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Subject: Re: [RFC PATCH 1/2] x86/ibpb: Skip IBPB when we switch back to same
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To:     Tim Chen <tim.c.chen@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
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        David Woodhouse <dwmw@amazon.co.uk>,
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From:   Arjan van de Ven <arjan@linux.intel.com>
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Date:   Thu, 25 Jan 2018 11:34:13 -0800
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> 
> This patch tries to address the case when we do switch to init_mm and back.
> Do you still have objections to the approach in this patch
> to save the last active mm before switching to init_mm?

how do you know the last active mm did not go away and started a new process with new content?
(other than taking a reference which has other side effects)