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Message-ID: <20171115145835.GB319@bombadil.infradead.org>
Date: Wed, 15 Nov 2017 06:58:35 -0800
From: Matthew Wilcox <willy@...radead.org>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Tycho Andersen <tycho@...ker.com>, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, kernel-hardening@...ts.openwall.com,
Marco Benatto <marco.antonio.780@...il.com>,
Juerg Haefliger <juerg.haefliger@...onical.com>, x86@...nel.org
Subject: Re: [PATCH v6 03/11] mm, x86: Add support for eXclusive Page Frame
Ownership (XPFO)
On Tue, Nov 14, 2017 at 11:00:20PM -0800, Dave Hansen wrote:
> On 11/14/2017 07:44 PM, Matthew Wilcox wrote:
> > We don't need to kmap in order to access MOVABLE allocations. kmap is
> > only needed for HIGHMEM allocations. So there's nothing wrong with ext4
> > or set_bh_page().
>
> Yeah, it's definitely not _buggy_.
>
> Although, I do wonder what we should do about these for XPFO. Should we
> just stick a kmap() in there and comment it? What we really need is a
> mechanism to say "use this as a kernel page" and "stop using this as a
> kernel page". kmap() does that... kinda. It's not a perfect fit, but
> it's pretty close.
It'd be kind of funny if getting XPFO working better means improving
how well Linux runs on 32-bit machines with HIGHMEM. I think there's
always going to be interest in those -- ARM developed 36 bit physmem
before biting the bullet and going to arm64. Maybe OpenRISC will do
that next ;-)
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