linux-kernel - Re: [5.0.0 rc3 BUG] possible irq lock inversion dependency detected

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Message-ID: <alpine.DEB.2.21.1904141948200.4917@nanos.tec.linutronix.de>
Date:   Sun, 14 Apr 2019 19:51:06 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>
cc:     Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        thomas.lendacky@....com
Subject: Re: [5.0.0 rc3 BUG] possible irq lock inversion dependency
 detected

Hi,

On Sun, 14 Apr 2019, Mikhail Gavrilov wrote:

> This bug is still present in 5.1 rc4
> Why no one answered me?

Because mails fall through the cracks occasionally.

Does the patch below cure your problem?

Thanks,

	tglx

8<------------------
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -426,6 +426,8 @@ static __always_inline void __speculatio
 	u64 msr = x86_spec_ctrl_base;
 	bool updmsr = false;
 
+	lockdep_assert_irqs_disabled();
+
 	/*
 	 * If TIF_SSBD is different, select the proper mitigation
 	 * method. Note that if SSBD mitigation is disabled or permanentely
@@ -477,10 +479,12 @@ static unsigned long speculation_ctrl_up
 
 void speculation_ctrl_update(unsigned long tif)
 {
+	unsigned long flags;
+
 	/* Forced update. Make sure all relevant TIF flags are different */
-	preempt_disable();
+	local_irq_save(flags);
 	__speculation_ctrl_update(~tif, tif);
-	preempt_enable();
+	local_irq_restore(flags);
 }
 
 /* Called from seccomp/prctl update */