From mboxrd@z Thu Jan  1 00:00:00 1970
From: Juergen Gross <jgross@suse.com>
Subject: Re: [PATCH v5 6/9] libxc: create unmapped initrd in
 domain builder if supported
Date: Thu, 26 Nov 2015 06:19:05 +0100
Message-ID: <56569649.40204@suse.com>
References: <1447335816-31772-1-git-send-email-jgross@suse.com>
	<1447335816-31772-7-git-send-email-jgross@suse.com>
	<5655DDDC.5000005@oracle.com> <56569353.4050709@suse.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
In-Reply-To: <56569353.4050709@suse.com>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>, xen-devel@lists.xen.org, Ian.Campbell@citrix.com, ian.jackson@eu.citrix.com, stefano.stabellini@eu.citrix.com, wei.liu2@citrix.com, roger.pau@citrix.com
List-Id: xen-devel@lists.xenproject.org

On 26/11/15 06:06, Juergen Gross wrote:
> On 25/11/15 17:12, Boris Ostrovsky wrote:
>> On 11/12/2015 08:43 AM, Juergen Gross wrote:
>>> In case the kernel of a new pv-domU indicates it is supporting an
>>> unmapped initrd, don't waste precious virtual space for the initrd,
>>> but allocate only guest physical memory for it.
>>
>> This patch breaks 32-bit pygrub.
>>
>> I am not 100% sure yet but it may be that only 64-bit guests are affected.
>>
>> With RHEL5 I get
>>     initrd extends beyond end of memory (0x780080eda000 > 0x40000000)
> 
> Let me summarize your findings:
> 
> You are using a 32 bit dom0 to start a 64 bit RHEL5 guest via pygrub
> (not pvgrub). The guest then barfs about the initrd position in
> memory.
> 
> Can you get the debug output of the domain builder? This would help
> to see what is really happening.

I think I have found a potential problem not (directly) related to my
patch:

The domain builder is using xen_pfn_t for pfns. With a 32 bit toolstack
this will lead to problems with 64 bit guests, as xen_pfn_t on x86 is:

typedef unsigned long xen_pfn_t;

I guess we have to modify the domain builder to use a 64 bit type
instead.


Juergen