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Date: Sun, 14 Jan 2018 13:54:44 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Greg KH <greg@kroah.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-kernel@vger.kernel.org, Vince Weaver <vince@deater.net>,
        torvalds@linux-foundation.org, robert@swiecki.net,
        luto@amacapital.net, hughd@google.com,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>
Subject: Re: [PATCH] x86,perf: Disable intel_bts when PTI
Message-ID: <20180114125444.uqr53c6ryfn5hd53@gmail.com>
References: <20180114102713.GB6166@worktop.programming.kicks-ass.net>
 <20180114105003.GA30927@kroah.com>
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* Greg KH <greg@kroah.com> wrote:

> On Sun, Jan 14, 2018 at 11:27:13AM +0100, Peter Zijlstra wrote:
> > 
> > The intel_bts driver does not use the 'normal' BTS buffer we allocated
> > space for in the cpu_entry_area but instead uses the memory allocated
> > for the perf AUX buffer.
> > 
> > This obviously comes apart when using PTI because then the kernel
> > mapping; which includes that AUX buffer memory; disappears.
> > 
> > For now disable this driver when PTI is enabled, we'll try and sort
> > something out later.
> > 
> > Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> > Reported-by: Vince Weaver <vincent.weaver@maine.edu>
> > Reported-by: Robert Święcki <robert@swiecki.net>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> 
> Can you add a:
> 	Cc: stable <stable@vger.kernel.org>
> please?

Note that these fixes are all going into tip:x86/pti, which is still a backporting 
friendly linear set of commits that should all be backported.

So once 99a9dc98ba52 goes upstream, all of v4.14..99a9dc98ba52 the remaining bits 
can go to -stable as well.

Will keep you updated about the latest status periodically, right now the latest 
that is already upstream is:

  de791821c295: x86/pti: Rename BUG_CPU_INSECURE to BUG_CPU_MELTDOWN

i.e. all 194 commits in the v4.14..de791821c295 range should be queued up for 
-stable. (And most of them already are.)

There are 28 new commits in tip:x86/pti that will (hopefully) go upstream later 
today.

Thanks,

	Ingo