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Date:   Wed, 29 Jan 2020 09:09:39 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Christian Borntraeger <borntraeger@de.ibm.com>
Cc:     Christopher Lameter <cl@linux.com>,
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        linux-kernel@vger.kernel.org, David Windsor <dave@nullcore.net>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
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        Michal Kubecek <mkubecek@suse.cz>
Subject: Re: [kernel-hardening] [PATCH 09/38] usercopy: Mark kmalloc caches
 as usercopy caches
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On Wed, Jan 29, 2020 at 06:07:14PM +0100, Christian Borntraeger wrote:
> > DMA can be done to NORMAL memory as well.
> 
> Exactly. 
> I think iucv uses GFP_DMA because z/VM needs those buffers to reside below 2GB (which is ZONA_DMA for s390).

The normal way to allocate memory with addressing limits would be to
use dma_alloc_coherent and friends.  Any chance to switch iucv over to
that?  Or is there no device associated with it?