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Date: Thu, 22 Aug 2024 07:32:38 +0200
From: Christoph Hellwig <hch@lst.de>
To: LEROY Christophe <christophe.leroy2@cs-soprasteria.com>
Cc: Christian Lamparter <christian.lamparter@isd.uni-stuttgart.de>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
	Stan Johnson <userm57@yahoo.com>,
	Finn Thain <fthain@linux-m68k.org>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v2] powerpc: warn on emulation of dcbz instruction in
 kernel mode
Message-ID: <20240822053238.GA2028@lst.de>
References: <2e3acfe63d289c6fba366e16973c9ab8369e8b75.1631803922.git.christophe.leroy@csgroup.eu> <17fa6450-6613-4c34-804b-e47246e7b39c@isd.uni-stuttgart.de> <9dbf73fe-a459-4956-8dbc-e919d9728f5e@cs-soprasteria.com>
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On Thu, Aug 22, 2024 at 05:25:10AM +0000, LEROY Christophe wrote:
> > and this results in a call to dma_direct_allocation(), which has one
> > innocent looking memset():
> 
> 
> memset() can't be used on non-cached memory, memset_io() has to be used
> instead.

No, we use memset on uncached memory all the time.  Note that uncached
memory != __iomem memory, for which you DO have to use memset_io.