From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: virtio balloon: do not call blocking ops when !TASK_RUNNING
Date: Thu, 26 Feb 2015 09:30:31 +0100
Message-ID: <20150226083031.GA24184@redhat.com>
References: <20150225111318.0040536b@oc7435384737.ibm.com>
	<87y4nllb85.fsf@rustcorp.com.au>
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To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Peter Zijlstra <peterz@infradead.org>, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org
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On Thu, Feb 26, 2015 at 11:50:42AM +1030, Rusty Russell wrote:
> Thomas Huth <thuth@linux.vnet.ibm.com> writes:
> >  Hi all,
> >
> > with the recent kernel 3.19, I get a kernel warning when I start my
> > KVM guest on s390 with virtio balloon enabled:
> 
> The deeper problem is that virtio_ccw_get_config just silently fails on
> OOM.
> 
> Neither get_config nor set_config are expected to fail.
> 
> Cornelia, I think ccw and config_area should be allocated inside vcdev.
> You could either use pointers, or simply allocate vcdev with GDP_DMA.
> 
> This would avoid the kmalloc inside these calls.
> 
> Thanks,
> Rusty.

But it won't solve the problem of nested sleepers
with ccw: ATM is invokes ccw_io_helper to execute
commands, and that one calls wait_event
to wait for an interrupt.

Might be fixable but I think my patch looks like a safer
solution for 4.0/3.19, no?

-- 
MST