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Date: Wed, 27 Sep 2017 13:49:10 +0200
From: Cornelia Huck <cohuck@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v1 0/6] s390x/tcg: fix some accesses using
 low address
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To: David Hildenbrand <david@redhat.com>
Cc: qemu-devel@nongnu.org, thuth@redhat.com, Christian Borntraeger <borntraeger@de.ibm.com>, Alexander Graf <agraf@suse.de>, Richard Henderson <rth@twiddle.net>

On Tue, 26 Sep 2017 20:33:12 +0200
David Hildenbrand <david@redhat.com> wrote:

> Conny reported that a guest Linux currently spits out:
>   "The s390-virtio transport is deprecated. Please switch to a modern host
>   providing virtio-ccw."
> 
> This is strange, because we have no legacy virtio transport in QEMU :)
> 
> Main problem is, that a page is tested for acccess, and the test does not
> fail. All memory access variants like stb_phys() will never fail. On
> invalid memory, they simply do nothing.
> 
> Linux uses lura for this check. Let's introduce a _real MMU that handles
> prefixing and can later be used for things like low address protection.
> 
> The other BUG is that a check for invalid memory is wrong. Therefore,
> Patch 1 alone makes the guest crash when trying to initialize the
> virtio transport. Crazy stuff.

Indeed, thanks for hunting this down! No strange messages for me any
more :)

Fixed up the empty line in lura and applied to s390-next.