|author||Linus Torvalds <email@example.com>||2006-10-03 09:45:46 -0700|
|committer||Linus Torvalds <firstname.lastname@example.org>||2006-10-03 09:47:14 -0700|
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 <email@example.com> Cc: Jesper Juhl <firstname.lastname@example.org> Cc: Andi Kleen <email@example.com> Signed-off-by: Linus Torvalds <firstname.lastname@example.org>
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/i386/kernel/cpu/common.c b/arch/i386/kernel/cpu/common.c
index 2799baaadf45..b2f24d57fddd 100644
@@ -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);