x86/bootflag: Micro-optimize sbf_write()

Change parity bit with XOR when !parity instead of masking bit out
and conditionally setting it when !parity.

Saves a couple of bytes in the object file.

Co-developed-by: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250226153709.6370-1-ubizjak@gmail.com

diff --git a/arch/x86/kernel/bootflag.c b/arch/x86/kernel/bootflag.c
index 4d89a2d80d0f3736aec3fff675b090e8fb54eef2..b935c3e42bfdffef2924a7cf26f326fc0b306e55 100644 (file)
--- a/arch/x86/kernel/bootflag.c
+++ b/arch/x86/kernel/bootflag.c
@@ -38,9 +38,8 @@ static void __init sbf_write(u8 v)
        unsigned long flags;
 
        if (sbf_port != -1) {
-               v &= ~SBF_PARITY;
                if (!parity(v))
-                       v |= SBF_PARITY;
+                       v ^= SBF_PARITY;
 
                printk(KERN_INFO "Simple Boot Flag at 0x%x set to 0x%x\n",
                        sbf_port, v);