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Date: Sat, 3 Mar 2018 09:54:54 +0100
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH 0/2] Backport IBPB on context switch to non-dumpable
 process
Message-ID: <20180303085454.GA23988@kroah.com>
References: <cover.1520026221.git.tim.c.chen@linux.intel.com>
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To: Tim Chen <tim.c.chen@linux.intel.com>
Cc: stable@vger.kernel.org, Andy Lutomirski <luto@kernel.org>, Nadav Amit <nadav.amit@gmail.com>, Thomas Gleixner <tglx@linutronix.de>, Andrew Morton <akpm@linux-foundation.org>, Arjan van de Ven <arjan@linux.intel.com>, Borislav Petkov <bp@alien8.de>, Dave Hansen <dave.hansen@intel.com>, Linus Torvalds <torvalds@linux-foundation.org>, Mel Gorman <mgorman@suse.de>, Peter Zijlstra <peterz@infradead.org>, Rik van Riel <riel@redhat.com>, Ingo Molnar <mingo@kernel.org>, David Woodhouse <dwmw@amazon.co.uk>, ak@linux.intel.com, karahmed@amazon.de, pbonzini@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org

On Fri, Mar 02, 2018 at 01:32:08PM -0800, Tim Chen wrote:
> Greg,
> 
> I will like to propose backporting "x86/speculation: Use Indirect Branch
> Prediction Barrier on context switch" from commit 18bf3c3e in upstream
> to 4.9 and 4.4 stable.  The patch has already been ported to 4.14 and
> 4.15 stable.  The patch needs mm context id that Andy added in commit
> f39681ed. I have lifted the mm context id change from Andy's upstream
> patch and included it here.

What does this patch "fix" in those older kernels?  Is this a
performance improvement or something else?

thanks,

greg k-h

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