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From: Ingo Molnar <mingo@kernel.org>
To: Chenyi Qiang <chenyi.qiang@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Tony Luck <tony.luck@intel.com>,
	Fenghua Yu <fenghua.yu@intel.com>,
	linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [RESEND] x86/bus_lock: Don't assume the init value of DEBUGCTLMSR.BUS_LOCK_DETECT to be zero
Date: Tue, 2 Aug 2022 13:42:45 +0200	[thread overview]
Message-ID: <YukNtYnGg4FgAsOi@gmail.com> (raw)
In-Reply-To: <897aa91c-9d45-e16a-9b09-849fab588cd7@intel.com>


* Chenyi Qiang <chenyi.qiang@intel.com> wrote:

> 
> 
> On 8/2/2022 6:51 PM, Ingo Molnar wrote:
> > 
> > * Chenyi Qiang <chenyi.qiang@intel.com> wrote:
> > 
> > > It's possible that BIOS/firmware has set DEBUGCTLMSR_BUS_LOCK_DETECT, or
> > > this kernel has been kexec'd from a kernel that enabled bus lock
> > > detection.
> > > 
> > > Disable bus lock detection explicitly if not wanted.
> > 
> > Makes sense.
> > 
> > Just curious: in what circumstances does the BIOS/firmware set
> > DEBUGCTLMSR_BUS_LOCK_DETECT? Does it use it, or does it enable it for some
> > spurious reason, without really using the feature? (Assuming you are aware
> > of instances where this happened - or was this simply a hypothetical?)
> 
> Yes, It's just a hypothetical for BIOS/firmware. Kexec is the real case I
> met with this problem.

Fair enough, I've tweaked the changelog a bit to de-emphasize the firmware 
angle, and applied your fix to tip:x86/urgent.

Thanks,

	Ingo

  reply	other threads:[~2022-08-02 11:42 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-02  3:32 [RESEND] x86/bus_lock: Don't assume the init value of DEBUGCTLMSR.BUS_LOCK_DETECT to be zero Chenyi Qiang
2022-08-02 10:51 ` Ingo Molnar
2022-08-02 11:29   ` Chenyi Qiang
2022-08-02 11:42     ` Ingo Molnar [this message]
2022-08-02 11:57 ` [tip: x86/urgent] " tip-bot2 for Chenyi Qiang

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