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Date: Wed, 19 Sep 2012 17:57:26 +0300
From: Avi Kivity <avi@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2 7/7] s390/kvm: In-kernel channel
	subsystem support.
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To: Alexander Graf <agraf@suse.de>
Cc: linux-s390 <linux-s390@vger.kernel.org>, Anthony Liguori <aliguori@us.ibm.com>, Rusty Russell <rusty@rustcorp.com.au>, KVM <kvm@vger.kernel.org>, Carsten Otte <cotte@de.ibm.com>, Sebastian Ott <sebott@linux.vnet.ibm.com>, Marcelo Tosatti <mtosatti@redhat.com>, Heiko Carstens <heiko.carstens@de.ibm.com>, qemu-devel <qemu-devel@nongnu.org>, Christian Borntraeger <borntraeger@de.ibm.com>, Cornelia Huck <cornelia.huck@de.ibm.com>, Martin Schwidefsky <schwidefsky@de.ibm.com>

On 09/19/2012 05:47 PM, Alexander Graf wrote:
> 
> On 04.09.2012, at 17:13, Cornelia Huck wrote:
> 
>> Handle most support for channel I/O instructions in the kernel itself.
>> 
>> Only asynchronous functions (such as the start function) need to be
>> handled by userspace.
> 
> Phew. This is a lot of code for something that is usually handled in user space in the kvm world. The x86 equivalent would be an in-kernel PCI bus, right? Have you measured major performance penalties when running this from user space?
> 
> Avi, what do you think?

I know nothing of this stuff.  But your request for numbers is justified
of course.



-- 
error compiling committee.c: too many arguments to function