linux-kernel - Re: [PATCH] x86/mm: disable preemption during CR3 read+write

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Message-ID: <c0a89331-e6f1-5c71-b513-2ff55de392d4@linutronix.de>
Date:	Fri, 5 Aug 2016 17:52:38 +0200
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>, Borislav Petkov <bp@...e.de>,
	Andy Lutomirski <luto@...nel.org>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] x86/mm: disable preemption during CR3 read+write

On 08/05/2016 05:42 PM, Andy Lutomirski wrote:
> 
> This should affect kernel threads too, right?

I don't think so because they don't have a MM in the first place so
they don't shouldn't need to flush a TLB. But then there is iounmap()
and vfree() for instance which does

vmap_debug_free_range()
{
   if (debug_pagealloc_enabled()) {
         vunmap_page_range(start, end);
         flush_tlb_kernel_range(start, end);
   }
}

so it looks like a candidate.

> Acked-by: Andy Lutomirski <luto@...nel.org>

Sebastian