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Date: Mon, 10 Apr 2017 11:29:39 +0100
From: Mark Rutland <>
To: Peter Zijlstra <>
Cc: Mathias Krause <>,
	Thomas Gleixner <>,
	Andy Lutomirski <>,
	Kees Cook <>,
	Andy Lutomirski <>,
	"" <>,
	Hoeun Ryu <>, PaX Team <>,
	Emese Revfy <>,
	Russell King <>, X86 ML <>,
	"" <>,
	"" <>
Subject: Re: Re: [RFC v2][PATCH 04/11] x86: Implement

On Fri, Apr 07, 2017 at 04:45:26PM +0200, Peter Zijlstra wrote:
> On Fri, Apr 07, 2017 at 12:51:15PM +0200, Mathias Krause wrote:
> > Why that? It allows fast and CPU local modifications of r/o memory.
> > OTOH, an approach that needs to fiddle with page table entries
> > requires global synchronization to keep the individual TLB states in
> > sync. Hmm.. Not that fast, I'd say.
> The fixmaps used for kmap_atomic are per-cpu, no global sync required.

That might be fine for x86, but for some architectures fixmap slots and
kmap_atomic mappings happen to be visible to other CPUs even if they're
not required to be.

Using an mm solves that for all, though.


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