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Subject: Re: [PATCH v6 03/11] mm, x86: Add support for eXclusive Page Frame
 Ownership (XPFO)
To: Tycho Andersen <tycho@docker.com>
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Cc: Yisheng Xie <xieyisheng1@huawei.com>,
        Juerg Haefliger <juerg.haefliger@canonical.com>,
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From: Dave Hansen <dave.hansen@intel.com>
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Date: Wed, 20 Sep 2017 17:04:35 -0700
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On 09/20/2017 05:02 PM, Tycho Andersen wrote:
> ...and makes it easier to pair tlb flushes with changing the
> protections. I guess we still need the for loop, because we need to
> set/unset the xpfo bits as necessary, but I'll switch it to a single
> set_kpte(). This also implies that the xpfo bits should all be the
> same on every page in the mapping, which I think is true.

FWIW, it's a bit bonkers to keep all this duplicate xpfo metadata for
compound pages.  You could probably get away with only keeping it for
the head page.