x86/Kconfig: Limit NR_CPUS on 32-bit to a sane amount

The recent cpu_entry_area changes fail to compile on 32-bit when BIGSMP=y
and NR_CPUS=512, because the fixmap area becomes too big.

Limit the number of CPUs with BIGSMP to 64, which is already way to big for
32-bit, but it's at least a working limitation.

We performed a quick survey of 32-bit-only machines that might be affected
by this change negatively, but found none.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 665eba1b610393f122d1ddca1ad950d40a5be7cf..cd5199de231e68a969984b47d4875fb1884a788c 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -925,7 +925,8 @@ config MAXSMP
 config NR_CPUS
        int "Maximum number of CPUs" if SMP && !MAXSMP
        range 2 8 if SMP && X86_32 && !X86_BIGSMP
-       range 2 512 if SMP && !MAXSMP && !CPUMASK_OFFSTACK
+       range 2 64 if SMP && X86_32 && X86_BIGSMP
+       range 2 512 if SMP && !MAXSMP && !CPUMASK_OFFSTACK && X86_64
        range 2 8192 if SMP && !MAXSMP && CPUMASK_OFFSTACK && X86_64
        default "1" if !SMP
        default "8192" if MAXSMP