linux-kernel - Re: [PATCH 6/6] x86: Fix stray A/D bit setting into non-present PTEs

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Message-ID: <CA+55aFydq3kpT-mzPqcU1_1h=+vSUj6RmQwiz5NVnfY4HfSjXw@mail.gmail.com>
Date:	Thu, 30 Jun 2016 22:43:09 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Dave Hansen <dave@...1.net>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Andi Kleen <ak@...ux.intel.com>,
	Michal Hocko <mhocko@...e.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH 6/6] x86: Fix stray A/D bit setting into non-present PTEs

On Thu, Jun 30, 2016 at 9:39 PM, Dave Hansen <dave@...1.net> wrote:
>
> I think what you suggest will work if we don't consider A/D in
> pte_none().  I think there are a bunch of code path where assume that
> !pte_present() && !pte_none() means swap.

Yeah, we would need to change pte_none() to mask off D/A, but I think
that might be the only real change needed (other than making sure that
we don't use the bits in the swap entries, I didn't look at that part
at all)

           Linus