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Date: Mon, 3 Feb 2020 09:36:22 -0800
From: Christoph Hellwig <hch@...radead.org>
To: Christian Borntraeger <borntraeger@...ibm.com>
Cc: Christoph Hellwig <hch@...radead.org>,
Christopher Lameter <cl@...ux.com>,
Kees Cook <keescook@...omium.org>, Jiri Slaby <jslaby@...e.cz>,
Julian Wiedmann <jwi@...ux.ibm.com>,
Ursula Braun <ubraun@...ux.ibm.com>,
Alexander Viro <viro@...iv.linux.org.uk>,
linux-kernel@...r.kernel.org, David Windsor <dave@...lcore.net>,
Pekka Enberg <penberg@...nel.org>,
David Rientjes <rientjes@...gle.com>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-xfs@...r.kernel.org,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andy Lutomirski <luto@...nel.org>,
"David S. Miller" <davem@...emloft.net>,
Laura Abbott <labbott@...hat.com>,
Mark Rutland <mark.rutland@....com>,
"Martin K. Petersen" <martin.petersen@...cle.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Christoffer Dall <christoffer.dall@...aro.org>,
Dave Kleikamp <dave.kleikamp@...cle.com>, Jan Kara <jack@...e.cz>,
Luis de Bethencourt <luisbg@...nel.org>,
Marc Zyngier <marc.zyngier@....com>, Rik van Riel <riel@...hat.com>,
Matthew Garrett <mjg59@...gle.com>, linux-fsdevel@...r.kernel.org,
linux-arch@...r.kernel.org, netdev@...r.kernel.org,
kernel-hardening@...ts.openwall.com,
Vlastimil Babka <vbabka@...e.cz>, Michal Kubecek <mkubecek@...e.cz>
Subject: Re: [PATCH 09/38] usercopy: Mark kmalloc caches
as usercopy caches
On Wed, Jan 29, 2020 at 06:19:56PM +0100, Christian Borntraeger wrote:
> There is not necessarily a device for that. It is a hypervisor interface (an
> instruction that is interpreted by z/VM). We do have the netiucv driver that
> creates a virtual nic, but there is also AF_IUCV which works without a device.
>
> But back to the original question: If we mark kmalloc caches as usercopy caches,
> we should do the same for DMA kmalloc caches. As outlined by Christoph, this has
> nothing to do with device DMA.
Oh well, s/390 with its weird mix of cpu and I/O again. Everywhere else
where we have addressing limits we do treat that as a DMA address.
We've also had a bit of a lose plan to force ZONE_DMA as a public
interface out, as it is generally the wrong thing to do for drivers.
A ZONE_32 and/or ZONE_31 makes some sense as the backing for the
dma allocator, but it mostly shouldn't be exposed, especially not to
the slab allocator.
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