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Date:   Fri, 6 Nov 2020 20:31:49 +0000
From:   Fenghua Yu <fenghua.yu@intel.com>
To:     Xiaoyao Li <xiaoyao.li@linux.intel.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Tony Luck <tony.luck@intel.com>,
        Christopherson Sean J <sean.j.christopherson@intel.com>,
        Ashok Raj <ashok.raj@intel.com>,
        Ravi V Shankar <ravi.v.shankar@intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>
Subject: Re: [PATCH RFC v3 2/4] x86/bus_lock: Handle warn and fatal in #DB
 for bus lock
Message-ID: <20201106203149.GA4097366@otcwcpicx6.sc.intel.com>
References: <20201031002714.3649728-1-fenghua.yu@intel.com>
 <20201031002714.3649728-3-fenghua.yu@intel.com>
 <21d0415c-9af4-db18-8e65-410f6ab5ec68@linux.intel.com>
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In-Reply-To: <21d0415c-9af4-db18-8e65-410f6ab5ec68@linux.intel.com>
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Hi, Xiaoyao,

On Tue, Nov 03, 2020 at 08:15:27PM +0800, Xiaoyao Li wrote:
> On 10/31/2020 8:27 AM, Fenghua Yu wrote:
> > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> > index 3c70fb34028b..1c3442000972 100644
> > --- a/arch/x86/kernel/traps.c
> > +++ b/arch/x86/kernel/traps.c
> > @@ -953,6 +953,13 @@ static __always_inline void exc_debug_user(struct pt_regs *regs,
> >   		goto out_irq;
> >   	}
> > +	/*
> > +	 * Handle bus lock. #DB for bus lock can only be triggered from
> > +	 * userspace.
> > +	 */
> > +	if (!(dr6 & DR_BUS_LOCK))
> 
> it should be
> 
> 	if (dr6 & DR_BUS_LOCK)
> 
> since you keep DR6.[bit 11] reserved in this version. bit 11 of
> debug_read_clear_dr6() being set to 1 means bus lock detected.

You are right. Will fix it in the next version.

Thank you very much!

-Fenghua