linux-kernel - [tip: x86/urgent] x86/apic: Make x2apic

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Message-ID: <172355531145.2215.1265281947968550641.tip-bot2@tip-bot2>
Date: Tue, 13 Aug 2024 13:21:51 -0000
From: "tip-bot2 for Yuntao Wang" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Yuntao Wang <yuntao.wang@...ux.dev>, Thomas Gleixner <tglx@...utronix.de>,
 stable@...r.kernel.org, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/urgent] x86/apic: Make x2apic_disable() work correctly

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     0ecc5be200c84e67114f3640064ba2bae3ba2f5a
Gitweb:        https://git.kernel.org/tip/0ecc5be200c84e67114f3640064ba2bae3ba2f5a
Author:        Yuntao Wang <yuntao.wang@...ux.dev>
AuthorDate:    Tue, 13 Aug 2024 09:48:27 +08:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Tue, 13 Aug 2024 15:15:19 +02:00

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@...ux.dev>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/all/20240813014827.895381-1-yuntao.wang@linux.dev

---
 arch/x86/kernel/apic/apic.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 66fd4b2..3736386 100644
--- 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,