From mboxrd@z Thu Jan  1 00:00:00 1970
From: Olaf Hering <olaf@aepfle.de>
Subject: Re: 4.2 TODO update
Date: Tue, 14 Feb 2012 16:18:03 +0100
Message-ID: <20120214151803.GA22116@aepfle.de>
References: <mailman.3388.1329129411.1471.xen-devel@lists.xensource.com>
	<f56b9a9d22ed4bc42e77212c43b364ec.squirrel@webmail.lagarcavilla.org>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xensource.com>
Content-Disposition: inline
In-Reply-To: <f56b9a9d22ed4bc42e77212c43b364ec.squirrel@webmail.lagarcavilla.org>
List-Unsubscribe: <http://lists.xensource.com/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xensource.com>
List-Help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-Subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
Sender: xen-devel-bounces@lists.xensource.com
Errors-To: xen-devel-bounces@lists.xensource.com
To: Andres Lagar-Cavilla <andres@lagarcavilla.org>
Cc: xen-devel@lists.xensource.com, tim@xen.org, ian.campbell@citrix.com
List-Id: xen-devel@lists.xenproject.org

On Tue, Feb 14, Andres Lagar-Cavilla wrote:

> Why? Because it's really really hard to guarantee we'll go to sleep in an
> atomic context. The main use for wait queues (imho) is in hvm_copy, and
> there's a zillion paths going into hvm_copy (copy_from/to_user!) with all
> ways of bumping the preemption count.

If the guests pagetable is paged out this code path will trigger, then
one of the hypercalls returns an error and the guest runs into a BUG().
I think it was decrease_reservation, or similar.
Another thing reported by Huawei on this list was somewhere in the
emulation code where a gfn_to_mfn() failed.

What other way exist to make paging 100% transparent to the guest?

Olaf