linux-kernel - Re: Overlapping ioremap() calls, set_memory

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Date:	Sat, 16 Apr 2016 11:20:18 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Toshi Kani <toshi.kani@....com>
Cc:	"Luis R. Rodriguez" <mcgrof@...nel.org>,
	"Maciej W. Rozycki" <macro@...ux-mips.org>,
	Julia Lawall <julia.lawall@...6.fr>,
	Toshi Kani <toshi.kani@...com>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Dave Airlie <airlied@...hat.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-arch@...r.kernel.org, X86 ML <x86@...nel.org>,
	Daniel Vetter <daniel.vetter@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	Brian Gerst <brgerst@...il.com>
Subject: Re: Overlapping ioremap() calls, set_memory_*() semantics


* Toshi Kani <toshi.kani@....com> wrote:

> On x86, ioremap() and remap_pfn_range() already fail on a conflicting cache
> type if it is not allowed by the rule defined in is_new_memtype_allowed().
>  This exception handling is necessary for remap_pfn_range() called by
> /dev/mem, but I do not think it's necessary for ioremap().  I think we can
> start from adding a warning message to ioremap().

Agreed, we should warn and map the situation before doing any behavioral change 
that isn't a fix.

Thanks,

	Ingo