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-rw-r--r--arch/x86/kernel/head_32.S9
1 files changed, 7 insertions, 2 deletions
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 957a47aec64e..4dac2f68ed4a 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -292,8 +292,8 @@ default_entry:
* be using the global pages.
*
* NOTE! If we are on a 486 we may have no cr4 at all!
- * Specifically, cr4 exists if and only if CPUID exists,
- * which in turn exists if and only if EFLAGS.ID exists.
+ * Specifically, cr4 exists if and only if CPUID exists
+ * and has flags other than the FPU flag set.
*/
movl $X86_EFLAGS_ID,%ecx
pushl %ecx
@@ -308,6 +308,11 @@ default_entry:
testl %ecx,%eax
jz 6f # No ID flag = no CPUID = no CR4
+ movl $1,%eax
+ cpuid
+ andl $~1,%edx # Ignore CPUID.FPU
+ jz 6f # No flags or only CPUID.FPU = no CR4
+
movl pa(mmu_cr4_features),%eax
movl %eax,%cr4