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List:       linux-s390
Subject:    Re: [PATCH v4 1/6] virtio-net: Stop doing DMA from the stack
From:       Andy Lutomirski <luto () amacapital ! net>
Date:       2015-10-31 5:02:17
Message-ID: CALCETrVvoAfQSUGhquNHEK1sSuAz=8QXp8OGAE+rjX207vS_-w () mail ! gmail ! com
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On Fri, Oct 30, 2015 at 6:55 AM, Christian Borntraeger
<borntraeger@de.ibm.com> wrote:
> Am 30.10.2015 um 02:09 schrieb Andy Lutomirski:
> > From: "Michael S. Tsirkin" <mst@redhat.com>
> > 
> > Once virtio starts using the DMA API, we won't be able to safely DMA
> > from the stack.  virtio-net does a couple of config DMA requests
> > from small stack buffers -- switch to using dynamically-allocated
> > memory.
> > 
> > This should have no effect on any performance-critical code paths.
> > 
> > [I wrote the subject and commit message.  mst wrote the code. --luto]
> > 
> > Signed-off-by: Andy Lutomirski <luto@kernel.org>
> > signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> 
> I still get an error when using multiqueue:
> 
> #  ethtool -L eth0 combined 4
> [   33.534686] virtio_ccw 0.0.000d: DMA-API: device driver maps memory from stack \
> [addr=00000000629e7c06]

Fixed in my branch, I think.

--Andy
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