Re: [Xen-devel] [PATCH v5 6/9] libxc: create unmapped initrd in domain builder if supported

[Juergen Gross <jgross@xxxxxxxx>]

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


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