x86/apic: Make x2apic_disable() work correctly

x2apic_disable() clears x2apic_state and x2apic_mode unconditionally, even
when the state is X2APIC_ON_LOCKED, which prevents the kernel to disable
it thereby creating inconsistent state.

Due to the early state check for X2APIC_ON, the code path which warns about
a locked X2APIC cannot be reached.

Test for state < X2APIC_ON instead and move the clearing of the state and
mode variables to the place which actually disables X2APIC.

[ tglx: Massaged change log. Added Fixes tag. Moved clearing so it's at the
  	right place for back ports ]

Fixes: a57e456a7b28 ("x86/apic: Fix fallout from x2apic cleanup")
Signed-off-by: Yuntao Wang <yuntao.wang@linux.dev>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20240813014827.895381-1-yuntao.wang@linux.dev

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 66fd4b2a37a3a59197730c2f030cb47957ec8224..373638691cd480a392d7f10548f1640708ad75dc 100644 (file)
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1775,12 +1775,9 @@ static __init void apic_set_fixmap(bool read_apic);
 
 static __init void x2apic_disable(void)
 {
-       u32 x2apic_id, state = x2apic_state;
+       u32 x2apic_id;
 
-       x2apic_mode = 0;
-       x2apic_state = X2APIC_DISABLED;
-
-       if (state != X2APIC_ON)
+       if (x2apic_state < X2APIC_ON)
                return;
 
        x2apic_id = read_apic_id();
@@ -1793,6 +1790,10 @@ static __init void x2apic_disable(void)
        }
 
        __x2apic_disable();
+
+       x2apic_mode = 0;
+       x2apic_state = X2APIC_DISABLED;
+
        /*
         * Don't reread the APIC ID as it was already done from
         * check_x2apic() and the APIC driver still is a x2APIC variant,