 --- a/arch/i386/kernel/cpu/common.c +++ b/arch/i386/kernel/cpu/common.c @@ -184,7 +184,16 @@ static void __cpuinit get_cpu_vendor(struct cpuinfo_x86 *c, int early) static int __init x86_fxsr_setup(char * s) { + /* Tell all the other CPU's to not use it... */ disable_x86_fxsr = 1; + + /* + * ... and clear the bits early in the boot_cpu_data + * so that the bootup process doesn't try to do this + * either. + */ + clear_bit(X86_FEATURE_FXSR, boot_cpu_data.x86_capability); + clear_bit(X86_FEATURE_XMM, boot_cpu_data.x86_capability); return 1; } __setup("nofxsr", x86_fxsr_setup); -- 2.39.5