[Xen-devel] [PATCH v4 2/4] Revert "x86/boot: Fail the boot if !M486 and CPUID is missing"

[Andy Lutomirski <luto@xxxxxxxxxx>]

This reverts commit ed68d7e9b9cfb64f3045ffbcb108df03c09a0f98.

The patch wasn't quite correct -- there are non-Intel (and hence
non-486) CPUs that we support that don't have CPUID.  Since we no
longer require CPUID for sync_core(), just revert the patch.

I think the relevant CPUs are Geode and Elan, but I'm not sure.

In principle, we should try to do better at identifying CPUID-less
CPUs in early boot, but that's more complicated.

Reported-by: One Thousand Gnomes <gnomes@xxxxxxxxxxxxxxxxxxx>
Cc: Matthew Whitehead <tedheadster@xxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
---
 arch/x86/boot/cpu.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/arch/x86/boot/cpu.c b/arch/x86/boot/cpu.c
index 4224ede43b4e..26240dde081e 100644
--- a/arch/x86/boot/cpu.c
+++ b/arch/x86/boot/cpu.c
@@ -87,12 +87,6 @@ int validate_cpu(void)
                return -1;
        }
 
-       if (CONFIG_X86_MINIMUM_CPU_FAMILY <= 4 && !IS_ENABLED(CONFIG_M486) &&
-           !has_eflag(X86_EFLAGS_ID)) {
-               printf("This kernel requires a CPU with the CPUID instruction.  
Build with CONFIG_M486=y to run on this CPU.\n");
-               return -1;
-       }
-
        if (err_flags) {
                puts("This kernel requires the following features "
                     "not present on the CPU:\n");
-- 
2.9.3


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