linux-kernel - Re: [PATCH v2] x86/mm: avoid premature success when changing page attributes

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Date:	Tue, 02 Feb 2016 01:46:17 -0700
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Ingo Molnar" <mingo@...nel.org>
Cc:	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>, <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	<linux-kernel@...r.kernel.org>, <hpa@...or.com>
Subject: Re: [PATCH v2] x86/mm: avoid premature success when changing
 page attributes

>>> On 28.01.16 at 09:42, <mingo@...nel.org> wrote:
> Could we try a v3?

Okay, I withdraw the patch: Upon further consideration it is note
really clear what the intended behavior of set_memory_*() on
address ranges with mapping holes is supposed to be. The original
issue was with set_memory_nx() (called from mark_rodata_ro())
stumbling across an unmapped region (resulting from an out of
tree change completely unmapping the kernel mappings of
address ranges passed to free_init_pages()). I simply don't have
the time to check whether the unmapping done with
CONFIG_DEBUG_PAGEALLOC would have a similar effect. The
net result in any event were pages (past the hole) reported as
problematic when CONFIG_DEBUG_WX is enabled.

Jan